The Forgotten Archosaurs

A New Aetosaur

2012-01-19T15:35:00.000-05:00

Julia B. Desojo, Martin D. Ezcurra, and Edio E. Kischlat. 2012. "A new aetosaur genus (Archosauria: Pseudosuchia) from the early Late Triassic of southern Brazil" Zootaxa 3166: 1–33

Abstract
We describe the new aetosaur Aetobarbakinoides brasiliensis gen. et sp. nov. from the early Late Triassic (late Carnian - early Norian) Brazilian Santa Maria Formation. The holotype is composed of a partial postcranium including several cervical and dorsal vertebrae and ribs, one anterior caudal vertebra, right scapula, right humerus, right tibia, partial right pes, and anterior and mid-dorsal paramedian osteoderms. Aetobarbakinoides is differentiated from other aetosaurs by the presence of cervical vertebrae with widely laterally extended prezygapophyses, mid-cervical vertebrae with anterior articular facet width more than 1.2 times wider than the posterior one, anterior caudal vertebrae with extremely anteroposteriorly short prezygapophyses, elongated humerus and tibia in relation to the axial skeleton, and paramedian osteoderms with a weakly raised anterior bar. A cladistic analysis recovered the new species as more derived than the South American genera Aetosauroides (late Carnian-early Norian) and Neoaetosauroides (late Norian-Rhaetian), and it is nested as the sister-taxon of an unnamed clade, composed of Typothoracisinae and Desmatosuchinae, due to the absence of a ventral keel in the cervical vertebrae. Aetobarbakinoides presents a skeletal anatomy previously unknown among South American aetosaurs, with the combination of presacral vertebrae with hyposphene, anteroposteriorly short and unkeeled cervical vertebrae, gracile limbs, and paramedian osteoderms with a weakly raised anterior bar. Aetobarbakinoides is among the oldest known aetosaurs together with Aetosauroides from Argentina and Brazil and Stagonolepis robertsoni from Scotland, indicating a widely distributed early record for the group. In addition, the recognition of a suite of derived features in Aetobarbakinoides, which is one of the oldest known aetosaurs, is in agreement with an older origin for the group, as it is expected by the extensive ghost lineages at the base of the main pseudosuchian clades.

First Symposium on the Evolution of Crocodyliforms

2012-01-13T12:42:00.000-05:00

It seems the special issue of the Zoological Journal of the Linnean Society, "1st Symposium on the Evolution of Crocodyliforms", has finally appeared online. It introduces several new species and focuses on the great diversity of the lineage in an attempt to remove the stigma of crocodiles being considered living fossils. You can read the issue and get the details by following the above link, but I will give you the highlights.

The volume presents six new species (five new genera), bringing the count for new crocs of 2011 up to 17. Pol & Powell describe Lorosuchus nodosus gen. et sp. nov., a basal mesoeucrocodylian (Sebecidae) from the Paleocene of Argentina. Two new notosuchians from the Upper Cretaceous of Brazil are described: Caryonosuchus pricei gen. et sp. nov. (Spageosauridae) (Kellner et al. a.) and Labidiosuchus amicum gen. et sp. nov. with its bizarre dentition (a symphyseal dental battery) (Kellner et al. b.). Andrade et al present Goniopholis kiplingi sp. nov. (Lower Cretaceous, England) with a review of the genus and an updated definition, restricting Goniopholis to the Upper Jurassic-Lower Cretaceous of Europe. Clark describes several partial skeletons of a basal crocodyliform (Shartegosuchidae) from the Late Jurassic of Colorado (USA), naming it Fruitachampsa callisoni ge. nov., sp. nov.. The last new croc of the issue is Pieraroiasuchus ormezzanoi gen. nov., sp. nov., based on two fully articulated individuals from the Cretaceous of Italy, belonging to the Hylaeochamsidae (Buscalioni et al).

The volume also includes discussions of existing taxa, some with descriptions of new specimens. Riff et al look at the features of Stratiotosuchus maxhechti that support the view of baurusuchids as active terrestrial predators and their convergence with theropod dinosurs. The cranial anatomy of Baurusuchus albertoi is described and a phylogenetic analysis of baurusuchids is presented with the new data (Nascimento & Zaher). Moraes-Santos et al provide a brief report describing a new specimen of gavialoid from Brazil. Another review article examines abnormalities in the type specimen of Stratiotosuchus maxhechti revealing bone pathologies from two distinct injuries and insect boring marks (Cabral et al). Soto et al describe a new specimen of Uruguaysuchus aznarezi from the type locality. Brochu describes cranial fragments of Necrosuchus ionensis, revealing caimanine affinities, also providing a review of Paleocene-Eocene caiman biogeography. The issue includes a redescription of Meridiosaurus vallisparadisi with a phylogenetic analysis confirming the monophyly of Pholidosauridae, including a new definition (Fortier et al). Also, Figueiredo et al discuss a new specimen, comprised of postcranial remains, of Susisuchus anatoceps, revealing it as a basal neosuchian.

New Jersey Borealosuchus

2012-01-12T16:05:00.003-05:00

The first new croc of 2012 - Borealosuchus threeensis. Yes, that's three-ensis, so named because it was found near exit 3 of the New Jersey turnpike.

Christopher A. Brochu, David C. Parris, Barbara Smith Grandstaff, Robert K. Denton Jr. & William B. Gallagher. 2012. "A new species of Borealosuchus (Crocodyliformes, Eusuchia) from the Late Cretaceous–early Paleogene of New Jersey." Journal of Vertebrate Paleontology 32(1): 105-116 DOI:10.1080/02724634.2012.633585

Abstract

A lower jaw and associated postcranial remains from the Late Cretaceous–early Paleocene Hornerstown Formation of New Jersey form the basis of a new crocodyliform species, Borealosuchus threeensis. Although one of the oldest known species of Borealosuchus, phylogenetic analysis supports a closer relationship to Borealosuchus from the early Eocene than with other Late Cretaceous or early Paleocene forms. This is based on the shared presence of a short mandibular symphysis excluding the splenial, a small external mandibular fenestra, and ventral osteoderms composed of two sutured ossifications. It is also similar to Borealosuchus material from the Paleocene of western Texas, though conspecificity cannot be demonstrated at present. A close relationship with the basal alligatoroids Leidyosuchus or Diplocynodontinae is not supported. The distribution of lower jaws with very small slit-like external mandibular fenestrae, or no fenestrae at all, among basal crocodylian lineages (including Borealosuchus) and close crocodylian relatives suggests the fenestrae may have been ancestrally absent in Crocodylia and regained two or more times. Current phylogenetic hypotheses are consistent with dispersal of more-derived species of Borealosuchus to the Western Interior during the Paleocene, and they indicate the presence of several unsampled lineages crossing the Cretaceous-Paleogene boundary.

The Year In Crocs

2011-12-31T14:00:00.003-05:00

Each year, thanks to the hard work of a lot of great paleontologists, we get to add some new members to our favorite clade. In 2011, a total of 9 11 crurotarsans were named (and by this I mean they were named in a peer-reviewed paper with a publication date in 2011). Check out the list below:

Theriosuchus grandinaris - a Late Jurassic/Early Cretaceous neosuchian from Thailand - in Lauprasert, K., C. Laojumpon, W. Saenphala, G. Cuny, K. Thirakhupt, and V. Suteethorn. 2011. "Atoposaurid crocodyliforms from the Khorat Group of Thailand: first record of Theirosuchus from Southeast Asia." Paläontologische Zeitschrift 85(1): 37-47. DOI: 10.1007/s12542-010-0071-z

Decuriasuchus quartacolonia - a Triassic rauisuchian from Brazil - in Franca, M. A. G. and J. Ferigolo. 2011. 'Associated skeletons of a new middle Triassic "Rauisuchian" from Brazil' Naturwissenschaften 98 (5): 389-395 DOI: 10.1007/s00114-011-0782-3

Neptunidraco ammoniticus - a Jurassic metriorhynchid from Italy - in Cau, A. & F. Fanti. (2011) "The oldest known metriorhynchid crocodylian from the Middle Jurassic of North-eastern Italy, Neptunidraco ammoniticus gen. et sp. nov." Gondwana Research 19(2): 550-565. doi:10.1016/j.gr.2010.07.007

Andrea Cau, study co-author, posing with the counter top and a reconstruction of Neptunidraco (from Nat Geo)

Campinasuchus dinizi - a Cretaceous baurusuchid from Brazil - in Carvalho, I. D. S., V. D. P. A. Teixeira, M. L. D. F. Ferraz, L. C. B. Ribeiro, A. G. Martinelli, F. M. Neto, J. J. W. Seritch, G. C. Cunha, I. C. Cunha, and P. F. Ferraz. 2011. "Campinasuchus dinizi gen. et sp. nov., a new Late Cretaceous baurusuchid (Crocodyliformes) from the Bauru Basin, Brazil" Zootaxa 2871: 19-42 Open access online.

Life reconstruction (by Rodolfo Nogueira) of Campinasuchus dinizi from Carvalho et al 2011

Arenysuchus gascabadiolorum - a Cretaceous crocodyloid from Spain - in Puertolas, E., J. I. Canudo, P. Cruzado-Caballero. 2011. "A New Crocodylian from the Late Maastrichtian of Spain: Implications for the Initial Radiation of Crocodyloids." PLoS ONE 6(6) doi:10.1371/journal.pone.0020011

Pissarrachampsa sera -a Cretaceous baurusuchid fro Brazil - in Montefeltro, F. C., H. C. E. Larsson, and M. C. Langer. 2011. "A New Baurusuchid (Crocodyliformes, Mesoeucrocodylia) from the Late Cretaceous of Brazil and the Phylogeny of Baurusuchidae." PLoS ONE 6(7). doi:10.1371/journal.pone.0021916

From Figure 3 of Montefeltro et al 2011

Archerontisuchus guajiraensis -a Paleocene dyrosaurid from Colombia - in Hastings, A. K., J. I. Bloch, and C. A. Jaramillo. 2011. "A new longirostrine dyrosaurid (Crocodylomorpha, Mesoeucrocodylia) from the Paleocene of north-eastern Colombia: biogeographic and behavioural implications for New-World Dyrosauridae." Palaeontology, 54: 1095–1116. doi: 10.1111/j.1475-4983.2011.01092.x

Caipirasuchus paulistanus - a Cretaceous sphagesaurid from Brazil - in Fabiano V. Ioria and Ismar S. Carvalhoa. 2011. "Caipirasuchus paulistanus, a new sphagesaurid (Crocodylomorpha, Mesoeucrocodylia) from the Adamantina Formation (Upper Cretaceous, Turonian–Santonian), Bauru Basin, Brazil" Journal of Vertebrate Paleontology 31(6): 1255-1264 DOI:10.1080/02724634.2011.602777

Reconstruction of Caipirasuchus by D. Silva in Fabiano et al.

[Edit] I have been informed that there are three additional new crocs for this year. I overlooked them because they are named in a massive volume published by the Palaeontological Association, number 14 in their Field Guide to Fossils series. The contents of English Wealden Fossils are not available in any digital format, so reading about the new crocs requires purchasing the book. Fortunately, some brief comments are available over at Tetrapod Zoology.

Goniopholis willetti - an Early Cretaceous goniopholidid from England
Anteophthalmosuchus hooleyi - an Early Cretaceous goniopholidid from England
Leiokarinosuchus brookensis - an Early Cretaceous neosuchian from England

in Salisbury, S. W. & Naish, D. 2011. "Crocodilians." In Batten, D. J. (ed.) English Wealden Fossils. The Palaeontological Association (London), pp. 305-369

SVP 2011 Roundup - American Alligator Special Edition

2011-12-29T21:33:00.000-05:00

Oops! Looks like I forgot to post my summaries of the remaining 8 crurotarsan-themed abstracts from this year's SVP. In my defense though, several of them were focused on making inferences about dinosaurs, so my subconscious mind may have let things slip. Better late than never.

The American alligator (Alligator mississippiensis) seemed to be particularly popular this year, with a total of 8 abstracts dedicated to discussing aspects of the species' anatomy. Considering the alligator's availability for research and usefulness in studying extinct archosaurs, it's no surprise that these animals are such popular subjects for study.

Talks

"An intra-skeletal bone microanalysis of Alligator mississippiensis and its application to non-avian dinosaur osteohistology." Woodward, H.

Osteohistologic analysis of Alligator mississippiensis. Results:

each bone in an individual forms the same growth marks
femur, humerus, and tibiae have the highest growth rates
captive individuals show higher periodic growth than wild individuals = eco-phenotypic plasticity

Used results to infer aspects of ornithiscian dinosaur growth. Results:

basal ornithopods: rapid mineral deposition (tibia and femur) for only 2-3 growth cycles followed by slow deposition
Maiasaurus shows high growth rates throughout ontogeny

"Development of the lung in Alligator mississippiensis (Archosauria: Crocodylomorpha) and the evolution of the Archosaurian respiratory system." Schachner, E., Metzger, R., and Farmer, C. G.

description of the development of Alligator mississippiensis bronchi (and comparison with those of chickens)
investigation of the effects on oxygen tension morphogenesis during development
formation of bronchial chambers by branching morphogenesis with striking similarities in formation between alligators and birds
data suggest that lung development in extant archosaurs is determined by similar molecular and genetic programs

"Microstructure of the femoral growth plate in the American alligator: effects of growth rate, locomotor activity and circulatory pattern." Owerkowicz, T., Yang, J., Blank, J., Eme, J., and Hicks, J.

Are growth plates with a highly irregular border at the chondro-osseous junction a synapomorphy of dinosaur? Can growth plate thickness be used to determine skeletal growth rate?
Alligator growth plates show highly irregular chondro-osseous borders
Alligator growth plate height shows significant correlation with longitudinal growth rate
data suggest that growth plates are sensitive to systemic arterial oxygen tension and that an irregular chondro-osseous junction is an ancestral character of archosaurs
"propose a thicker growth plates appeared concurrently with the origin of in-series circulation, and may thus have set the stage for later acquisition of fast growth and endothermic metabolism in birds."

"Pelvic anatomy of Alligator mississippiensis and its significance for interpreting limb function in fossil archosaurs." Tsai, H., Holliday, C., and Ward, C.

test the hypothesis that accurately predicting in-vivo range of motion in the hip of the American alligator cannot be done using hard tissue manipulation alone
first description of American alligator acetabular anatomy
data show that the bone-only model enabled for more movement than the soft-tissue model
"this study provides new insight into soft tissue structures and their osteological correlations in the archosaur hip joint."

Posters

"Skeletochronology of the American alligator (Alligator mississippiensis): the utility of various elements for determining growth patterns and longevity." Garcia, B.

histological analysis of every bone type in American alligators
shows that, aside from long bones, elements like ribs and phalanges exhibit LAG deposition
developed a "map" of the alligator skeleton showing the best areas for finding unobstructed LAG deposition, helping determine which bones are best for analysis and where information is best preserved along those bones
information will allow researchers to make more informed sampling decisions given the destructive nature

"Variation in hindlimb muscle attachment sites in the American alligator (Alligator mississippiensis) and implications for paleobiological reconstructions." Taylor, E., Schachner, E., and Farmer, C.G.

examined hindlimb musculature in 19 specimens of Alligator mississippiensis
found high degrees of individual variation in most muscle attachments
suggests a need for caution when using osteological correlates in myological reconstruction

"Trigeminal nerve morphology in Alligator mississippiensis: implications for inferring sensory potential in extinct crocodyliforms." George, C.

cross-sectional study (histology, morphometrics, and 3D imaging) to identify patterns in neural and bony structures in Alligator mississippiensis and comparison with similarly-sized fossil crocodyliforms
"data suggest that trigeminal nerve morphology can be accurately inferred among living crocodilians."
extinct taxa:

Leidysuchus (eusuchian) and Phabdognathus (dyrosaur) have trigeminal ganglia similar to alligators
Hamadasuchus (peirosaur) had a much smaller ganglion (dome-pressure system not as well developed)

"these findings suggest that neural osteological correlates of the trigeminal system are informative features useful for investigation of crocodyliform as well as archosaur somatosensory evolution."

"Structure and function of a protosuchian mandibular symphysis using anatomical insights from Alligator mississippiensis." Skiljan, R., Gant, C., and Holliday, C.

comparison of the structure and function of the jaws (especially the mandibular symphysis) of protosuchians with Alligator mississippiensis
data suggest a transitional form of the symphysis is present in protosuchians, compared to the derived condition in crocodyliforms

Metriorhynchid Body Size

2011-11-26T21:05:00.000-05:00

Young, M. T., Bell, M. A., De Andrade, M. B. and Brusatte, S. L.. 2011. "Body size estimation and evolution in metriorhynchid crocodylomorphs: implications for species diversification and niche partitioning." Zoological Journal of the Linnean Society, 163: 1199–1216. doi: 10.1111/j.1096-3642.2011.00734.x

Abstract
Metriorhynchids were a peculiar group of fully marine Mesozoic crocodylomorphs, some of which reached large body size and were probably apex predators. The estimation of their total body length in the past has proven problematic. Rigorous size estimation was provided using five complete metriorhynchid specimens, by means of regression equations derived from basicranial and femoral length against total body length. The use of the Alligator femoral regression equation as a proxy to estimate metriorhynchid total body length led to a slight underestimation, whereas cranial regression equations of extant genera resulted in an overestimation of body length. Therefore, the scaling of crania and femora to total body length of metriorhynchids is noticeably different from that of extant crocodylians, indicating that extant crocodylians are not ideal proxies for size reconstruction of extinct taxa that deviate from their semi-aquatic morphotype. The lack of a correlation between maximum, minimum, or the range of generic body lengths with species richness demonstrates that species diversification is driven by factors other than just variation in body size. Maximum likelihood modelling also found no evidence for directionality in body size evolution. However, niche partitioning in Metriorhynchidae is mediated not only by craniodental differentiation, as shown by previous studies, but also by body size variation.

Reassessment of Some Middle Triassic Rauisuchians

2011-11-26T20:52:00.000-05:00

Stephan Lautenschlager and Julia Brenda Desojo. 2011. "Reassessment of the Middle Triassic rauisuchian archosaurs Ticinosuchus ferox and Stagonosuchus nyassicus." Paläontologische Zeitschrift 85 (4): 357-381, DOI: 10.1007/s12542-011-0105-1

Abstract
The Middle Triassic (Anisian) rauisuchian archosaurs Ticinosuchus ferox and Stagonosuchus nyassicus are two of the earliest representatives of this group and therefore of special importance for our understanding of the evolution and early diversification of Rauisuchia. Both taxa are well preserved and, in the case of the holotype of Ticinosuchus ferox, nearly complete and articulated. However, the original descriptions and recent revisions of the material do not sufficiently cover all aspects of their osteology. We identify new skull elements previously unknown for Ticinosuchus ferox and present new reconstructions of the pectoral and pelvic girdle elements. Vertebral laminae and fossae are described for the first time in both Ticinosuchus ferox and Stagonosuchus nyassicus. Newly recognised character states of Stagonosuchus nyassicus include the presence of additional infraprezygapophyseal and infrapostzygapophyseal laminae in the cervical vertebrae, a hyposphene-hypantrum articulation in the dorsal vertebrae and a fibula with a posteromedial depression. Furthermore, we provide a revised and emended diagnosis for both taxa, including several autapomorphies for Stagonosuchus nyassicus (e.g. a boss-like protuberance on the postacetabular process of the iliac blade and a marked short dorsolateral crest on the proximal ischium). We review the taxonomic status of a further specimen of Ticinosuchus ferox, as well as material related to Stagonosuchus nyassicus from the Manda Beds of Tanzania. Additionally, we discuss the distribution and possible function of rauisuchian characters, such as accessory neural spines in the caudal vertebrae, in these and other rauisuchian taxa.

Pelvic and Hindlimb Myology in Poposaurus

2011-11-26T20:36:00.000-05:00

Emma R. Schachner, Phillip L. Manning, and Peter Dodson. 2011. "Pelvic and hindlimb myology of the basal archosaur Poposaurus gracilis (archosauria: Poposauroidea)" Journal of Morphology 272 (12): 1464–1491 DOI: 10.1002/jmor.10997

Abstract
The discovery of a largely complete and well preserved specimen of Poposaurus gracilis has provided the opportunity to generate the first phylogenetically based reconstruction of pelvic and hindlimb musculature of an extinct nondinosaurian archosaur. As in dinosaurs, multiple lineages of basal archosaurs convergently evolved parasagittally erect limbs. However, in contrast to the laterally projecting acetabulum, or “buttress erect” hip morphology of ornithodirans, basal archosaurs evolved a very different, ventrally projecting acetabulum, or “pillar erect” hip. Reconstruction of the pelvic and hindlimb musculotendinous system in a bipedal suchian archosaur clarifies how the anatomical transformations associated with the evolution of bipedalism in basal archosaurs differed from that of bipedal dinosaurs and birds. This reconstruction is based on the direct examination of the osteology and myology of phylogenetically relevant extant taxa in conjunction with osteological correlates from the skeleton of P. gracilis. This data set includes a series of inferences (presence/absence of a structure, number of components, and origin/insertion sites) regarding 26 individual muscles or muscle groups, three pelvic ligaments, and two connective tissue structures in the pelvis, hindlimb, and pes of P. gracilis. These data provide a foundation for subsequent examination of variation in myological orientation and function based on pelvic and hindlimb morphology, across the basal archosaur lineage leading to extant crocodilians.

SVP 2011 Roundup - Crocodylomorph Edition Part 3

2011-11-20T13:32:00.000-05:00

Crocodylomorph Morphology and Systematics

(in order of presentation)

Talks

"Comparative morphometrics and phylogenetic perspectives on the morphospace of the crocodyliform skull." Wilberg, E.

presents a quantitative approach for assessing skull shape in Crocodyliformes (helping to avoid subjective intermediate assignments)
compared multiple methodologies for comparing skull shape

2D geometric morphometrics (homologous landmarks and sliding semi-landmarks) - results suggest 3 or 8 shape categories
Eliptical Fourier Analysis (EFA) of skull outlines - results suggest 3 shape categories

overall skull shape should not be used as a discrete character in phylogenetic analyses, but can help in evaluating ecological and functional trends within claes

"Evolution of the otic region of fossil Crocodyliformes." Montefeltro, F. and Larsson, H.

terrestrial taxa - large, more vertical otic apertures and recess, relatively large tympanic membranes

notosuchians show the most extreme expansion of the otic region and well developed scar for the attachment of the tympanic membrane = very good hearing

semi aquatic and aquatic taxa - reduced otic apertures and tympanic membranes

extreme reductions in Metriorhynchidae = hearing may have been insignificant

quadrate fenestra may have played a role in hearing

Posters
"Crocodyliform aquatic locomotion and axial flexibility: comparative vertebral anatomy of mesoeucrocodylians." Felice, R. and O'Connor, P.

quantified vertebral metrics to evaluate whether crocodylians possess specialized skeletal morphology associated with a semi-aquatic lifestyle
terrestrial taxa - dorsal centra are about as wide as they are tall
semi-aquatic taxa - dorsal centra are wider than tall

"Jaw mechanics of crocodiles reveal their fast mastication." Suzuki, D., Hayashi, S., Chiba, K., and Tanaka, K.

observed movement of the cartilago transiliens (CT) in the musculus pterygoideus anterior (MPA) in extant crocs using CAT scans
the CT retains a rough surface on the lateral wing of the pterygoid, making it useful for studying fossil taxa
MPA moves the CT anteriorly = rapid jaw closure

"Phylogenetic patterns, homoplasy, and the evolution of the antorbital fenestra in Crocodyliformes." Leardi, J., Pol, D., and Fernandez, M.

phylogenetic analysis to evaluate the pattern of character evolution of the antorbital fenestra
closure of the antorbital fenestra occurred independently up to 8 times within Crocodyliformes (mostly in Mesoeucrocodylia)
antorbital fenestra independently reappears in some notosuchians (possibly in basal thalattosuchians)
suggests that the antorbital fenestra in Crocodyliformes is extremely homoplastic

"Fleshing out the neosuchian tree: a reevaluation of the crocodyliform Shamosuchus from the Cretaceous of Asia." Turner, A. and Brochu, C.

Shamosuchus is important in understanding the character changes occurring at the origin of Eusuchia
reevaluation of Shamosuchus species reveals only three valid species: S. djadochtaensis, S. gradilifrons, and S. ancestralis
results suggest a diverse Shamosuchus clade in the Cretaceous of eastern Asia

"Cranial anatomy and osteology of Gavialis gangeticus using computerized axial tomography: implications for gavialoid phylogeny." Gold, M.

ontogenetic changes in gharials are likely obscuring data
description of the cranial anatomy of a hatchling G. gangeticus based on CT data
reveals numerous ontogenetic of the skull and braincase
morphological data seem to support the molecular data, that certain plesiomorphiuc states in are secondarily reversed

"A geometric morphometric analysis of Crocodylus niloticus: osteological evidence for a cryptic species complex." Nestler, J.

geometric morphometric analysis of the variation in the skull of C. niloticus
variation in population in broadly based on river basins
at least 3 distinct populations within the species with at least 2 being more distinct from each other than from other members of the species (and at least one may be endangered) = cryptic species complex, supporting molecular data from previous studies
paleontology can inform on conservation and issues of diversity

"The evolution of exoskeletal ossifications in notosuchian crocodyliformes." Hill, R. and O'Connor, P.

most notosuchians show a general trend toward the reduction of dorsal osteoderms along with the expansion of the caudal osteoderm shield
general trend towards the reduction of surface ornamentation in favor of increased internalization
Pakasuchua - most extreme reduction of osteoderms; robust articulating shield of osteoderms surrounding the tail; reduced osteoderms around the dorsosacral transition; presence of ossified tendons (first reported in Crocodyliformes)
osteoderm reduction trend in notosuchians may be associated with decreased body size and terrestrial habitat

Form and Function in the Metriorhychid Skull

2011-11-17T17:46:00.000-05:00

Mark T. Young, Mark A. Bell and Stephen L. Brusatte. 2011. "Craniofacial form and function in Metriorhynchidae (Crocodylomorpha: Thalattosuchia): modelling phenotypic evolution with maximum-likelihood method." Biology Letters 7(6): 913-916 DOI: 10.1098/rsbl.2011.0357

Abstract

Metriorhynchid crocodylomorphs were the only group of archosaurs to fully adapt to a pelagic lifestyle. During the Jurassic and Early Cretaceous, this group diversified into a variety of ecological and morphological types, from large super-predators with a broad short snout and serrated teeth to specialized piscivores/teuthophages with an elongate tubular snout and uncarinated teeth. Here, we use an integrated repertoire of geometric morphometric (form), biomechanical finite-element analysis (FEA; function) and phylogenetic data to examine the nature of craniofacial evolution in this clade. FEA stress values significantly correlate with morphometric values representing skull length and breadth, indicating that form and function are associated. Maximum-likelihood methods, which assess which of several models of evolution best explain the distribution of form and function data on a phylogenetic tree, show that the two major metriorhynchid subclades underwent different evolutionary modes. In geosaurines, both form and function are best explained as evolving under ‘random’ Brownian motion, whereas in metriorhynchines, the form metrics are best explained as evolving under stasis and the function metric as undergoing a directional change (towards most efficient low-stress piscivory). This suggests that the two subclades were under different selection pressures, and that metriorhynchines with similar skull shape were driven to become functionally divergent.

SVP 2011 Roundup - Crocodylomorph Edition Part 2

2011-11-16T13:32:00.000-05:00

New Crocodylomorph Species and Specimens

(in order of presentation)

Talks

" A new basal crocodylomorph from the Late Jurassic of Patagonia and its implications for the evolution of the crocodyloform braincase." Pol, D., Rauhut, O., Lecuona, A., and Leardi, J.

Late Jurassic Canadon Caleareo Formation, Patagonia
posterior region of the skull, fragmentary remains of the rostrum, palate, mandible, and postcranium
unique combination of autapomorphies, crocodylomorph plesiomorphies, and crocodyliform apomorphies
taxa found to be the closest to (just outside of) Crocodyliformes, closer than Junggarsuchus
suggests that the braincase articulation with the palate and quadrate occured before Crocodyliformes

"A new eusuchian crocodyliform with novel cranial integument and the origin of Crocodylia." Holiday, C. and Gardner, N.

found in the coastal deposits of the Early Late Cretaceous Kem Kem Beds, Morocco
cranial remains - long, flat skull, possibly over 2 meters
novel integumentary display structure (possible thermoregulatory function as well)
new taxon found to be a derived eusuchian and the sister taxon to crown Crocodylia
earliest eusuchian from Africa - biogeographic implications for the origin of modern crocodylians (circum-Tethys vs. North America)

"New remains of Miadanasuchus oblita from the Late Cretaceous of Madagascar and a reevaluation of Trematochampsidae." Sertich, J.

Upper Cretaceous Maevarano Formation, Madagascar
well preserved partial skull, numerous isolated cranial and postcranial elements, allowing for a comprehensive assessment of morphology
Miadanasuchus compares closely with other trematochampsids
a reevaluation of Trematochampsidae and Peirosauridae shows that there are 12 valid genera within a monophyletic Trematochamsidae and that Peirosauridae is synonymous with Trematochampsia. Trematochamsidae was found to be closely related to Mahajangasuchidae and Araripesuchus.

"New primitive caimanine (Crocodylia, Alligatoridae) from the Miocene of Panama." Hastings, A., Bloch, J., Rincon, A., MacFadden, B., and Jaramillo, C.

Culebra Formation, early Miocene, Panama
complete skull of a new taxon
found to be just outside of Caimaninae
important biogeographic implications, suggesting that caimans originated in the New World Tropics, entered North and South America in the Paleogene and persisted in the tropics into the Miocene after disappearing from higher latitudes

Posters

"A new specimen of Araripesuchus (Mesoeucrocodylia) with soft tissue preservation from the Lower Cretaceous Romualdo Formation (Araripe Basin), Brazil." Figueiredo, R. and Kellner, A.

nearly complete skeleton (skull, limbs, vertebral column, 2 rows of osteoderms)
the orbit size and proportions are consistent with A. gomesii while the long, slender limbs are consistent with A. gomesii, A. wegeneri, and A. tsangatsangana
significant soft tissue preservation (white substance, likely phosphatized) consisting mostly of muscle fibers but also epidermis

"A new crocodyliform from the middle Cretaceous Woodbine Formation of Texas." Allen, E., Main, D., and Noto, C.

Arlington Archosaur Site of the Woodbine Formation (delta plain deposits)
disarticulated partial skull and significant postcranial material of one individual along with disarticulated material of several other individuals
about 5 meters long, short dentary symphysis, paired dentary pseudocanines, and a robust triangular snout
new taxon is a mesoeucrocodylian, possibly a basal goniopholidid or thalattosuchian

"A new, small-bodied alligatoroid from the Hell Creek Formation (Late Maastrichtian) of Montana." Householder, M., Williams, S., and Tremaine, K.

small-bodied (about 1 meter), mature or nearly mature individual (based on fused neurocentral sutures)
bears some similarities to Brachychampsa montana and other small-bodied alligatoroids, but is a distinct taxon
represents the southern-most occurrence of a small-bodied alligatoroid within the Western Interior Basin during the Late Cretaceous

"The palate and braincase in goniopholidid crocodyliforms: insights from a new skull of Eutretauranosuchus delfsi." Pritchard, A. and Turner, A.

well-preserved, complete skull with CT scans revealing the palate and braincase
dorsoventral crushing distorted some braincase elements, although the anatomical positions are preserved
incorperation of the new skull data into a phylogenetic analysis unites Amphicotylus, Calsoyasuchus, Eutrerauranosuchus, and Sunosuchus into a clade of derived goniopholidids, all sharing a unique palatal morphology

SVP 2011 Roundup - Crocodylomorph Edition Part 1

2011-11-14T11:42:00.000-05:00

General Crocodylomorph Ecology and Evolution

(in order of presentation)

Talks

"Campanian crocodyliforms of Laramidia: new insights from the Kaiparowits Basin of southern Utah." Irmis, R., Sertich, J., Hutchison, J. H., And Titus, A.

comprehensive survey of Kaiparowits crocodyliforms

large, goniopholidid-like mesoeucroc.
basal alligatorids: Deinosuchus hatcheri and Brachychampsa
small alligatoroid lacking globidont teeth

clear biogeographic relationship with the San Juan Basin (New Mexico) - some regionality but also endemic taxa
supports the hypothesis of a distinct southern biogeographic province

"Direct evidence of crocodyliform predation on small dinosaurians from the Kaiparowits Formation of Utah." Drumheller, S. and Boyd, C.

predation by a small crocodyliform on a juvenile basal ornithopod (new Hypsolophodont)

several bite marks characteristic of crocs
partial tooth embeded in femur (distal tip had been broken off previously)

"The myth of the living fossil: basal crown group relationships, reversing polarities, and restoration of the ancestral crocodylian." Brochu, C., Turner, A., Allen, E., and Wilberg, E.

outgroups of Crocodylia predominantly small bodied (less than 2 meters)
the crocodylian ancestral condition was likely equivalent to the small durophagous alligatorines of the Paleogene
living crocodylians are not generalized but independently highly specialized (NOT LIVING FOSSILS!!!!)

Posters

"Freshwater niche competition between choristoderes and crocodiles in the Mesozoic and Paleogene." Matsumoto, R.

Early Cretaceous of Asia - high diversity of choristoderes, no aquatic crocs
Middle Jurassic thru Eocene of Europe - only small lizard-like choristoderes, co-occuring with larger crocs
Cretaceous thru Paleogene of Euramerica - neochoristoderes co-occur with similar sized crocs, but neochoristoderes are the only strongly longirostrine reptiles
long-snouted crocs diversify in freshwater after the extinction of neochoristoderes (Oligo-Miocene)

"Late Neogene Alligator evolution and a description of specimens from the Gray Fossil Site, southern appalachians, USA." Schubert, B., Mead, J., and Stout, J.

abundant Alligator material

osteroderms and other fragmentary material
mostly complete juvenile
pathological adult skull
two adult partial post-cranial skeletons

Alligator of Gray Fossil Site posses a mixture of characters found in A. olseni, A. mefferdi, and A. mississippiensis

"Crocs not theropods were likely top predators on the Cretaceous dinosaur freeway: implications of a large track census." Lockley, M. and Lucas, S.

at least 1380 individual trackmakers
mostly ornithopods (71%)
only small theropods present (not large enough to prey on ornithopods)
abundant crocodylian tracks (walking and swimming), including large individual (around 4 meters)

"A taphonomic and paleoecological comparison of isolated crocodyliform teeth from the Woodbine Formation of Texas and the Hell Creek Formation of Montana." Bennett, G., Main, D., Peterson, R., and Anderson, B.

4 different crocodyliforms in the Woodbine Formations, including Woodbinesuchus and a new genus
2 different crocodyliforms in the Hell Creek (Brachychampsa montana and Borealosuchus sternbergi), showing similar population structure to A. mississippiensis.

SVP 2011 Roundup - Triassic Crurotarsan/Pseudosuchian Edition

2011-11-09T16:50:00.000-05:00

Talks

"A new archosaur (Diapsida: Archosauriformes) from the marine Triassic of China." Wu, X., Li, C., Zhao, L., Sato, T., and Wang, L.

a new, nearly complete (except for some of the tail) crurotarsan archosaur from the Falanf Formation (Middle Triassic - Ladinian) of China

likely a basal poposauroid (sensu Nesbitt 2011), about 1.5 meters in length

snout more than twice the length of the rest of the skull (about 24 cm total)
although found in marine sediments, it has few anatomical modifications toward an aquatic lifestyle but still not likely fully terrestrial (fish gut contents, posteriorly positioned external naris)
sister-group relationship with Qianosuchus (only other Middle Triassic archosaur found in marine sediments of China), but with a poor bootstrap value

"An enigmatic archosauriform from the Manda Beds (Middle Triassic) of Southwestern Tanzania: character conflict at the base of Pseudosuchia." Nesbitt, S., Sidor, C., Angielczyk, K., Smith, R., and Tsuji, L.

a new archosaur with an unusual mix of character states
basal pseudosuchian, closely related to/ just outside of Paracrocodylomorpha
new data produces little change in relationships but a drastic change in character optimization (overall data is still obscured by high rates of homoplasy and incomplete specimens)
shows that the plesiomorphic bauplan of archosaurs was likely "rauisuchian"

Posters

"Comparative paleohistology of Triassic rauisuchian and aetosaurian osteoderms (Archosauria:Pseudosuchia)." Scheyer, T., Desojo, J., and Cerda, I.

sampled 8 rauisuchian, 10 aetosaurs, and Revueltosaurus
rauisuchians had compact bone, showed high growth rates early, and reduced growth rates later in development
in aetosaurs, a few taxa showed rapid growth, but most showed slow growth (parallel-fibered/ lamellar-zonal bone)
Revueltosaurus showed mostly densely remodeled parallel-fibered bone

"A newly recognized specimen of the phytosaur Redondasaurus from the Upper Triassic Owl Rock Member (Chinle Formation) and its biostratigraphic implications." Parker, W., Martz, J., and Dubiel, R.

a phytosaur specimen from the Owl Rock Member (Chinle Fm) has been identified as Redondasaurus, not Pseudopalatus
this puts mush of the Owl Rock in the Apachean Biozone, drastically changing biostratigraphic correlations of the upper Chinle and Dockum
shows that there is no basis for the Tr-5 unconformity (no faunal turnover or depositional hiatus)

"The relationships and type locality of Heptasuchus clarki, Chugwater Group (Middle to Upper Triassic), Southeastern Big Horn Mountains, Wyoming, USA." Zawiskie, J., Dawley, R., and Nesbitt, S.

type locality is poorly constrained, but likely equivalent to the Popo Agie Formation
Heptasuchus is the sister taxon to Batrachotomus
minimum of four Heptasuchus individuals at the type locality, further suggesting that loricatans may have lived in groups (like Decuriasuchus)

"The trackmaker of the Late Triassic tetrapod footprint ichnotaxon Brachyirotherium was an aetosaur." Lucas, S., Heckert, A., and Lockley, M.

aetosaurs have the appropriate manus/pes morphology, were capable of a nearly over-stepped stride, and have the appropriate geographic/stratigraphic distribution to be consistent with Brachyirotherium
rauisuchians and spenosuchians excluded by manus/pes morphology

"Diversity of aetosaurs (Archosauria: Stagonolepidae) in the Upper Triassic Pekin Formation (Deep River Basin), North Carolina." Schneider, V., Heckert, A., and Fraser, N.

new specimen of a partial aetosaur carapace, composed of the first ten rows of osteoderms (including a full, articulated row of cervicals)
shows character states of both Longasuchus and Lucasuchus
at least three genera of aetosaur in the Pekin Formation (Lucasuchus, Coahomasuchus, and whichever genus is represented by the new specimen), correlating it with the lower Dockum Group

"A virtual phytosaur (Archosauria: Crurotarsi) endocast and its implications for sensory system evolution in archosaurs." Holloway, W. and O'Keefe, R.

cranial endocast (CT scan) of a complete Smilosuchus adamanensis skull
endocranial morphology very similar to Crocodylus johnstoni except for enlarged pineal body in Smilosuchus
"This highly conserved cranial endocast morphology is consistent throughout Crurotarsi, regardless of overall body morphology or ecology, with a trend of pineal body size reduction from the enlarged basal condition to a reduced crown condition." (quoted from the abstract)

A New Upper Cretaceous Sphagesaurid

2011-11-08T15:53:00.000-05:00

Fabiano V. Ioria and Ismar S. Carvalhoa. 2011. "Caipirasuchus paulistanus, a new sphagesaurid (Crocodylomorpha, Mesoeucrocodylia) from the Adamantina Formation (Upper Cretaceous, Turonian–Santonian), Bauru Basin, Brazil" Journal of Vertebrate Paleontology 31(6): 1255-1264 - (Online November 8th) DOI:10.1080/02724634.2011.602777

Abstract
A skull and mandible of a new species of notosuchian, Caipirasuchus paulistanus, belonging to the Sphagesauridae, were discovered in the rocks of the Adamantina Formation (Bauru Basin: Late Cretaceous). The main autapomorphies are external naris bordered only by premaxillae; very high pterygoids and ectopterygoids; palatines contacting maxillae by a cuneiform process; well-developed oval antorbital fenestra; premaxilla with four teeth; dentary with ten teeth and two diastemata; and one diastema in the premaxilla and another between the fourth alveolus of the premaxilla and the first of the maxilla. Morphological analysis and experimental data suggest an animal with a powerful bite and a dentition with specific regions of action, one adapted to apprehension and the other to food processing.

Osteohistology of Triassic Archosauromorphs

2011-11-08T15:48:00.000-05:00

Jennifer Botha-Brink and Roger M. H. Smith. 2011. "Osteohistology of the Triassic archosauromorphs Prolacerta, Proterosuchus, Euparkeria, and Erythrosuchus from the Karoo Basin of South Africa." Journal of Vertebrate Paleontology 31(6): 1238-1254 - (Online November 8th) DOI:10.1080/02724634.2011.621797

Abstract
The South African non-archosauriform archosauromorph Prolacerta and the archosauriforms Proterosuchus, Erythrosuchus, and Euparkeria were important constituents of the Early to early Middle Triassic Karoo ecosystem following the end-Permian mass extinction. We present new data on the osteohistology of these stem archosaurs and provide insight into their paleobiology. Bone tissues of the Early Triassic Prolacerta contain a poorly defined fibro-lamellar complex, with parallel-fibered bone in some regions, whereas the contemporaneous Proterosuchus exhibits rapidly forming uninterrupted fibro-lamellar bone early in its ontogeny, which becomes slow forming lamellar-zonal bone with increasing age. The early Middle Triassic Erythrosuchus deposited highly vascularized, uninterrupted fibro-lamellar bone throughout ontogeny, whereas the growth of the contemporaneous Euparkeria was relatively slow and cyclical. When our data are combined with those of previous studies, preliminary results reveal that Early and Middle Triassic non-crown group archosauromorphs generally exhibit faster growth rates than many of those of the Late Triassic. Early rapid growth and rapid attainment of sexual maturity are consistent with life history expectations for taxa living in the unpredictable conditions following the end-Permian mass extinction. Further research with larger sample sizes will be required to determine the nature of the environmental pressures on these basal archosaurs.

SVP 2011 Roundup - Archosauromorph Edition

2011-11-08T14:38:00.000-05:00

Archosauromorphs and General Archosaur Evolution

(in order of presentation)

Talks

"Archosauromorph bone histology reveals early evolution of elevated growth and metabolic rates." Werning, S., Irmis, R., Smith, N., Turner, A., and Padian, K.

extant and extinct ornithodirans show high metabolic rates, but not extant crocodylians
study of evolution of growth rate in archosauromorphs through an expanded histological database and using much more rigorous methods for collecting data
characters associated with high metabolic rates appear in a short, stepwise accumulation along the archosauriform tree
a reversal likely occured along the pseudosuchian line

Aetosaurs and relatives show early rapid growth, but slow growth later on
Shuvosaurs show fast growth throughout life

"Postcranial skeletal pneumaticity and the evolution of archosaur respiratory systems." Barrett, P., Butler, R., Gower, D., and Abel, R.

unidirectional airflow present in extant archosaurs
soft tissue associated with unidirectional airflow/ postcranial skeletal pneumaticity (PSP) not preserved by fossil record but fossae, foramina, and laminae are preserved
pseudosuchians (phytosaurs, aetosaurs, poposaurs) posses many vertebral laminae and fossae, but no internal features
no conclusive evidence in extinct archosaurs other than saurischians and pterosaurs but still likely that they had less well-developed avian-like respiratory systems with non-invasive air sacs and unidirectional air flow

"Phylogenetic congruence between cranial and postcranial characters in archosaur systematics." Mounce, R. and Wills, M.

showed a significant incongruence of cranial and postcranial signals (cranial characters appear to be significantly less homoplastic)
results may indicate different evolutionary rates between cranial and postcranial characters

"Osteohistology of Triassic archosauromorphs from the Karoo Basin of South Africa." Botha-Brink, J. and Smith, R.

looked at Prolacerta, Proterosuchus, Erythrosuchus, and Euparkeria
Early/Middle Triassic archosauromorphs (non-crown group) show fast growth early in their life
early rapid growth and early onset of sexual maturity are consistent with the life history expected from harsh, unpredictable conditions after the Permian/Triassic extinction

"New information on the Triassic vertebrate faunas of Antarctica." Sidor, C., Smith, R., Huttenlocker, A., Peecook, B., and Hammer, W.

small Prolacerta-like archosauromorph found under a Lystrosaurus and a Proterosuchus-like archosauriform
vertebrates of the lower Fremouw Formation likely correspond to the post-extinction recovery fauna of South Africa (Karoo Basin)
faunas of the two continents differentiate in the Middle Triassic
using network science for faunal analysis

"Uniting microevolution and macroevolution in deep time: the zone of variability in Archosauromorpha." Bhullar, B., Bever, G., Merck, J., Lyson, T. and Gauthier, J.

a phylogenetic "zone of variability" (ZOV) occurs before apomorphies become fixed
detected indirectly - stem members of a clade show lots of variability in character states before they become fixed in crown group members

derived archosauriforms show an absence of a parietal foramen, an absence of supratemporals, and a complete lower temporal bar
stem archosauriforms show a ZOV of these characters

detected directly - in a single taxon, variation in such character states occur between individuals

in Prolacerta broomi, the three characters listed above in derived archosaurs are variably present and absent (in almost all permutations) in fossil individuals

Posters

"Anatomy and affinities of large archosauromorphs from the lower Fremouw Formation (Early Triassic) of Antarctica." Crandall, J., Hellert, S., Smith, N., Hammer, W., and Makovicky, P.

first evidence of Archosauriformes in the Early Triassic of Antarctica
found a partial presacral vert and distal end of the left humerus of a large archosauriform from just after the P/Tr

large size is contra the "lilliput effect" of mass extinctions

"New data on the archosaur fauna of the Middle Triassic (Anisian) Ntawere Formation of Zambia." Peecook, B., Sidor, C., Nesbitt, S., Angielczyk, K., and Steyer, S.

first diagnostic remains of archosaurs from the Ntawere Formation - teeth, large pseudosuchian vertebra, pelvic and vertebral material of a silesaurid
Ntawere Formation (and Manda beds) shows a higher diversity of archosaurs than the ealier Karoo Basin

SVP 2011 - A Quick Summary

2011-11-08T11:52:00.000-05:00

For those of you who missed this year's meeting of the Society of Vertebrate Paleontology, don't feel too bad. There were plenty of good talks this year, but also a fair share of disappointments.

I'll start with what was good about this meeting. At the business meeting, it was announced that of all the abstracts submitted on archosaurs, the dinosaurs were far outweighed by the non-dinosaurs - good news for those of us who are fans of the "forgotten archosaurs". I will be following this post with several summarizing the information presented on archosauromorphs, Triassic pseudosuchians/crurotarsans, and crocodylomorphs. The exhibitors this year had some good items for croc fans, including a life-size Sarchosuchus skull (Bone Clones, Inc) and prints of the mural from the Petrified Forest Rainbow Forest Museum (Paleovista), featuring the Adamanian (Triassic) fauna of the Chinle Formation (including Smilosuchus, Postosuchus, Desmatosuchus, and many others).

This year's meeting was somewhat disappointing due to a complete lack of food and the choice of venue. Las Vegas (especially a casino) is one of the last places I think of when I hear "academic/professional conference". Most of the people I spoke to felt sick all week, but no one could tell if they had a cold or if it was just the dry, cigarette smoke-filled air that was making them feel crummy.

I think we can all agree that we're looking forward to next year's meeting in Raleigh (there's a phytosaur on the logo!).

Happy Halloween!

2011-10-31T21:57:00.000-04:00

Happy Halloween Everyone! This year, I decided to carve my pumpkin as Smilosuchus. I got a lot of compliments from trick-or-treeters, although a lot thought it was a dinosaur. A few managed to guess it was a crocodile, which I figured was close enough for 8-year-olds. Did anyone else carve paleo-inspired pumpkins?

Alright, I'm off to Vegas. See you all at SVP!

SVP 71st Annual Meeting

2011-10-26T16:59:00.000-04:00

The annual meeting of the Society of Vertebrate Paleontology is just one week away. Incorporated into the logo for this year's meeting is the Nevada state fossil, Shonisaurus popularis, a Late Triassic ichthyosaur, as well as the dinosaur track Eubrontes (the suit on the cards).

There will be no shortage of talks and posters on "forgotten archosaurs" at this years meeting. On Wednesday, there will be a handful of general archosaur talks in the morning and afternoon. Thursday talks will be sparse, but there will be dozens of good posters. All day Friday and Saturday morning are almost completely devoid of non-dinosaurian archosaur talks, but Saturday afternoon will bring us the croc talks. Not a bad way to end the meeting.

A message from the Student & Post-Doctoral Liaison Committee

As a member of the committee, I have a small request to ask of my lovely readers: PLEASE BRING LOTS OF REPRINTS! Each year, the S&PLC hosts the Student Roundtable Forum and Reprint Exchange. We rely entirely on generous donations from SVP members for reprints so, if you have a bunch of reprints sitting around your office and wouldn't mind contributing, please bring them to the meeting. You can bring them to the S&PLC table, where we will be selling raffle tickets and offering guidance to first time attendees.

Each year, the student committee sells raffle tickets for a chance to win a free student membership or fabulous door prizes. Not a student? You can still buy a raffle ticket (or 20) and donate it to a student. Proceeds benefit the SVP Education and Research Fund. More info can be found at the annual meeting website.

The Sail-Backed Poposauroid - Ctenosauriscus

2011-10-16T17:32:00.000-04:00

Butler RJ, Brusatte SL, Reich M, Nesbitt SJ, Schoch RR, et al. 2011. "The Sail-Backed Reptile Ctenosauriscus from the Latest Early Triassic of Germany and the Timing and Biogeography of the Early Archosaur Radiation." PLoS ONE 6(10): e25693. doi:10.1371/journal.pone.0025693

Abstract

Background
Archosaurs (birds, crocodilians and their extinct relatives including dinosaurs) dominated Mesozoic continental ecosystems from the Late Triassic onwards, and still form a major component of modern ecosystems (>10,000 species). The earliest diverse archosaur faunal assemblages are known from the Middle Triassic (c. 244 Ma), implying that the archosaur radiation began in the Early Triassic (252.3–247.2 Ma). Understanding of this radiation is currently limited by the poor early fossil record of the group in terms of skeletal remains.

Methodology/Principal Findings
We redescribe the anatomy and stratigraphic position of the type specimen of Ctenosauriscus koeneni (Huene), a sail-backed reptile from the Early Triassic (late Olenekian) Solling Formation of northern Germany that potentially represents the oldest known archosaur. We critically discuss previous biomechanical work on the ‘sail’ of Ctenosauriscus, which is formed by a series of elongated neural spines. In addition, we describe Ctenosauriscus-like postcranial material from the earliest Middle Triassic (early Anisian) Röt Formation of Waldhaus, southwestern Germany. Finally, we review the spatial and temporal distribution of the earliest archosaur fossils and their implications for understanding the dynamics of the archosaur radiation.

Conclusions/Significance
Comprehensive numerical phylogenetic analyses demonstrate that both Ctenosauriscus and the Waldhaus taxon are members of a monophyletic grouping of poposauroid archosaurs, Ctenosauriscidae, characterised by greatly elongated neural spines in the posterior cervical to anterior caudal vertebrae. The earliest archosaurs, including Ctenosauriscus, appear in the body fossil record just prior to the Olenekian/Anisian boundary (c. 248 Ma), less than 5 million years after the Permian–Triassic mass extinction. These earliest archosaur assemblages are dominated by ctenosauriscids, which were broadly distributed across northern Pangea and which appear to have been the first global radiation of archosaurs.

Rauisuchian Osteoderms

2011-09-29T13:31:00.001-04:00

Scheyer, T. M. and J. B. Desojo. 2011. "Palaeohistology and external microanatomy of rauisuchian osteoderms (Archosauria: Pseudosuchia)." Palaeontology. DOI: 10.1111/j.1475-4983.2011.01098.x

Abstract

The presence of postcranial dermal armour is plesiomorphic for Archosauria. Here, we survey the external microanatomy and histology of postcranial osteoderms (i.e. dorsal paramedian and caudal osteoderms) of rauisuchians, a widely distributed assemblage of extinct predatory pseudosuchians from the Triassic. The osteoderms of eight rauisuchian taxa were found to be rather compact bones, which usually lack significant bone remodelling or large areas of cancellous bone. The presence of highly vascularized woven or fibrolamellar bone tissue deposited in the core areas indicates higher growth rates during earlier life stages, whereas a more compact parallel-fibred bone matrix indicates reduced growth rates in later development. This pattern of change corroborates earlier studies on long bone histology. With the exception of a bone tissue found in the sample of Batrachotomus kupferzellensis, which might be the result of metaplastic ossification, the general mode of skeletogenesis is comparable with intramembraneous ossification. The lack of cancellous bone tissue and remodelling processes associated with bone ornamentation, as well as the predominantly intramembraneous mode of ossification, indicates that rauisuchian osteoderm formation differs profoundly from that of the osteoderms of the only extant pseudosuchian lineage, the crocodylians.

Taxonomy of Diplocynodon and Tooth Wear in Caiman latirostris

2011-09-15T11:25:00.001-04:00

Martin, Jeremy E. and Martin Gross. 2011. "Taxonomic clarification of Diplocynodon Pomel, 1847 (Crocodilia) from the Miocene of Styria, Austria" Neues Jahrbuch für Geologie und Paläontologie - Abhandlunge, 261:2 DOI: 10.1127/0077-7749/2011/0159

Abstract
A re-examination of the original type series of Prangner (1845) and Hofmann (1887a) of the primitive alligatoroids from the middle Miocene of Styria, led to a reappraisal of the taxonomy of the following species of Diplocynodon: D. steineri and D. styriacus. Of unsettled affinities, Enneodon ungeri was also re-examined. It is here demonstrated that it belongs to the same taxon of the specimens described by Hofmann (1887a). These taxa are in fact junior synonyms of the previously erected Enneodon ungeri. Moreover, comparison with other European alligatoroids reveals that the Austrian specimens described by Prangner (1845) and Hofmann (1887a) belong to the same genus: Diplocynodon Pomel, 1847. According to the rules of the International Commission on Zoological Nomenclature (ICZN), Diplocynodon has priority over Enneodon. Under the principle of priority, it is therefore proposed to rename all the Miocene remains of alligatoroids from Styria as Diplocynodon ungeri Prangner, 1845. Comparison of almost complete skulls from various Miocene contemporaneous localities reveals that there is no reason to erect another taxon for the French specimens of D. "styriacus" described in Ginsburg & Bulot (1997). However, these specimens need to be redefined as D. ungeri as well. D. ungeri was coded and included in a character matrix to cladistically test its affinities with other alligatoroids. A total of six species of Diplocynodon were analysed including: D. ratelii, D. hantoniensis, D. tormis, D. muelleri, D. darwini and D. ungeri. The results are consistent with previous studies and favour a monophyletic diplocynodontid clade. D. ungeri is the first species of the genus to be recognized from distant coeval European deposits, namely the Paris and the Pannonian Basins.

_____

Ősi, Attila and Paul M. Barrett. 2011. "Dental wear and oral food processing in Caiman latirostris: analogue for fossil crocodylians with crushing teeth" Neues Jahrbuch für Geologie und Paläontologie - Abhandlunge, 261:2 DOI: 10.1127/0077-7749/2011/0161

Abstract
Almost all of the 23 extant species of crocodylians are opportunistic predators that consume their food without extensive intraoral food processing. Posterior bulbous crushing teeth with heavy dental wear in two specimens of Caiman latirostris, however, indicate that oral food processing can be an important factor during feeding. Wear pattern analysis in two specimens of C. latirostris clearly indicates crushing of hard food items that produced large wear surfaces on tooth crowns in the posterior part of the tooth row. This type of wear suggests that the diet was predominantly composed of durable, hard-shelled prey (e.g.molluscs, crustaceans, turtles), a supposition confirmed by recent studies on the stomach contents of several C. latirostris specimens. The absence of similar wear patterns in other ontogenetically mature specimens of C. latirostris, however, indicates that specific, possibly regional differences in food resources might affect the degree and type of dental wear. The dental features we report in C. latirostris can provide an important extant analogue for fossil forms with similar dentitions (e.g. Bernissartia, Unasuchus and globidontan eusuchians).

Summer Field Work 2011 - Part 4 - Ghost Ranch

2011-09-02T17:49:00.001-04:00

My 10th and final week at PEFO was actually spent mostly outside of PEFO, at Ghost Ranch in New Mexico. At the last minute (with a little pushing from Bill), we interns decided to go join the fun (Bill had wilderness training, so he couldn't join us). We left late on Sunday, arriving Monday morning. We arrived just in time to meet up with Alan Turner, Michelle Stocker, and crew as they surveyed the lab and quarry. We would be working in the Hayden Quarry (know for its wealth of data associated with dinosaur origins as well as from the paintings of Georgia O'Keefe) and would soon be joined by a rather large field crew comprised of paleontologists from University of Utah (Randy Irmis et al), UC Berkely (Kevin Padian et al), and several other institutions. Due to the large number of people, Rachel, Chuck, and I would have to camp at the quarry instead of the Ghost Ranch campsite.


Hayden Quarry 2 and 4 as viewed from 3.

Last year, they had started working on a large block of Typothorax material, so our fist goal was to get that ready to be pulled out. Step 1 was cleaning off all the material that had fallen from the quarry wall over the year (lots and lots of shoveling involved). Then we had to add several more layers of plaster and continue excavating around the base of the jacket. This took quite a while because of the amount of bone that was in the rock around and underneath the jacket. We just collected the bone on top of the jacket whilst removing the "underburden" (read Bill's post on when a large quarry block becomes furniture).

Unfortunately, we couldn't stay for longer than a few days. And although we were still working in the Chinle Formation, it was a vastly different experience compared to working the Chinle of PEFO. We returned to the park in time for me to get to spend one last day in the field. Reflecting on those 10 weeks, I can certainly say that the Chinle can be a frustrating formation to work in but its wealth of data us well worth it. I just hope that I get to spend many more field seasons working in the Chinle, especially the PEFO Chinle.

Summer Field Work 2011 - Part 3

2011-09-02T16:28:00.000-04:00

Week 7

Surface bone. What could it be? (Photo by Andrea Thomer)

Phytosaur skull.

This was a somewhat slow week between office days and unproductive prospecting. Friday was spent back at Billings Gap where we had noticed several surface exposures of bone previously. Most of the bone we were finding was fragmentary and did not go far under the surface, a common frustration in the Chinle, but rule #7 is that if something catches your eye, you must examine it. So that afternoon, after prospecting for a while I started walking back to where Rachel was working on an aetosaur osteoderm, and something caught my eye. In the Chinle of PEFO, highly weathered bone is typically a dark purple or maroon, but what caught my eye was much lighter in color - a good sign. I started digging, and digging, and digging, and before long I had uncovered a complete phytosaur cranium. What had caught my eye turned out to be the parietals. Since it was getting late and the skull was so big, we would have to come back another day to finish excavating it and collect it. We dug a drainage ditch and covered it with a plastic bag. We'd be back.

Week 8

A metoposaur clavical with many other small bones.

Many of the small bones I found at Zuni Well Mound.

On Monday, we found out that we would have to leave the skull where we had found it for a little while. We would have to return to the skull to bury it and mark it in a way that would protect it and make it easy to return to in a few months. With that disappointment, we decided to take a slightly different approach to our field work that week. We headed out to a spot called Zuni Well Mound to quarry. It was a very productive microvertebrate site, but the bones were very fragile. It seemed like even looking at them would make them disintegrate. Despite that we were still able to collect a lot of material including metoposaurs, Vancleavea, fish, and even a partial dinosaur pes. It was mid week when we were finally able to go back out to bury the phytosaur. As we were leaving we decided to stop at a location that Berkley (in the 1980s) had nicknamed "Angry Man Flats" after a rancher had yelled at them for being there (even tho the land was technically BLM land and Berkley had a permit). Bill located an area that had a lot of surface bone. It seemed to be all coming from a single layer. A bonebed? We had to call in Kenny to bring us more supplies, but by the time he arrived we had found that a lot of the bone too weathered and did not go far under the surface. Kenny was not happy that he had been pulled out of the lab for this (leading to the new nickname of "Angry Kenny Flats"). We were still able to leave with several small jackets with the intention of returning.

Week 9

Prospecting on state land. Left to right: me, Zach, Sarah, Rachel, Matt, and Chuck (Photo by Andrea Thomer).

Most of the park employees had mandatory training for several days, but luckily we had some visitors to keep us busy. Matt Brown, former PEFO collections manager and current UT Austin collections manager, was in the area to do reconnaissance for next year's field season. Sarah Werning with assistant Zach Morris were in the area collecting herps for Berkley. We spent several days out prospecting on state land - the interns, our visitors, and Andrea (summer intern in the PEFO collections). We found enough bone to make it a good field site for UT Austin. Unfortunately we kept getting chased out by the monsoons.

One more week to come (including Ghost Ranch), so stay tuned.

And check out Andrea's blog on digitization!

Summer Field Work 2011 - Part 2

2011-08-31T10:12:00.000-04:00

Week 4

Excavating aetosaur plates at Billing's Gap.

Always buckle up for safety.

Petrified Forest is currently in a phase of expansion. The federal government has authorized the addition of 125,000 acres to the park which is composed of private, state, and federal (primarily Bureau of Land Management) lands. We spent a good portion of the week in the eastern part of that boundary expansion, including an area known as Billing's Gap (the place you go if you want a phytosaur skull). Besides doing field work, we also got to teach the park law enforcement what petrified wood theft looks like.

Somehow, we keep getting chased (law enforcement, horses, etc)

Week 5

Afternoon monsoons moving in.

The "purple layer", representing the Adamanian-Revueltian transition.

About halfway through my summer at PEFO, monsoon season arrived and the weather switched from sunny, super windy, and VERY hot (100 to 110+) to partly cloudy, breezy, and ~90 with a good chance of an afternoon thunderstorm most days. The week was mostly spent in the office with one day out on BLM land with Sierra College and another day spent with a documentary crew discussing the Adamanian-Revueltian transition.

Week 6

Partial mediolateral plate of a Typothorax.

Hiding from the noon sun in a shade cave at Karen's Point.

Bill left us for 4th of July weekend and the rest of the week to go to Disneyland with the family, but Chuck Beightol (a 2009 and 2010 intern) joined us. Left to our own devices, our first priority was to clean the office, something we were sure had never been done. We also had some of our own field projects in mind, the most productive of which was a day spent at Karen's Point where we collected specimens of several aetosaur species (Typothorax, Paratypothorax, and Heliocanthus) as well as lots of metoposaurs.

4 more weeks to go...

Summer Field Work 2011 - Part 1

2011-08-30T14:42:00.000-04:00

I have recently returned from 10 weeks of field work at Petrified Forest National Park (plus 2 weeks on the road with family) working with Bill Parker. Internet access was generally problematic at PEFO. Therefore, blog posts became an issue. And hey, it's hard, tiring work being in the field and most things that aren't food, sleep, or beer can get set aside. But I did take lots of notes and pictures, so I'll tell you a bit about my summer field work now:

Week 1:

Bill at the Bowman site, taking field notes.

My first day started a bit slow due to requisite air quality monitoring, but we did find a phytosaur quadrate before lunch. The rest of the week was spent learning the ropes along with two guys from Chaco Culture NHP. Chaco is known for it's archeological resources, but with recent findings in their Cretaceous bedrock, they hired a geocorps participant to do a paleontological inventory. So we had Jim (Chaco Natural Resources) and Phil (GeoCorps) out with us for a few days to learn how to do paleo field work and inventories from the best (Bill got his start doing paleo inventory work for the US Forest Service). We also had the new park superintendent join us one day. It was a pretty full truck. We spent most of our time at a location known as the Bowman Site, stratigraphically situated in the Jim Camp Wash beds of the Sonsela Member of the Chinle Formation, just above the Adamanian-Revueltian transition. We collected several vertebrae, armor plates, and other unarticulated bones. Our lovely fossil preparator, Kenny Bader, was even able to find some tiny freshwater shark teeth in the rock he cleaned from the other bones.

Week 2:

Rachel sitting next to the Yale fish.

Bill and Robin discussing the stratigraphy of the Petrified Forest Member.

My fellow intern and 2009 field season veteran, Rachel Guest, arrived. One day, we headed out to Chinde Mesa in the northern-most part of the park to visit a field crew from Yale. They had just flipped a block of aetosaur armor and found a nicely articulated fish underneath. We arrived just in time for lunch and 40+ mph winds. We also visited a group from Columbia College run by Robin Whatley who were camped out up at Pilot Rock in the northwest corner of the park. They were looking for microvertebrate sites - interested in taphonomy and early mammals. They also needed us to jump start their truck.

Week 3

Excavating a metoposaur clavical found by another ranger at the Dying Grounds.

Pilot Rock and the very colorful Owl Rock Member of the Chinle.

There is a lot of history present in Petrified Forest. This summer marked the 90th anniversary of when Charles Camp first started working in the park and since we have his field notes, we spent much of the week following in his footsteps. In doing so, we also came across signs of Ned Colbert (old wooden steaks from an erosion study) and the Civilian Conservation Corp of the Great Depression (a partially excavated petrified stump with newspaper from the 1930s). We also ended up at many different locations throughout the park with visiting research groups, including the "Giving Site" with Yale and back up to Pilot Rock with Robin Whatley and Kay Behrensmeyer. We ended the week at a Camp's Smilosuchus adamanensis quarry, exactly 90 years to the day (it happened to be a Friday for him as well).

Standing in Charles Camp's Smilosuchus quarry.

From Charles Camp's notebook, Friday, June 17th, 1921:

"Started work on the bed of bones discovered by Misses Kellogg in the steep bank about 50 feet above the arroyo that runs thru camp. Walked in a short distance over the soft bone and uncovered the back part of the lower jaws of a phytosaur - apparently a very long jawed form. Worked here all day in teeth of a biting wind blowing gravel in our faces. We could only proceed slowly as the bones are very soft and show tendency to crack as soon as exposed to the weather."

more to come...

The Early Evolution of Archosaurs

2011-06-25T14:57:00.000-04:00

I hope you all have seen Sterling Nesbitt's new monograph on the evolution and phylogenetic relationships of archosaurs. Below is the abstract as well as a link to the nearly 300 page paper.

It is one of the most comprehensive studies to date and has some major implications for archosaur origins and much of the crocodile-line. As Sterling himself says 'the most interesting outcome of the
phylogenetic position of phytosaurs as the sister taxon of Archosauria is that the classic ‘‘crocodile normal ankle’’ is rendered plesiomorphic for Phytosauria + Archosauria (= Crurotarsi)'. Obviously, this is a major, novel result and it certainly will have a great impact on the future direction of this blog.

For now, I will continue to post on phytosaurs and will asses their place in my posts as more data becomes available. I certainly have to reconsider the focus of this blog, whether I'll discuss all "forgtten archosaurs" or simply "crurotarsans" and/or croc-line archosaurs (depending on definitions).

A simplified phylogeny from the cover.

Nesbitt, S. J. 2011. "The early evolution of archosaurs : relationships and the origin of major clades." Bulletin of the American Museum of Natural History, no. 352 Online

Abstract

Archosaurs have a nearly 250 million year record that originated shortly after the Permian-Triassic extinction event and is continued today by two extant clades, the crocodylians and the avians. The two extant lineages exemplify two bauplan extremes among a diverse and complex evolutionary history, but little is known about the common ancestor of these lineages. Renewed interest in early archosaurs has led to nearly a doubling of the known taxa in the last 20 years.
This study presents a thorough phylogenetic analysis of 80 species-level taxa ranging from the latest Permian to the early part of the Jurassic using a dataset of 412 characters. Each terminal taxon is explicitly described and all specimens used in the analysis are clearly stated. Additionally, each character is discussed in detail and nearly all of the character states are illustrated in either a drawing or highlighted on a specimen photograph. A combination of novel characters and comprehensive character sampling has bridged previously published analyses that focus on particular archosauriform subclades.
A well-resolved, robustly supported consensus tree (MPTs 5 360) found a monophyletic Archosauria consisting of two major branches, the crocodylian-line and avian-line lineages. The monophyly of clades such as Ornithosuchidae, Phytosauria, Aetosauria, Crocodylomorpha, and Dinosauria is supported in this analysis. However, phytosaurs are recovered as the closest sister taxon to Archosauria, rather than basal crocodylian-line archosaurs, for the first time. Among taxa classically termed as ‘‘rauisuchians,’’ a monophyletic poposauroid clade was found as the sister taxon to a group of paraphyletic ‘‘rauisuchians’’ and monophyletic crocodylomorphs. Hence, crocodylomorphs are well nested within a clade of ‘‘rauisuchians,’’
and are not more closely related to aetosaurs than to taxa such as Postosuchus. Basal crocodylomorphs such as Hesperosuchus and similar forms (‘‘Sphenosuchia’’) were found as a paraphyletic grade leading to the clade Crocodyliformes. Among avian-line archosaurs, Dinosauria is well supported. A monophyletic clade containing Silesaurus and similar forms is well supported as the sister taxon to Dinosauria. Pterosaurs are robustly supported at the base of the avian line.
A time-calibrated phylogeny of Archosauriformes indicates that the origin and initial diversification of Archosauria occurred during the Early Triassic following the Permian-Triassic extinction. Furthermore, all major basal archosaur lineages except Crocodylomorpha were established by the end of the Anisian. Early archosaur evolution is characterized by high rates of homoplasy, long ghost lineages, and high rates of character evolution. These data imply that much of the early history of Archosauria has not been recovered from the fossil record. Not only were archosaurs diverse by the Middle Triassic, but they had nearly a cosmopolitan biogeographic distribution by the end of the Anisian.

Postosuchus heads to PEFO

2011-06-23T11:19:00.000-04:00

Toast-asuchus!

So, you've likely seen me post about my little Safari Ltd. Postosuchus toy. As I traveled out to Petrified Forest this summer, I took a series of photos of the little guy, searching for his home. Below are some of my favorites, complete with geologic context.

By the way, I would like to apologize for the lack of posts. Internet has been problematic.

On Rt 24, headed to Colorado Springs, CO. The road was built on the Paleogene Dawson Formation.

Postosuchus searches for home, but finds himself in the Ordovician Manitou Limestone at Cave of the Winds.

Still searching, Postosuchus ends up in the Paleoproterozoic Routt Granite of Royal Gorge.


Oops! Went too far and ended up in the Cretaceous Dakota Shale.

Getting closer, Postosuchus checks out Delicate Arch in the Jurassic Entrada Sandstone of Arches National Park, UT

He finally made it! See here in the Rainbow Forest Museum of Petrified Forest NP, situated in the Triassic Chinle Formation.

Metriorhynchid Functional Morphology and A New Baurusuchid

2011-05-09T16:47:00.000-04:00

Life reconstruction (by Rodolfo Nogueira) of Campinasuchus dinizi from Carvalho et al 2011.

Carvalho, I. D. S., V. D. P. A. Teixeira, M. L. D. F. Ferraz, L. C. B. Ribeiro, A. G. Martinelli, F. M. Neto, J. J. W. Seritch, G. C. Cunha, I. C. Cunha, and P. F. Ferraz. 2011. "Campinasuchus dinizi gen. et sp. nov., a new Late Cretaceous baurusuchid (Crocodyliformes) from the Bauru Basin, Brazil" Zootaxa 2871: 19-42 Open access online.

Abstract
A remarkably diverse terrestrial mesoeucrocodylian fauna has been recovered from the continental Cretaceous of the Bauru Basin in fluvial and lacustrine deposits. Members of at least six distinct groups are now recognized, including notosuchids, sphagesaurids, candidodontids, peirosaurids, trematochampsids, and baurusuchids. These mostly terrestrial crocodyliforms potentially developed ecological strategies that allowed them to live in a hot and arid climate during the Cretaceous. A new genus and species of Baurusuchidae, Campinasuchus dinizi gen. et sp. nov., is established on the basis of several partial skulls and skeletons from the Turonian-Santonian Adamantina Formation. This taxon is notable for its relatively short, anteriorly tapering snout, marked maxillary heterodonty with third maxillary and fourth dentary teeth extremely enlarged relative to other teeth, and the presence of a large anteroposterior depression on each palatine between the palatal fenestrae. The presence of yet another crocodyliform from the Adamantina Formation reinforces the idea that aridity, or maybe a seasonally warm and dry climate alternating with periods of higher rainfall, drove the diversification of terrestrial crocodyliforms throughout the Late Cretaceous.

Young, M. T., M. A. Bell, and S. L. Brusatte. 2011. "Craniofacial form and function in Metriorhynchidae (Crocodylomorpha: Thalattosuchia): modelling phenotypic evolution with maximum-likelihood methods." Biology Letters. Published online. doi:10.1098/rsbl.2011.0357

Abstract
Metriorhynchid crocodylomorphs were the only group of archosaurs to fully adapt to a pelagic lifestyle. During the Jurassic and Early Cretaceous, this group diversified into a variety of ecological and morphological types, from large super-predators with a broad short snout and serrated teeth to specialized piscivores/teuthophages with an elongate tubular snout and uncarinated teeth. Here, we use an integrated repertoire of geometric morphometric (form), biomechanical finite-element analysis (FEA; function) and phylogenetic data to examine the nature of craniofacial evolution in this clade. FEA stress values significantly correlate with morphometric values representing skull length and breadth, indicating that form and function are associated. Maximum-likelihood methods, which assess which of several models of evolution best explain the distribution of form and function data on a phylogenetic tree, show that the two major metriorhynchid subclades underwent different evolutionary modes. In geosaurines, both form and function are best explained as evolving under ‘random’ Brownian motion, whereas in metriorhynchines, the form metrics are best explained as evolving under stasis and the function metric as undergoing a directional change (towards most efficient low-stress piscivory). This suggests that the two subclades were under different selection pressures, and that metriorhynchines with similar skull shape were driven to become functionally divergent.

Poposaurus and the future of 'Crurotarsi'

2011-04-27T18:14:00.000-04:00

Like many rauisuchians, Poposaurus has been plagued with a lack of fossil material. However, a recent find in the Upper Triassic Chinle Formation of Utah has helped shed some light into this early archosaur. Although a skull still remains to be found, paleontologists have managed to uncover an almost complete post-cranial skeleton. What is also interesting is the phylogenetic analysis associated with the new Poposaurus material. The most startling result is that Phytosauria falls out of the crocodile side of the archosaur tree and becomes the sister taxon of Archosauria. Depending on your definition of Crurotarsi, this could mean that dinosaurs are crurotarsans. However, under the Sereno 2005 definition, Crurotarsi is safe. For now ;-). Rauisuchia may also be in trouble based on the new phylogeny, which preserves Poposauroidea, but not Rauisuchidae. A more detailed phylogeny by Sterling Nesbitt will be coming out soon in the Bulletin of the American Museum of Natural History.

Gauthier, J. A., Nesbitt, S. J., Schachner, E. R., Bever, G. S., and W. G. Joyce. 2011. "The bipedal stem-crocodilian Poposaurus gracilis: inferring function in fossils and innovation in archosaur locomotion." Bulletin of the Peabody Museum of Natural History 52: 107-126.

We introduce a spectacular new specimen of a Late Triassic stem crocodilian identified as Poposaurus gracilis. It is part of a poorly known group, Poposauroidea, that, because of its striking similarities with contemporaneous stem avians (“dinosaurs”), has long puzzled archosaur paleontologists. Observed vertebrate locomotor behaviors, together with exceptional preservation of distinctive anatomical clues in this fossil, enable us to examine locomotor evolution in light of new advances in phylogenetic relationships among Triassic archosaurs. Because this stem crocodilian is unambiguously an archosaur, a diapsid, a tetrapod and a choanate sarcopterygian, we can safely infer major components of its locomotor behavior. These inferences, together with form-function constraints, suggest that P. gracilis was a fleet-footed, obligately erect-postured,
striding biped. That behavior seems to have been superimposed on the ancestral archosaur’s innovative locomotor repertoire, which includes the capacity to “high walk.” These novelties persist in a recognizable form in archosaurs for at least 245 million years and are widely distributed across Earth’s surface in diverse ecological settings. They thus qualify as evolutionary innovations even regardless of significant differences in diversification rates among extant diapsid reptiles.

Crocs in JVP: Goniopholis and Metriorhynchus

2011-04-13T14:42:00.000-04:00

de Andrade, M. B. and J. J. Hornung. 2011. 'A New Look into the Periorbital Morphology of Goniopholis (Mesoeucrocodylia: Neosuchia) and Related Forms' Journal of Vertebrate Paleontology 31(2):352-368 doi: 10.1080/02724634.2011.550353

Abstract
The periorbital morphology of goniopholidids is discussed, exploring the diversity of patterns and the relevance of the data for phylogenetic studies. Revision of material is focused on Goniopholis spp. and aff. Goniopholis spp., from England, Germany, and Belgium, providing a comparative description of their interorbital morphology. Traditional interpretation of the interorbital elements in species of Goniopholis (G. simus, G. baryglyphaeus), where the frontal is interpreted as excluded from the orbit by a prefrontal-postorbital contact in the skull roof, is contested and clarified through the analysis of new specimens, including a morphometric analysis. In Goniopholis, failure to identify the palpebral and its subtle contact with the prefrontal has lead to misinterpretation of elements and structures near the orbit, and the differential preservation/loss of palpebrals explains variability of the orbit in shape and orientation. In all European goniophilidids the frontal reaches the primary orbital border and there is no prefrontal-postorbital contact on the dorsal surface of the skull. Extensive contact of the palpebral with the primary orbital border creates a secondary (functional) orbital border, from which the frontal is excluded in most taxa. The condition is not exclusive of European goniopholidids and is paralleled by protosuchids, peirosaurids, and baurusuchids. At least four main morphological patterns are recognized, revealing a high diversity of European goniopholidids.

Fernandez, M. B., A. P. Carabajal, Z. Gasparini, and G. C. Diaz. 2011. 'A Metriorhynchid Crocodyliform Braincase from Northern Chile' Journal of Vertebrate Paleontology 31(2):369-377 doi: 10.1080/02724634.2011.550361

Abstract
A three-dimensionally preserved metriorhynchid braincase from the Oxfordian of northern Chile is described. The specimen is referred to the metriorhynchid Metriorhynchus cf. M. westermanni. The excellent preservation provides clear sutures and a detailed description, and X-ray computed tomographic (CT) scanning provides internal anatomical details. The general pattern of the orbitotemporal region is consistent with that of the basal thalattosuchian Pelagosaurus typus as described recently. The specimen from northern Chile shares with other metriorhynchids (e.g., Cricosaurus araucanensis, Metriorhynchus westermanni, M. casamiquelai, and Dakosaurus andiniensis) a dorsally exposed laterosphenoid, a laterosphenoid-prootic suture forming a blunt crest separating the supratemporal fenestra into two fossae for muscular attachment, and the quadrate incompletely sutured to the braincase. Thus, these features characterize not only basal but derived Thalattosuchia, as suggested by previous authors. The main difference in the orbitotemporal region is that in the specimen described herein, and in the other metriorhynchids examined, the trigeminal fossa is developed mainly caudal to the trigeminal foramen, whereas in P. typus the fossa is developed rostral and caudal to the trigeminal foramen. CT scanning indicates the presence of enlarged dorsal dural venous sinuses overlying the brain, as it has been described recently in Steneosaurus pictaviensis, and a well-developed sinus within the quadrate. The large foramen ventrolateral to the occipital condyle, which characterizes metriorhynchids, is confirmed as the entry for the internal carotid artery.

Great Rauisuchian Find: Decuriasuchus quatracolonia

2011-04-13T14:28:00.001-04:00

Franca, M. A. G. and J. Ferigolo. 2011. 'Associated skeletons of a new middle Triassic "Rauisuchian" from Brazil' Naturwissenschaften (online first) DOI: 10.1007/s00114-011-0782-3

Abstract
For more than 30 million years, in early Mesozoic Pangea, “rauisuchian” archosaurs were the apex predators in most terrestrial ecosystems, but their biology and evolutionary history remain poorly understood. We describe a new “rauisuchian” based on ten individuals found in a single locality from the Middle Triassic (Ladinian) Santa Maria Formation of southern Brazil. Nine articulated and associated skeletons were discovered, three of which have nearly complete skulls. Along with sedimentological and taphonomic data, this suggests that those highly successful predators exhibited some kind of intraspecific interaction. Other monotaxic assemblages of Triassic archosaurs are Late Triassic (Norian-Rhaetian) in age, approximately 10 million years younger than the material described here. Indeed, the studied assemblage may represent the earliest evidence of gregariousness among archosaurs, adding to our knowledge on the origin of a behavior pattern typical of extant taxa.

Updates

2011-04-11T14:37:00.001-04:00

First of all, I'd like to apologize for the long hiatus. I've been back at the University of Maryland this semester, working and taking classes (and studying for the general and biology GRE), and time has gotten away from me. I'll be getting back to posts on crurotarsans soon.

The first thing that may interest you all is that this summer, I'll be coming at you live from Petrified Forest National Park. I'll be working as an intern there for approximately 10 weeks, doing "hardcore paleontology". I will be working with Bill Parker, a vertebrate paleontologist for the park, whom many of you may know from his blog Chinleana, which focusses on issues of the Late Triassic. Petrified Forest is known for it's petrified wood, but the Late Triassic Chinle Formation that dominates the park is also known for it's diversity of archosaurs, both crurotarsan and dinosaur.

Image by Jeff Marz.

Something else I just wanted to mention real quick is that last week, I was fortunate enough to attend an event on campus featuring an interview and Q&A session with Richard Dawkins. For those of you not familiar with Dr. Dawkins, he is a famous evolutionary biologist, intelligent design critic, and author. Some of his great popular science works on evolution include The Greatest Show on Earth: The Evidence for Evolution, The Selfish Gene, The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe without Design, The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution, Climbing Mount Improbable The Extended Phenotype: The Long Reach of the Gene (Popular Science), and River Out Of Eden: A Darwinian View Of Life. I am currently reading Unweaving the Rainbow: Science, Delusion and the Appetite for Wonder, which is the beautiful and rather inspiring thesis of how using science to unravel the mysteries of the universe can be a great source of wonder.

The event on campus the other evening focused on his views on evolutionary biology. Dr. Dawkins is an articulate, intelligent, and witty man. He received both applause and laughter throughout the interview and during the Q&A session, a student even thanked him for inventing the meme. I particularly liked that fact that he advocated for teaching evolution as early as age 7 and that the foundation for learning evolution (like the idea of descent with modification) could be laid as early as 4 or 5. He also suggested a shift in the order in which biology is taught. Many courses start with cell biology and progress towards macrobiology, often ending in evolution and ecology. Instead, he suggested evolution be taught first, which I absolutely agree with because it is indeed true that "nothing in biology makes sense except in the light of evolution" (quote by Theodsius Dobzhansky). In all, it was a great evening.

Happy Valentines Day!

2011-02-14T19:50:00.001-05:00

I hope you all are enjoying February 14th with someone special. And to help celebrate, I have the results of our latest poll. So, which crurotarsan clades do my lovely readers love? Rauisuchians (43%), followed by crocodylomorphs (25%)! A readership after my own heart. I almost feel a little bad for phytosaurs (7%), but that's what they get for being so tricky.

What is your favorite crurotarsan clade?

Neptunidraco

2011-02-09T12:07:00.000-05:00

Andrea Cau, study co-author, posing with the counter top and a reconstruction of Neptunidraco (from Nat Geo)

Meaning: "Neptune's dragon"
Species: N. ammoniticus
Nominal Author: Cau and Fanti, 2011
Age: Middle Jurassic
Location: Italy
General Description: A predatory, pelagic crocodyliform (metriorhynchid), several meters in length

You may remember my post from last May on Geosaurus in which I mentioned the "coccodrillo di Portomaggiore". At the time, Young and Andrade (2009) had proposed that the mystery croc belonged to the genus Geosaurus, but it was still awaiting a proper description. Well, the "coccodrillo di Portomaggiore" has finally been properly named and described in the March issue of Gondwana Research:

Cau, A. & F. Fanti. (2011) "The oldest known metriorhynchid crocodylian from the Middle Jurassic of North-eastern Italy, Neptunidraco ammoniticus gen. et sp. nov." Gondwana Research 19: 550-565. doi:10.1016/j.gr.2010.07.007

It is a very well written paper; my only criticism would be that the placement of the section on systematic paleontology and the diagnosis was a little later in the paper than I would have expected. Since this paper is the first on Neptunidraco (although there have been brief descriptions and mentions of the "coccodrillo di Portomaggiore" previously), I'm not going to do my usual "summary" of what is known about the genus, but I do highlight some interesting bits of the paper below:

Neptunidraco gen. nov. is preserved as partially disarticulated skull bones, an articulated mandible, teeth, and seven presacral vertebrae in four slabs of limestone (Rosso Ammonitico Veronese Formation), once destined to become a kitchen counter-top. Cau and Fanti also introduce a new clade name, Geosaurini nov., and define it as "the least inclusive clade containing G. giganteus, Geosaurus carpenteri, and Dakosaurus maximus." Their Strict Consensus Tree topology places Neptunidraco within Geosaurinae, just outside of Geosaurini. One thing that I found particularly interesting was Cau and Fanti's conclusion that Neptunidraco was not likely feeding on the bigger, crunchier prey of the time (ammonoids, crustaceans, armored fish, or other large marine vertebrates), but rather small, swift prey.

“What Should Everyone Know About Paleontology?” - Thomas R. Holtz, Jr.

2011-02-07T18:43:00.004-05:00

The title question was recently asked by Roberto Takata on the Dinosaur Mailing List and Dr. Tom Holtz took up the challenge. I have re-posted his answer bellow. Although you may have already seen this, I think this is an important topic and, of course, I think that the things Dr. Holtz discusses are things that everyone should know. Not to mention that, as a former student of Dr. Holtz, I generally like what he has to say. Enjoy:

Dr. Holtz discusses binocular vision in Tyrannosaurus during the annual Scholars in New York trip (2009)

“What Should Everyone Know About Paleontology?”

Thomas R. Holtz, Jr.

I think that is a good question. What really are the most important elements of paleontology that the general public should understand? I took a shot at coming up with a list of key concepts, based on experiences with teaching paleontology and historical geology and with less-formally structured outreach to the public. I have offered this list (cross posted at the Sauropod Vertebrae Picture of the Week, Dave Hone's Archosaur Musings, and Superoceras blogs) as a way for it to reach a wider audience. That this is Darwin Week makes it even more appropriate, as we should use this occasion to encourage a better understanding of the changes of Earth and Life through Time for the public at large.

Much as I might like to think otherwise, the specific details of the hindlimb function of Tyrannosaurus rex or the pneumatic features of brachiosaurid vertebrae really are not the most important elements of the field. Understanding and appreciating the nitty gritty details of the phylogeny and anatomy of any particular branch of the Tree of Life are not really necessary for everyone to know, any more than we would regard detailed knowledge of bacterial biochemistry or the partitioning of minerals in a magma chamber to be significant general knowledge. (Indeed, these latter two items are actually far more critical for human society than any specific aspect of paleontology, and so from a certain point of view really more important for people to know than the History of Life.)

That said, all human societies and many individuals have wondered about where we have come from and how the world came to be the way it is. This is, in my opinion, the greatest contribution of paleontology: it gives us the Story of Earth and Life, and especially our own story.

I have divided this list into two sections. The first is a list of general topics of paleontology, touching on the main elements of geology that someone would need to know for fossils to make any sense. The second is the more specific list of key points in the history of life.

(NOTE: as the idea of this list is that it should be aimed at the general public, I have tried to avoid technical terminology where possible.)

GENERAL:

That rocks are produced by various factors (erosion à sedimentation; metamorphism; volcanic activity; etc.)
That rocks did not form at a single moment in time, but instead have been and continue to be generated throughout the history of the planet.
That fossils are remains of organisms or traces of their behavior recorded in those rocks.
That rocks (and the organisms that made the fossils) can be thousands, millions, or even billions of years old.
That the species discovered as fossils, and the communities of organisms at each place and time, are different from the same in the modern world and from each other.
That despite these differences that there is continuity between life in the past and life in the present: this continuity is a record of the evolution of life.
That we can use fossils, in conjunction with anatomical, molecular, and developmental data of living forms, to reconstruct the evolutionary pattern of life through time.
That fossils are incomplete remains of once-living things, and that in order to reconstruct how the organisms that produced them actually lived, we can:

Document their anatomy (both gross external and with the use of CT scanning internal), and compare them to the anatomy of living creatures in order to estimate their function;
Examine their chemical composition, which can reveal aspects of their biochemistry;
Examine their microstructure to estimate patterns of growth;
Model their biomechanical functions using computers and other engineering techniques;
Investigate their footprints, burrows, and other traces to reveal the motion and other actions of the species while they were alive;
And collect information of the various species that lived together in order to reconstruct past communities.

However, with all that, fossils are necessarily incomplete, and there will always be information about past life which we might very much want to know, but which has been forever lost. Accepting this is very important when working with paleontology.
That environments of the past were different from the present.
That there have been episodes of time when major fractions of the living world were extinguished in a very short period of time: such data could not be known without the fossil record.
That entire branches of the tree of life have perished (sometimes in these mass extinction events, sometimes more gradually).
That certain modes of life (reef formers, fast-swimming marine predators, large-bodied terrestrial browsers, etc.) have been occupied by very different groups of organisms at different periods of Earth History.
That every living species, and every living individual, has a common ancestor with all other species and individuals at some point in the History of Life.

SPECIFIC:

Honestly, despite the fact the specific issues about specific parts of the Tree of Life are the ones that paleontologists, the news media, the average citizen, etc., are more concerned with, they really are much less significant for the general public to know than the points above. Sadly, documentary companies and the like keep on forgetting that, and keep on forgetting that a lot of the public does not know the above points.

Really, in the big picture, the distinction between dinosaurs, pterosaurs, and crurotarsans are trivialities compared to a basic understanding that the fossil record is our document of Life’s history and Earth’s changes.

Summarizing the key points of the history of life over nearly 4 billion years of evolutionary history is a big task. After all, there is a tendency to focus on the spectacular and sensationalized rather than the ordinary and humdrum. As Stephen Jay Gould and others often remarked, from a purely objective external standpoint we have always lived in the Age of Bacteria, and the changing panoply of animals and plants during the last half-billion years have only been superficial changes.

But the question wasn’t “what should a dispassionate outsider regard as the modal aspect of the History of Life?”; it was “What should everyone know about paleontology?” Since we are terrestrial mammals of the latest Cenozoic, we have a natural interest in events on the land and during the most recent parts of Earth History. That is a fair bias: it does focus on who WE are and where WE come from.

That said, here is a list of key concepts in the history of life. Other researchers might pick other moments, and not include some that I have here. Still, I believe most such lists would have many of the same key points within them.

Life first developed in the seas, and for nearly all of its history was confined there.
For most of Life’s history, organisms were single-celled only. (And today, most of the diversity remains single-celled).
The evolution of photosynthesis was a critical event in the history of Earth and Life; living things were able to affect the planet and its chemistry on a global scale.
Multicellular life evolved independently several times.
Early animals were all marine forms.
The major groups of animals diverged from each other before they had the ability to make complex hard parts.
About 540 million years ago, the ability to make hard parts became possible across a wide swath of the animal tree of life, and a much better fossil record happened.
Plants colonized land in a series of stages and adaptations. This transformed the surface of the land, and allowed for animals of various groups to follow afterwards.
For the first 100 million years or so of skeletonized animals, our own group (the vertebrates) were relatively rare and primarily suspension feeders. The evolution of jaws allowed our group to greatly diversify, and from that point onward vertebrates of some form or other have remained apex predators in most marine environments.
Complex forests of plants (mostly related to small swampland plants of today’s world) covered wide regions of the lowlands of the Carboniferous.
Burial of this vegetation before it could decay led to the formation of much of the coal that powered the Industrial Revolution and continues to power the modern world.
While most of the coal swamp plants required a moist ground surface on which to propagate, one branch evolved a method of reproduction using a seed. This adaptation allowed them to colonize the interiors, and seed plants have long since become the dominant form of land plant.
In the coal swamps, one group of arthropods (the insects) evolved the ability to fly. From this point onward insects were to be among the most common and diverse land animals.
Early terrestrial vertebrates were often competent at moving around on land as adults, but typically had to go back to the water in order to reproduce. In the coal swamps one branch of these animals evolved a specialized egg that allowed them to reproduce on land, and thus avoid this “tadpole” stage.
These new terrestrial vertebrates—the amniotes—diversified into many forms. Some included the ancestors of modern mammals; others the ancestors of today’s reptiles (including birds).
A tremendous extinction event, the largest in the age of animals, devastated the world about 252 million years ago. Caused by the effects and side-effects of tremendous volcanoes, it radically altered the composition of both marine and terrestrial communities.
In the time after this Permo-Triassic extinction, reptiles (and especially a branch that includes the ancestors of crocodilians and dinosaurs) diversified and became ecologically dominant in most medium- to large-sized niches.
During the Triassic many of the distinctive lineages of the modern terrestrial world (including turtles, mammals, crocodile-like forms, lizard-like forms, etc.) appeared. Other groups that would be very important in the Mesozoic but would later disappear (such as pterosaurs and (in the seas) ichthyosaurs and plesiosaurs) evolved at this time.
Dinosaurs were initially a minor component of these Triassic communities. Only the tall, long-necked sauropodomorphs were ecologically diverse during this time among the various dinosaur branches. However, a mass extinction event at the end of the Triassic (essentially the Permo-Triassic extinction in miniature) allowed for the dinosaurs to diversify as their competitors had vanished.
During the Jurassic, dinosaurs diversified. Some grew to tremendous size; some evolved spectacular armor; some become the largest carnivorous land animals the world had seen by this point. Among smaller carnivorous dinosaurs, an insulating covering of feathers had evolved to cover the body (possibly from a more ancient form shared by all dinosaurs). Among the feathered dinosaurs were the ancestors of the birds.
Other terrestrial groups such as pterosaurs, crocodile-ancestors, mammals, and insects continued to diversify into new habits.
During the Jurassic and (especially) the Cretaceous, a major transformation of marine life occurred. Green-algae phytoplankton were displaced by red-algae phytoplankton (which continue to dominate modern marine ecosystems). A wide variety of new predators—advanced sharks and rays, teleost fish, predatory snails, crustaceans with powerful claws, specialized echinoids, etc.—appeared, and the sessile surface-dwelling suspension feeders that dominated the shallow marine communities since the Ordovician became far rarer. Instead, more mobile, swimming, or burrowing forms became more common.
During the Cretaceous one group of land-plants evolved flowers and fruit and thus tied their reproduction very closely with animals. Although not immediately ecologically dominant, this type of plants would eventually come to be the major land plant group.
The impact of a giant asteroid—coupled with other major on-going environmental changes—brought an end to the Mesozoic. Most large-bodied groups on land and sea, and many smaller bodied forms, disappeared. The only surviving dinosaurs were toothless birds.
The beginning of the Cenozoic saw the establishment of mammals as the dominant group of large-bodied terrestrial vertebrates. Early on mammals colonized both the sea and the air as well.
During its beginning the Cenozoic world was warm and wet, much like the Cretaceous. However, a number of changes of the position of the continents and the rise of mountain ranges caused the climates to cool and dry.
As the world cooled and dried, great grasslands developed (first in South America, and later nearly all other continents).
Various groups of animals adapted to the new grassland conditions. Herbivorous mammals became swift runners with deep-crowned teeth, often living in herds for protection. Mammalian predators became swifter as well, some becoming pack hunters.
Other new plant communities evolved, and new animal communities which inhabited them. The rise of modern meadows (dominated by daisy-related plants and grasses) saw the diversification of mouse-and-rat type rodents, many frogs and toads, advanced snakes, songbirds, etc.
A group of arboreal mammals with very big brains, complex social communities, and gripping hands—the primates—produced many forms. In Africa one branch of these evolved to live at mixed forest-grassland margins, and from this branch evolved some who became fully upright and moved out into the grasslands.
This group of primates retained and advanced the ability to use stone tools that its forest-dwelling ancestors already had. Many branches evolved, and some developed even larger brains and more complex tools. It is from among these that the ancestors of modern humans and other close relatives evolved, and eventually spread out from Africa to other regions of the planet.
About 2.6 million years ago a number of factors led to ice age conditions, where glaciers advanced and retreated. Various groups of animals evolved adaptations for these new cold climates.
The early humans managed to colonize much of the planet; shortly after their arrival into new worlds, nearly all the large-bodied native species disappeared.
At some point before the common ancestor of all modern humans spread across the planet, the ability to have very complex symbolic language evolved. This led to many, many technological and cultural diversifications which changed much faster than the biology of the humans themselves.
In western Asia and northern Africa (and eventually in other regions), modern humans developed techniques to grow food under controlled circumstances, leading to true agriculture. (Other cultures are known to have independently evolved proto-agricultural techniques).
This Neolithic revolution allowed for the development of more settled communities, specialization of individual skills within a community (including soldiers, metallurgists, potters, priests, rulers, and with the rise of writing, scribes).
From this point we begin to get a written record, and so the historians can take up the story…

This list is obviously not comprehensive, and there are many elements that I had to ignore to keep it relatively short. Still, I hope this overview helps put where we as a species fit into the larger perspective of Life’s long voyage, a voyage that could only have been traced by the study of fossils.

New Poll

2011-02-07T18:03:00.000-05:00

I have two feature posts in the works, both of which are Mesozoic crocodylomorphs. With that in mind and after reviewing my earlier posts, I thought it would be fun to get your opinions on your favorite crurotarsan clade, both for fun and so I can better gauge my readership, so check out the poll to the left and cast your vote. And of course, not every crurotarsan fits into the five clades I list, but it's just a poll. Also, since 4 out of 5 clades listed in the poll lived only in the Triassic, there may be some bias. I'll probably do a "crocodylomorph" poll and maybe even a "crown group" poll in the future.

Enjoy and stay tuned for those Mesozoic crocodylomorphs!

Pseudopalatus

2011-01-18T22:06:00.001-05:00

Pseudopalatus. Image modified from original by Jeff Martz.

Meaning: "false palate"

Species: P. pristinus Mehl, 1928; P. buceros Cope, 1881; P. mccauleyi Ballew, 1989; and P. jablonski Parker and Irmis, 2006

Nominal Author: Mehl, 1928

Age: Late Triassic

Location: Southwestern USA

Physical Characteristics: A large (3-4 meter) phytosaur with a robust rostrum and distinct dorsal crest.

Phylogenetic Position and Species Status

Currently, there are four species of Pseudopalatus, with P. pristinus and P. buceros being the most closely related and most derived and P. jablonskiae being the most basal (Parker and Irmis, 2006). It has been suggested multiple times that P. pristinus and P. buceros are sexual dimorphs of a single species (Camp, 1930; Colbert, 1947; Lawler, 1979; Zeigler et al, 2002; Zeigler et al, 2003), but the evidence is still inconclusive. The validity of P. mccauleyi as a species has also been contested (Long and Murry, 1995; Zeigler et al, 2002; Zeigler et al, 2003), but recent phylogenetic analyses have supported its position, especially when the newest species, P. jablonskiae, is considered (Ballew, 1989; Hungerbuhler, 2002; Parker and Irmis, 2006). The genus Pseudopalatus has been found to be most closely related to Redondasaurus, followed by Mystriosuchus, and when these three are combined with Nicosaurus, they constitute Pseudopalatinae (Hungerbuhler, 2002; Parker and Irmis, 2006).

Phylogeny of Pseudopalatinae from Hungerbuhler, 2002 (47 characters; tree length: 113; CI: 0.73; RI: 0.54; bootstrap values shown). A similar MPT was recovered by Parker and Irmis, 2006, with the addition of the newer species, P. jablonskiae (which was found to be the most basal member of Pseudopalatus).

A Revised Diagnosis of Pseudopalatus

With the addition of P. jablonskiae, Parker and Irmis revised the diagnosis of the genus in 2006. They included four of Hungerbuhler's characters, which include a strongly developed medial lamella of the postorbito-squamosal bar with the supratemporal fenestra reduced to a slit (character 19), a rounded top of the parieto-supraoccipital complex (character 24), the lamina of the squamosal extends onto the paroccipital process forming the ventrolateral border of the posttemporal fenestra (character 38), and a posttemporal fenestra less than three times wider than high (character 41) (2002). Pseudopalatus also differs from all other phytosaurs in that the dorsal position of the squamosals are mediolaterally expanded forming a shelf level with the parietal and postorbital (Parker and Irmis, 2006). Finally, Pseudopalatus differs from Redondasaurus in having a supratemporal fenestra that is visible in dorsal view.

Biostratigraphy

Pseudopalatus is a stratigraphically significant taxon. Lucas and Hunt (1993) designated Pseudopalatus as an index taxon for the Revueltian (early-middle Norian), with the first appearance datum for Pseudopalatus representing the end of the Adamanian land vertebrate faunachron and the beginning of the Revueltian land vertebrate faunachron. The addition of P. jablonkiae is significant in that it is the stratigraphically lowest occurrence of Pseudopalatus, suggesting an overlap of the Adamanian and Revueltian LVFs (Parker and Irmis, 2006).

Happy 2011!!! (and reasons I love Safari Ltd)

2011-01-06T16:09:00.001-05:00

I'm back after the hectic holidays. I hope you all survived and had a great new year. In the spirit of the holidays, I present Christmas Postosuchus:

I was in a toy store, shopping for my nephew when I cam across Safari Ltd.'s Postosuchus. In case you've never surfed Safari Ltd's website, I highly recommend that you do. They also have Deinosuchus, a crocodile (several actually, including a saltwater croc), an alligator (with babies), as well as many other great prehistoric critters.

However, my nepher is only 19 months old, so I got him this cute little croc and kept Postosuchus for myself.

Simosuchus - JVP Memoir 10

2010-12-09T16:26:00.000-05:00

Those of us who have payed any attention to the evolutionary history of crocodilians cringe when we hear them referred to as "living fossils". With the release of the new Memoir from the Society of Vertebrate Paleontology, this phrase is being thrown a round a lot. I generally detest the use of phrases like "living fossil" or "missing link" for many reasons. One article from the BBC was particularly hard to read, with statements like the following, making it sound like it is breaking news that crocs have a diverse evolutionary history.

"Yet contrary to popular belief, scientists now suggest that the basic body structure of crocodiles, alligators and ghariels evolved from a diverse group of prehistoric reptiles with different body shapes." - Ella Davies, BBC News

Even the press release from the Society of Vertebrate Paleontology had me worried for a moment. But I shouldn't allow misnomers to distract from the real news. The new Memoir, focusing on the pug-nosed Simosuchus, promises a great overview of crocodylimform anatomy.

'As strange as Simosuchus was, the incredible completeness and preservation of its fossils, coupled with an equally impressive scientific investigation, have yielded one of the most comprehensive volumes of crocodyliform anatomy ever to be published. “Very few crocodyliforms – even those alive today – have been subjected to this level of analysis,” said Brochu. “This reference is going to be used for decades.”' - SVP press release

I will post a more thorough description of Simosuchus and the new Memoir once I have received it in the mail.

Citation:
D. W. Krause and N. J. Kley (eds.), Simosuchus clarki (Crocodyliformes: Notosuchia) from the Late Cretaceous of Madagascar. Society of Vertebrate Paleontology Memoir 10. Journal of Vertebrate Paleontology 30(6, Supplement).

Baurusuchus

2010-12-03T13:18:00.001-05:00

Restoration of Baurusuchus salgadoensis sp. nov. from Carvalho et al., 2005 (art by Deverson da Silva)

Meaning: "Bauru crocodile", from the Bauru Group

Species: B. pachecoi Price, 1945; B. salgadoensis Carvalho et al., 2005; and B. albertoi Nascimento and Zaher, 2010

Nominal Author: Price, 1945

Age: Late Cretaceous

Location: Brazil

Physical Characteristics: approx. 3.5 to 4 meters in length, cursorial predator

Bauru Group - Adamantia Formation
All three species of Baurusuchus, as well as a 4th baurusuchid named Stratiotosuchus maxhechti, come from the Adamantia Formation of the Bauru Group in Brazil. The siliciclastic sediments of the Bauru Group are characteristic of the floodplain of a braided river in a hot, dry climate (Fulfaro et al., 1994). Baurusuchus shared its habitat with other crocodylomorphs including notosuchids, trematochampsids, and pairosaurids and may have even competed with theropod dinosaurs (abelisaurids)(Gasparini et al., 1993). It has also been suggested that Baurusuchus would dig holes as a source of water during dry periods, much like the "gator holes" of modern alligators (Carvalho et al., 2005).

Cranial Features
The cranial anatomy of baurusuchids is well known. Price (1945) described the Baurusuchidae as crocodilians with elongate, laterally compressed skulls. One unique feature of Baurusuchus pachecoi, the type species, is that the dermal bones of its skull are ornamented with irregular ridges. Baurusuchus salgadoensis differs from B. pachecoi is several ways, but the most striking is the presence of an antorbital fenestra (Carvalho et al., 2005). Unfortunately, the skull of the newly described Baurusuchus albertoi is only fragmentary but preserves a triangular infratemporal fenestra and a parallelogram-shaped external mandibular fenestra (Nascimento and Zaher 2010).

Baurusuchus skulls from Carvalho et al., 2005

Postcranial Skeleton
Nascimento and Zaher (2010) recently named a new species, Baurusuchus albertoi, and provided the first detailed description of postcranial material belonging to a member of the Baurusuchidae. Although they consider many of the observed postcranial features to be plesiomorphic (being present in other notosuchians), several unique sacral and carpal features were described. These include a dorsoventrally deflected transverse process of the sacral vertebrae, a longitudinal crest along the lateral surface of the sacral vertebrae, and a condyle-like surface of the pisiform carpal (Nascimento and Zaher 2010). Baurusuchus albertoi also possessed elongate cervical neural spines, enlarged zygopophyses, and separated prezygopophyses, allowing for marked dorsoventral cervical movement (Pol, 2005), suggesting an erect posture (Nascimento and Zaher 2010).

Cervical vertebrae of B. albertoi from Nascimento and Zaher, 2010. Scale bar = 10cm

Hi!

2010-11-15T13:26:00.001-05:00

Time seems to have gotten away from me once again, but not without reason. I left my job at the end of October, so I have been dealing with that transition. I left for a number of reasons, but most importantly is that I plan to return to school. I will be taking classes at the University of Maryland this spring as I prepare for and take the GRE, apply to graduate programs, and otherwise prepare for grad school. That has been the good distraction. Unfortunately, at the beginning of October, someone very close to me was diagnosed with a massive brain tumor, so the vast majority of my attention has been focused on him. He had surgery on November 2nd to remove the tumor. Thankfully, he is recovering wonderfully.

Despite all of these goings-on, this blog and my favorite clade have still been on my mind. I will update soon with a featured genus/species, but I also have a few other new ideas for posts including guest posts and museum profiles with a focus on their representation of crurotarsans.

In the mean time, I will leave you with this. I've been cleaning out my office and came across some old things from high school, including a bunch of articles I had clipped from newspapers and magazines on all things paleontological. The one that really caught my eye was from the Fall 2004 issue of National Parks magazine about fossils in national parks and the Paleontological Resource Preservation Act. The article focused heavily on Petrified Forest NP, with these two great pictures to illustrate that the park has more than just a bunch of petrified trees.

"True to their prehistoric focus, Arizona's Petrified Forest National Park boasts a full Postosuchus skeleton mold."

"Finds like this crocodile-like Phytosaur offer keys to understanding Petrified Forest National Park's natural and cultural resources, and unraveling the mysterious landscape that once existed here."

What's scarier than a rauisuchian?

2010-10-21T10:01:00.000-04:00

So, how do you celebrate Halloween? This is my pumpkin from last year - an attempt at Postosuchus. I'd say I did a pretty good job, considering I was working with a pumpkin. Some of the teeth may be a little off, but I think I got all of the fenestrae right. I'm thinking I might have to do Poposaurus this year, but I'm open to suggestions.

SVP Annual Meeting 2010 - Evening Events and Final Stats

2010-10-18T15:56:00.001-04:00

This year's meeting turned out to be the largest meeting on record at 1,190 attendees and at last count 761 abstracts submitted, the previous record holder being Austin, Texas in 2007. The 28th Annual Benefit Auction and Social went wonderfully, raising $18,500 dollars for the SVP Education and Research Fund. The theme was Star Trek, but we had bets going for the following themes: Lady Gaga, Avatar, Iron Man (and other such super heroes), Alice In Wonderland, and so on.

Although there was no banquet this year, they still held the awards ceremony to a full room. Here are the winners of the two big awards:

Alfred Sherwood Romer Prize
"The Alfred Sherwood Romer Prize recognizes an outstanding scientific contribution in vertebrate paleontology by a predoctoral student. Selection for participation in the Romer Prize Session at the SVP Annual Meeting is based on the scientific value and quality of an abstract summarizing an original research project, and the Romer Prize is awarded on the basis of the scientific value and quality of the oral presentation of that research during the Romer Prize session a the SVP Annual Meeting."
Winner: Jennifer Olori for her presentation on "DEVELOPMENTAL FEATURES OF MICROSAURS (LEPOSPONDYLI), AND CONSEQUENCES FOR THE EVOLUTION OF DEVELOPMENT AND PHYLOGENETIC RELATIONSHIPS WITHIN TETRAPODA"

Romer-Simpson Medal
"The A.S. Romer - G.G. Simpson medal, the society's highest award, is awarded for sustained and outstanding scholarly excellence in the discipline of vertebrate paleontology."
Recipient: Dr. Rinchen Barsbold

Congratulations to all of the award winners!

And we can't forget the after party, which concluded with Dr. Tom Holtz leading everyone in Walk The Dinosaur.

One last thing:
The issue of the embargo policy has come up with my coverage of the meeting, so for clarity's sake, I have included the policy below. That being said, there are always embargo policies of other publications and institutions to consider, as well as the wishes of the scientists whose work is being presented. Therefore, if anyone ever wishes for content to be removed from the blog, for any reason (although some reason is preferable), I will be happy to remove it (or change it) ASAP. Just shoot me an email. Jeopardizing someone's career is the last thing I want to do.

SVP Embargo Policy:
"Unless specified otherwise, coverage of abstracts presented orally at the Annual Meeting is strictly prohibited until the start time of the presentation, and coverage of poster presentations is prohibited until the relevant poster session opens for viewing. As defined here, “coverage” includes all types of electronic and print media; this includes blogging, tweeting and other intent to communicate or disseminate results or discussion presented at the SVP Annual Meeting. Content that may be pre-published online in advance of print publication is also subject to the SVP embargo policy."

SVP Annual Meeting 2010 - Part 3

2010-10-17T17:50:00.000-04:00

Tuesday was really the day for crurotarsans, with an entire session dedicated to crocodylomorphs and 14 posters covering a large diversity of the clade. Here's a quick list of them all.
Talks:

"Phylogenetic analysis of goniopholidid crocodyliforms of the Morrison Formation" by Eric Allen
"The evolution of trematochampsid crocodyliforms in Africa: new evidence from the Middle Cretaceous Galula Formation, Southwestern Tanzania" by J. Sertich and P. O'Connor
"A new baurusuchid (Crocodyliformes, Sebecosuchia) from the Bauru Group, Late Cretaceous of Minas Gerais, Brazil" by F. Montefeltro and M. Langer
"A reevaluation of the crocodyliform Acynodon from the Late Cretaceous of Europe" by A. Turner and C. Brochu
"New large blunt-snouted dyrosaurid (Mesoeucrocodylia) from the Paleocene of Columbia" by A. Hastings, J. Bloch, and C. Jaramillo
"Crocodylians from the Uinta Formation (Middle Eocene, Uintan) of western North America, response to climate change and the origins of Alligator" by C. Brochu and D. Snyder
"New material of Mekosuchus inexpectatus (Crocodylia: Mekosuchinae) from the Late Quaternary of New Caledonia, and the phylogenetic relationship of Australasian Cenozoic crocodylians" by S. Salisbury, T. Holt, T. Worthy, C. Sand, and A. Anderson
"Atmospheric hypoxia increases bone robusticity in the American Alligator" by T. Owerkowicz, E. Andrade, R. Elsey, K. Middleton, and J. Hicks
"Osteohistological analysis of Alligator mississippiensis indicates absense of fibrolamellar bone in crocodylians and confirms determinate growth with first report of external fundamental systems: implications for tetrapod osteohistology" by H. Woodward and J. Horner
"Mandibular mechanics of Alligator mississippiensis from beam models to finite element analysis" by L. Porro, D. Reed, J. Lemberg, U. Zapata, and C. Ross

Posters:

"Asymmetric skeletal adaptation to a debilitating pathology in the hindlimb of Poposaurus gracilis (Archosauris: Poposauroidea)" by M. Shirley, E. Schachner, and C. Shaw
"A metriorhynchid crocodyliform braincase from Northern Chile" by M. Fernandez, A. Paulina Carabajal, Z. Gasparini, Y. Herrera, and G. Chong
"Clarification of the skeletal anatomy of phytosaurs based on comparative anatomy and the most complete specimen of Angistorhinus" by M. Stocker
"The axial skeleton of Gracilisuchus stipanicicorum: autapomorphic charactersand its phylogenetic information within the context of Crurotarsi" by A. Lecuona
"Towards a stable phytosaur taxonomy: distinguishing characteristics between Pseudopalatus and Redondasaurus (Phytosauridae: Pseudopalatinae)" by M. Mancini and A. Hungerbuchler
"First occurence of the marine crocodyliform Terminonaris from the Upper Cretaceous (Turonian) of Manitoba" by J. Hatcher and A. Janzic
"New occurrence of the long-snouted crocodyliform, Terminonaris cf. t. robusta, from the Woodbine Formation (Cenomanian) of Texas" by T. Adams, M. Polcyn, O. Mateus, D. Winkler, and L. Jacobs
"One or two species of the giant crocodylian Deinosuchus?" by D. Schwimmer
"Dinosaurs walk tall: a crocodilian trace from the Lance Formation (Upper Cretaceous) of Wyoming" by P. Manning, J. Milan, and P. Falkingham
"A unique Eocene crocodylian from the Uinta Basin, Utah" by S. Masters, S. Sandau, D. Burk, and L. Krumenacker
"Crocodyliforms from the Early Miocene Domo De Zaza locality of Cuba" by O. Jimenez Vazquez and C. Brochu
"The pulmonary anatomy of Alligator mississippiensis: a unideirectional air flow system that foreshadows the avian respiratory system" by R. Sanders and C. Farmer
"Chronic exercise does not alter limb bone morphology or microstructure in the American Alligator (Alligator mississippiensis) " by H. Tsai, T. Owerkowicz, K. Felbinger, F. Andrade, and J. Hicks
"The nose knows: the effects of nasal cavity anatomy on airflow in alligators" by J. Bourke and L. Witmer
"Estimation of crocodilian body form from snout-vent length and tail girth" by G. Hurlburt

SVP Annual Meeting 2010 - Part 2

2010-10-13T19:57:00.001-04:00

So, yesterday was a big day for crurotarsans (although Crocodylomrpha was most widely represented) and the Romer Prize Session on Monday also included some very good croc talks.

Romer Prize Session:
For those of you who are not as familiar with SVP "the Alfred Sherwood Romer Prize recognizes an outstanding scientific contribution in vertebrate paleontology by a predoctoral student." The Romer Prize Session is a series of talks held during the meeting in which one speaker is then chosen as the winner of the Aldred Sherwood Romer Prize and the winner is announced at the awards ceremony on the last night of the meeting. Below, I list the talks from the session that were pertinent to the clade Crurotarsi, as well as any notes I had on the talk.

"Tooth pressure, niche occupation and the evolution of the cranial ecomorphology of crocodylians." by P. Gignac.

discussed how body size is mostly able to explain bite force and that tooth pressure in crocodylians often exceeds the shear stress limit of bone
produced a model that was able to predict individual bite force, giving insight into individual variation

"Seasonality as a potential source of variation in Alligator cranial evolution." by R. Sadleir

This was an excellent talk (partially because epigenetics were discussed) focusing on phenotypic plasticity as affected by seasonality (and aseasonality)
studied ranch animals and wild animals from the same breeding population (also was very good at taking into account many other variable that may have also been sources of phenotypic plasticity)
showed how seasonal vs aseasonal environments induced large amounts of phenotypic plasticity that may explain some instances of speciation within Alligator

"Evolution of salt-water tolerance in the Crocodylia and related crocodylomorphs: new insights from stable isotopes." by P. Wheatley

distribution and phylogeny suggests salt-water tolerance as an ancestral trait in crocodylomorphs, evolving at least as far back as Dyrosauridae + Crocodylia and becoming secondarily lost in alligators and gharials
since it is quite reasonable to assume that thalattosuchians were salt-water tolerant, they can be used as a geochemical proxy for salt-water tolerance in fossils (using carbon isotopes to show access to marine food sources and oxygen isotopes to show marine vs. freshwater "drinking")
Evidence suggests that dyrosaurids were salt-water tolerant and possibly even pelagic. If they were indeed pelagic, why did dyrosaurids survive the K-T extinction when so many other large taxa living in the same environment went extinct? Perhaps the juveniles were living in a freshwater environment (in fact, an audience member confirmed the presence of juvenile dyrosaurids in freshwater sedimentary environments).

If you ask me, I think both Sadleir and Wheatly are good candidates for the Romer Prize. Other talks of note were Jen Olori's talk on "Developmental featured of Microsaurs (Lepospondyli)", J. Scannella's talk on "Triceratops: A Model Organism for Deciphering Dinosaur Heterochrony" (this was a phenomenal talk, but may not get the Romer Prize because he did not focus enough on his own personal role in the research), and M. Spaulding's talk on "Phylogeny of the Carnivoramorpha". Stay tuned to hear about the winner of the prize.

Monday afternoon also yielded a few more talks on Crurotarsans, including one on a phytosaur, Pseudopalatus (although it was a somewhat poor talk), and a fantastic talk on the phylogenetic position of Thalattosuchia.

"Fossil crocodyliforms and turtles from the Early Cretaceous of Northeastern Mali" by Hill et al
"The endocranium, inner ear, and pneumatic structure of the Upper Triassic phytosaur Pseudopalatus pristinus" by Smith et al
"Thy phylogenetic position of Thalattosuchia (Crocodylomorpha) and the importance of outgroup choice" by Eric Wilberg
"Opportunism, acoustics and mass: exaptation and patterns of middle-ear expansion in Archosauria" by Dave Dufeau and Larry Witmer

More on Tuesday talks and the auction later.

Happy National Fossil Day!

2010-10-13T11:03:00.000-04:00

Today is the first ever National Fossil Day, as a part of Earth Science Week. The National Park Service and American Geological Institute have partnered to host this great event.

The stated mission of the event is such: National Fossil Day is a celebration organized by the National Park Service to promote public awareness and stewardship of fossils, as well as to foster a greater appreciation of their scientific and educational values.

I think we can all appreciate the importance of this mission. Please, check out the website (link above) to learn more about the goals and events surrounding National Fossil Day.

SVP Annual Meeting 2010 - Part 1

2010-10-12T10:17:00.000-04:00

The annual meeting of the Society of Vertebrate Paleontology has been great so far. Pittsburgh is a gorgeous city, with the David L. Lawrence Convention Center overlooking the Allegany River, and the weather has been perfect.

The representation of Crurotarsi at the meeting has started out slow. On Saturday evening, there was a get together of croc workers (mostly Chris Brochu and students) that I attended, but being held in a bar, little discussion of crocs actually took place. Sunday had just about the same amount of crurotarsan content, with only two posters (although quite excellent posters) discussing vertebrates of the Chinle Formation (Petrified Forest area, Arizona):

"A new vertebrate fossil locality in the upper Triassic Chinle Formation of Northeastern Arizona" by J. Weinbaum and J. Martz
"Understanding and utilizing detailed biostratigraphic data to characterize Late Triassic faunal change: examples from western North America" by J. Martz and W. Parker

Sunday evening was the welcome reception at the Carnegie Museum, which I believe illustrates my reason for naming this blog "Forgotten Archosaurs" quite well. The showcase exhibit of the museum that night was Dinosaurs in Their Time, the Mesozoic hall. After you pass Herrerasaurus to enter the hall, you are greeted by none other than Redondasaurus (shown below).

There are two other skulls of crurotarsans and a shale slab with a squished thalattosuchian to be found in the entire hall. And so, a clade that so dominated the landscape and overshadowed the dinosaurs for the first 50 million years of the Mesozoic and still retained quite a presence (especially in the marine realm as Thalattosuchia and Dyrosauridae) for the remainder of the era, is represented by only 4 species and only one full mounted display, in a hall called Dinosaurs in Their Time. So maybe they aren't entirely forgotten, but "incredibly unappreciated archosaurs" doesn't sound as catchy. And at least the Nile croc got a cool display in the Cenozoic hall (aka. the Mammal Hall...).

Society of Vertebrate Paleontology Annual Meeting 2010

2010-10-08T10:22:00.000-04:00

Tomorrow, I depart for the 70th Anniversary Meeting of the Society of Vertebrate Paleontology, held October 10th through the 13th at the David L. Lawrence Convention Center & Westin Convention Center in downtown Pittsburgh, Pennsylvania (USA). This year's meeting is being hosted by the Carnegie Museum of Natural History, which is excited to show off its recently renovated Mesozoic gallery, Dinosaurs in their Time, at the welcome reception Sunday night.

This year's logo features Fedexia striegeli, a tremotopid amphibian from the Late Pennsylvanian of Western Pennsylvania. Fedexia was only just recently published by Carnegie Museum paleontologists in the museum's publication Annals of Carnegie Museum (Berman et al 2010).

As usual, this years talks look like they will be dominated by dinosaurs and mammals, but Tuesday will be the day for Crurotarsans, with an entire afternoon session dedicated to them. I will be posting all that I can about all the new insights into our favorite archosaurs, as well as any other interesting happenings at the meeting, but I do take SVP's embargo policy very seriously. Stay tuned. I am very excited for the meeting and I hope you are too! I hope to see you there!

Wrong side of the Archosaur tree, but still a great cause

2010-10-04T09:09:00.002-04:00

You probably already know, but October is Breast Cancer Awareness Month. My grandmother died two years ago of breast cancer that metastasized to her liver and I live in a cancer cluster (over a dozen women in my neighborhood have been diagnosed in the past few years), so this is something close to my heart.

Over at the blog ART Evolved, they have found a unique way to make a difference. For the whole month of October, they are hosting the Pink Dinosaur Fundraiser for Cancer Research. There are two ways to participate: 1.) Go directly to the event page and donate or 2.) send in a picture of a pink dinosaur. For each dino they receive, they will donate $1. I've already sent in two:

Adult Triceratops (formerly Torosaurus)

Leptoceratops

The Gharial

2010-10-03T19:08:00.002-04:00

Male Gharial, sporting a large ghara

Species: Gavialis gangeticus (extant) and Siwaliks Gavialis (extinct)
Meaning: derived from Hindi "ghariyal"
Age: Pliocene to now
Location: India and Nepal
Physical Characteristics: up to 6 meters in length, longirostrine (although snouts become shorter and thicker with age) piscivores, possessing laterally flattened tails and webbed hind feet. Males possess "ghara" - a bulbous growth on the tip of the snout - for which they are named.

Modern Conservation Issues
Here at Forgotten Archosaurs, I usually deal with crocs that have long been extinct, but here we have an extant species that is critically in danger of joining those ranks. Gharials once lived in almost every river in India and the surrounding region but are today confined to only about 250 square km in India and Nepal, with the largest breeding population living in the National Chambal River Sanctuary (Whitaker 2007). There has been a fairly steady decline over the past century or so due to hunting and loss of habitat, but the loss of Gharials greatly increased starting in the late 1990s, changing their status from Endangered to Critically Endangered. In 1997, it was estimated that the total number of mature Gharials in the wild was 342 (Sharma and Basu 2004, Maskey 1999). By 2006, that number had decreased to only 182 individuals (Whitaker 2007). This rapid decline was most likely caused by the polluted conditions of the rivers these animals call home, which produced gout-like symptoms leading to death. Breeding and restocking programs exist, but the Gharial is still in serious trouble. To find out more, check out the Gharial Conservation Alliance and the International Reptile Conservation Foundation.

Romulus Whitaker, a leading conservationist, with a young ~~Gharial~~ Australian Freshwater Croc

The 50 Most Fascinating Blogs on Fossils

2010-09-16T16:05:00.000-04:00

The word is spreading. Forgotten Archosaurs made it onto the list of The 50 Most Fascinating Blogs on Fossils on onlinecolleges.org. The blog is #12 under "Paleontology and Geology Blogs". There are a lot of other great blogs on the list, so check it out.

Jurassic Phytosaur

2010-09-03T19:34:00.000-04:00

Many of you have probably already heard, especially if you read Chinleana, that there is a paper out suggesting that at least one phytosaur - a marine phytosaur - survived into the Jurassic. I am extremely skeptical about this, but I'm aso not dismissing the idea altogether. Currently, the Jurassic (in the marine record) i defined by the first appearance of the ammonoid Psiloceras. The phytosaur discussed in this paper was found in the horizon just below the first appearance of Psiloceras, which I think makes it quite easy to conclude that the phytosaur was Late Triassic in age. But you should certainly have a read for yourself. And as we know, extinction events aren't always the most clean, abrupt events in the geologic record, so it will be interesting to see how this pans out.

Maisch, M. W. & Kapitzke, M. 2010. A presumably marine phytosaur (Reptilia: Archosauria) from the pre-planorbis beds (Hettangian) of England. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 257: 373–379. DOI: 10.1127/0077-7749/2010/0076

Don't Freak Out!

2010-08-25T12:03:00.001-04:00

This is still the same blog, I just updated the template.

Let me know what you think. Do you like the new layout? Should I go back to the old one?

Two New Neosuchians from the Mesozoic of Europe

2010-08-25T11:02:00.002-04:00

Cau, A. and F. Fanti. 2010. "The oldest known metriorhynchid crocodylian from the Middle Jurassic of North-eastern Italy: Neptunidraco ammoniticus gen. et sp. nov." Gondwana Research. DOI: 10.1016/j.gr.2010.07.007

Abstract:
Metriorhynchidae is a clade of marine-adapted crocodilians known from several Middle Jurassic–Early Cretaceous specimens collected predominantly in South America and Europe, but poorly known in the northern margin of Gondwana. The “Portomaggiore crocodile” is the most complete specimen of an Italian metriorhynchid to date: it consists of a partial skeleton that has been provisionally referred to an unnamed species of Late Jurassic Metriorhynchus or Geosaurus. The specimen is preserved in the reddish, nodular limestone of the Rosso Ammonitico Veronese Formation (Bajocian–Tithonian); new data on microfossil associations constrain the age of the metriorhynchid to the late Bajocian–earliest Bathonian. On the basis of cranial synapomorphies, the “Portomaggiore crocodile” falls as the closest sister-taxon of the Late Jurassic– Early Cretaceous geosaurines, and is referred to Neptunidraco ammoniticus gen. et sp. nov. It is unique among Middle Jurassic metriorhynchids in showing an incipient streamlining of the skull, shared with Late Jurassic and Cretaceous taxa. Since Neptunidraco is the oldest known member of Metriorhynchidae, its phylogenetic position supports the hypothesis that the timing of the initial metriorhynchid and geosaurine diversifications should start in the Bajocian.

Martin, E. J., M. Rabi, and Z. Csiki. 2010. "Survival of Theriosuchus (Mesoeucrocodylia: Atoposauridae) in a Late Cretaceous archipelago: a new species from the Maastrichtian of Romania." Naturwissenschaften. DOI: 10.1007/s00114-010-0702-y

Abstract:
Small terrestrial non-eusuchian mesoeucrocodylians are common components of Cretaceous assemblages of Gondwanan provinces with notosuchians and araripesuchids as flagship taxa in South America, Africa and Madagascar, well into the Late Cretaceous. On the other hand, these are exceedingly rare in Laurasian landmasses during the Late Cretaceous. Small terrestrial mesoeucrocodylians from Europe were often referred to the genus Theriosuchus, a taxon with stratigraphic range extending from the Late Jurassic to the late Early Cretaceous. Theriosuchus is abundantly reported from various European localities, although Asiatic and possibly North American members are also known. It has often been closely associated with the first modern crocodilians, members of the Eusuchia, because of the presence of procoelous vertebrae, a widespread key character diagnosing the Eusuchia. Nevertheless, the relationships of Theriosuchus have not been explored in detail although one species, Theriosuchus pusillus, has been extensively described and referred in numerous works. Here, we describe a new basal mesoeucrocodylian, Theriosuchus sympiestodon sp. nov. from the Maastrichtian of the Haţeg Basin, Romania, suggesting a large temporal gap (about 58 myr) in the fossil record of the genus. Inclusion of the new taxon, along with Theriosuchus guimarotae, in a phylogenetic analysis confirms its referral to the genus Theriosuchus, within a monophyletic atoposaurid clade. Although phylogenetic resolution within this clade is still poor, the new taxon appears, on morphological grounds, to be most closely related to T. pusillus. The relationships of Atoposauridae within Mesoeucrocodylia and especially to Neosuchia are discussed in light of the results of the present contribution as well as from recent work. Our results raise the possibility that Atoposauridae might not be regarded as a derived neosuchian clade anymore, although further investigation of the neosuchian interrelationships is needed. Reports of isolated teeth referable to a closely related taxon from the Upper Cretaceous of Romania and France, together with the presence of Doratodon and Ischyrochampsa, indicate a previously unsuspected diverse assemblage of non-eusuchian mesoeucrocodylians in the Late Cretaceous European archipelago.

A Little Recognition

2010-08-12T14:46:00.002-04:00

My lovely blog has just been recognized by the University of Maryland's College Park Scholars Program (CPSP) in a short news blurb. I participated in the program in my first two years at the university but stayed involved for all four years of my undergraduate career.

I certainly do credit Drs. Holtz and Merck for my knowledge of Crurotarsans and website development (even though blogger.com does most of the work as far as the website itself, I can do a lot more with my knowledge of html code). I am well known for my my praise of Dr. Merck, Dr. Holtz, and the Earth, Life, & Time program (example), so I wont start again here, but the College Park Scholars Program deserves a lot of credit too for the quality it adds to both life and education at the University of Maryland. So thanks CPSP!!! Keep up the good work and your students will follow.

Dr. Merck (left) and Dr. Holtz (right)

Crocs in the News

2010-08-11T15:29:00.000-04:00

Hope for the Future of Crurotarsan Archosaurs:
2600 Baby Saltwater Crocodiles Born

No Death Roll for these Crocs:
Ancient Crocs May Have Chewed Like Mammals

Pakasuchus kapilimai

Pristichampsus

2010-07-18T20:23:00.001-04:00

Alright, breaking out of the Triassic, and clear into the Cenozoic, I'm back with Pristichampsus:

Pristichampsus illustrated by Robert Bakker

Meaning: "saw crocodile"

Species: P. hengdongensis and P. rollinati (after Rossmann 1998)

Nominal Author: Gervais 1853

Age: Paleocene and Eocene

Location: Asia, Europe, and North America

Physical Characteristics: approx. 3 meters long, carnivorous eusuchian with long limbs (cursorial, capable of galloping and facultative bipedalism) and a round tail

Paleobiogeography

The genus Pristichampsus originated in Asia and later spread to the rest of the northern hemisphere. P. hengdongensis (Li, 1984) is known from the Paleocene through Middle Eocene of China and the Middle Eocene of India. P. rollinati (Gray 1831) is known from the Late Paleocene of China, the Early and Middle Eocene of North America, and the Middle and Late Eocene of Europe (Germany, Italy, and France). There are two possibilities in the dispersion of Pristichampsus: either the species spread directly to Europe from Asia, or to Europe through North America from Asia (Kotsakis et al 2004).

A lil' somethin' funny while I work on a REAL post

2010-07-11T14:37:00.001-04:00

From icanhascheezburger.com

SVP

2010-07-07T12:28:00.001-04:00

This is just a reminder: today is the last day to get the early registration rate and it is the deadline for field trip and workshop registration for the 70th Annual Meeting of the Society of Vertebrate Paleontology. So hurry over to the website and get yourself registered. Regular rregistration last through September 8th. The meeting will be held October 10 - 13 at the David L. Lawrence Convention Center & Westin Convention Center in Pittsburgh, PA, USA. Hope to see you there! Also note: I've posted a poll for SVP attendance.

P.S. I promise to get back to posts of higher quality very soon. Honestly.

Typothorax

2010-06-27T20:24:00.001-04:00

Sorry for the long hiatus, but you all know how busy life can get. I'm back though, with a post on Typothorax.

(from the cover of JVP, Volume 30, Number 3. By Matthew Celeskey)

Meaning: "mark made by a blow to the breastplate"

Species: T. coccinarium (Cope 1875), T. antiquum (Lucas et al 2002)
Nominal Author: Cope 1875
Age: Late Triassic
Location: North America - Arizona (Chinle Formation), New Mexico and Texas (Bull Canyon Formation, Dockum Group)
Physical Characteristics: no more than 3 meters in length, with a tail equalling approximately half the body length and a mass of about 100 kg. Typothorax possessed the typical aetosaur armor with enlarged spike on its neck.

A Call for Feet

2010-05-25T12:43:00.001-04:00

I'm taking a break this week from my featured species post because life is just too busy. In the mean time, I would like to ask for a little help from you all. I am looking for a good picture of the full, articulated foot and ankle of a crurotarsan. If anyone has a good picture, a paper with a good picture or schematic, or access to a specimen that they can photograph, I would greatly appreciate it if you would contact me. I am an artist in my spare time and as such, I would like to create a logo for the blog (and what better logo than a crurotarsan ankle), but the scientist in me wants to get it as accurate as possible.

Also, there have been several more articles popping up about the Prestosuchus recently found in Brazil. It is the first specimen found with a well preserved hind leg, which should give a lot of insights into how this animal moved and it's phylogenetic relationship to other rauisuchians. The fossil was found in a formation that was once a lake, which may give us some clues as to how Prestosuchus lived.

Lastly, I just got my first mailing about the 70th annual meeting of the Society of Vertebrate Paleontologists. The meeting will be held in Pittsburgh, Pennsylvania, USA at the Westin Convention Center, October 10th through 13th and is hosted by the Carnegie Museum of Natural History. I hope to see you all there!

Geosaurus

2010-05-19T13:34:00.004-04:00

Type of Geosaurus giganteus (Von Sommerring 1816)(from Young and Andrade 2009)

(sensu Yound and Andrade 2009)
Meaning: "earth lizard"
Species: G. giganteus (type - von Sommerring 1816 as Lacerta giganteus), G. grandis (Wagner 1858), G. lapparenti (Debelmas and Strannoloubsky 1957), G. carpenteri (Wilkinson et al 2008)
Nominal Author: Cuvier 1824
Age: Late Jurassic to Early Cretaceous
Location: Europe (incl. UK and Germany)
Physical Characteristics: a short snouted marine crocodyliform (thalattosuchia)

A Major Revamp of the Genus:
In 2009, Young and Andrade redescribed the type species Geosaurus giganteus and reassessed the genus, butting to an end the "Fraas Misconception" which had resulted in the inclusion of longirostrine species to the genus. Four species, G. vignaudi (Frey at al 2002), G. saltillense (Buchy et all 2006), G. suevicus (Fraas 1901), and G. araucanensis (Gaspirini and Dellape 1976) were renamed as members of the genus Cricocosaurus (bootstrap=67). Rhacheosaurus gracilis Wagner 1852 (renamed Geosaurus gracilis by Fraas 1902) was reestablished. Young and Andrade consider Geosaurus to then be composed of three species sensu stricto (G. giganteus, G. grandis, and G. lapparenti [formerly Dakosaurus lapparenti Steel 1973] bootstrap=50) but also propose G. carpenteri (formerly D. carpenteri Wilkinson et al 2008) and the 'croccodrillo di Portomaggiore' (Leonardi 1956 - still awaiting proper description) as members of the genus (bootstrap=51). Their phylogenetic analysis resulted in a strict consensus of 4104 most parsimonious trees (tree length=578, CI=0.436, RI=0.861, RC=0.376).

Morphology:
Little postcranial material exists for Geosaurus, but based on the available material, it is clear that Geosaurus was adapted to a fully pelagic lifestyle with a streamlined skull and flattened humeri. Proportionally, Geosaurus giganteus has one of the shortest rostra among thalattosuchians and the snouts of other species of Geosaurus are similarly brevirostrine or mesorostrine (Young and Andrade 2009). Its cranial bone as are smooth and lack ornamentation. Geosaurus also has one of the most robust, well developed sclerotic ring (second only to C. schroderi) which encompasses the entire orbit. The teeth of Geosaurus are arranged as opposing blades that are serrated and strongly lateromedially compressed (Young and Andrade 2009). Some general metriorhynchid characteristics include hydrofoil-like forelimbs and a hypocercal tail, convergent with many other Mesozoic marine reptiles. There is also evidence for salt glands as a means of osmoregulation (Fernandez and Gasparini 2008).

Life and Ecology:
Metriorhynchids are the only group of archosaurs to ever fully adapt to life in the marine realm (Steel 1973) and are thought to be stalking predators that fed on fast-moving fish and cephalopods (Hua 1994). Geosaurus is endemic to Europe, with species living from the Late Jurassic (Oxfordian), when they (along with Dakosaurus) replaced medium-sized pliosaurs and Suchodus (Young pres. observ./ Young et al 2010) to the Early Cretaceous (Valangian) when all metriorhynchids went extinct. Geosaurus evolved over time to become more streamlined and hypercarnivorous as it was more able to sustain fast swimming speeds for longer periods and to efficiently slice through fleshy prey (Young et al 2010, Massare 1988). The nature of their sclerotic ring suggests that species of Geosaurus may have even occasionally ventured on deep dives (Young and Andrade 2009).

No Love for the Paleogene

2010-05-14T18:54:00.000-04:00

The results for the second poll are in. So, which Crurotarsan time period was your favorite? No surprise, it was the Triassic. But the rest of the results were a little more interesting. In second place was the Cretaceous Period (which I am going to somehow blame on Tom Holtz). Really surprising was the time period in 3rd place, which wasn't actually a period, but an era, and it wasn't even a Crurotarsan era. It was the Paleozoic! I'm just wondering, who comes to a Crurotarsan themed blog and votes in a poll for an option that starts with the phrase "screw Crurotarsans"? Well, we're glad you're here anyway, even if we're not sure why. The Jurassic came in 4th place with a measly 5%. Tied for 5th were the Neogene and anything-but-the-Phanerozoic (same question to these people: you do realize this is a blog about critters from the Phanerozoic?). And for whatever reason, the Paleogene got no votes. NONE! Nada. Niet.

Well, I'm pretty perplexed at some of you, but as I said, I'm glad to have you anyway. Stay tuned for more polls and more hot Crurotarsan action!

Nearly Complete Prestosuchus Found

2010-05-12T14:51:00.003-04:00

I got the word yesterday from Marcel Lacerda of the Universidade Federal do Rio Grande do Sul, Instituto de Geociências, that a nearly complete skeleton of Prestosuchus has recently been found in southern Brazil. You can read the original article (in Portuguese) here, or, I have made my attempt at translating it into English below.

"Brazilian researchers found the fossil of a prehistoric predator in excellent condition near a town 260 km from Porto Alegre. A reptile, classified as Prestosuchus chiniquensis, lived 240 million years ago, before the appearance of the dinosaurs. It is the most well preserved fossil of the major predator of the Middle Triassic. A paleontologist of the Universidade Luterana do Brasil (Ulbra) Sergio Cabreira and a biologist, Lucio Roberto da Silva combed a ravine where two fossil vertebrae had already been found; they then saw the should blade of a Prestosuchus recently uncovered by the rains. After they removed some of the sediment, they uncovered parts of the skull, forearms, and chest.

Prestosuchus belonged to a group of basal archosaurs - predators that preceded the dinosaurs, pterosaurs, and crocodiles in the tree of evolution. Morphologically, the fossil is more similar to an alligator; it walked on all fours, had a long tail, and a long snout. But it walked upright. Researchers estimate that it weighed 1 ton and was about 7 meters long and 1.5 meters tall."

Not the most scientific of articles (especially the part about Prestosuchus living BEFORE dinosaurs appeared), but a good briefing on such a recent discovery. Prestosuchus is probably my favorite extinct animal (and I'm guessing you're all fans as well), so it will be very exciting to see this develop. Would you just look at that beautiful skeleton!

Thank you Marcel! I hope my translation was fairly accurate.

Also, don't forget to cast your vote for your favorite Crurotarsan time period! The poll closes early Friday morning.

Arizonasaurus

2010-05-10T18:26:00.002-04:00

Arizonasaurus babbitti. Scale bar = 0.5 meters. (Nesbitt 2005)

Meaning: "Arizona lizard"
Species: A. babbitti
Nominal Author: Welles 1947
Age: early Middle Triassic (Anisian - 240 Ma)
Location: Arizona, southwestern USA (Moenkopi Formation)
Physical Characteristics: a large (3+ meters) sail-backed predator (Rauisuchian)

Significance:
Arizonasaurus was the dominant predator of the Moenkopi fauna, which represented an important transition into a modern fauna of crocodiles, dinosaurs(birds), mammals, lizards, and turtles, as opposed to the previous fauna, dominated by more primitive tetrapods (Nesbitt 2003). Arizonasaurus helps to close the gap between the primitive fauna of the Lower Triassic and the more modern fauna of the Upper Triassic. The type specimen for Arizonasaurus consisted solely of a mostly complete left maxilla (Welles 1947), but the far more complete skeleton found by Nesbitt in 2002 has helped to resolve relationships between fragmentary and more complete taxa within Rauisuchia.

Rauisuchian Phylogenetics:
The holotype of Arizonasaurus babbitti has been considered a dinosaur, a stagonolepid, a rauisuchian, a proterosuchian, a trilophosaurid, and a erythrosuchid, but the new remains discovered by Nesbitt suggest that Arizonasaurus is indeed a poposaurid (Hunt 1993, Nesbitt 2003). A more recent archosaur phylogeny places Arizonasaurus within Poposauroidea (bootstrap <50/4) which, combined with its sister taxon Rauisuchoidea, makes up Rauisuchia (Brusatte et al 2010). Within Poposauroidea, resolution decreases, resulting in a polytomy between Arizonasaurus, Bromsgroveia, Lotosaurus, Poposaurus, Sillosuchus, and Shuvosauridae (Effigia + Shuvosaurus). When ankle characters were removed, Arizonasaurus and Bromsgroveia were united into a single taxon.

And the winner is...

2010-05-07T09:27:00.003-04:00

The poll for "which name do you prefer?" is closed and the results are in. Crurotarsi wins by a landslide with 72% of the votes, followed up by Pseudosuchia with a modest 22%, and Crocodylotarsi with a mere 6%. Obviously, this doesn't resolve any of the issues in the nomenclature, but it gives me a nice view of the readership. Surely, these results are biased. How many people who dislike the term "Crurotarsi" are going to come to a blog with such a name in the title? But clearly there are enough, since 28% of the votes were anti-Crurotarsi. Although the results of this poll may show a bias, I feel a review of the literature may reveal similar skewing in favor of "Crurotarsi", but we shall see.

In other news, I arrived home on Wednesday, after a Cinco de Mayo get together with 2 of my favorite Paleontologists, to a wonderful sight. In my front hallway was a book-shaped package from Amazon and inside was my copy of Triassic Life on Land: The Great Transition by H-D Seus and Nicholas Fraser.

It came out at the end of last month and I have been dying to get my hands on a copy. I have only had the time to browse through it, but it looks pretty Trias-tastic. It is definitely more technical than Fraser's previous book Dawn of the Dinosaurs: Life in the Triassic, without all the pretty paintings by Douglas Henderson, but with the benefit of more up-to-date information.

FYI, if any of you buy one of the above books (or any Amazon product linked to on this website, like on the Resources page) from a link on this website, I get a small portion of the sale. So start buying some Triassic literature and support your favorite crurotarsan-themed blog!

Rutiodon

2010-05-04T21:40:00.002-04:00

Meaning: "wrinkle tooth"
Species: R. carolinensis, R. manhattanensis (?)
Nominal Author: Emmons 1856
Age: Middle Carnian (Triassic)
Location: Eastern US (North Carolina, possibly New Jersey and Pennsylvania)
Physical Characteristics: Piscivorous phytosaur of 3 to 8 meters in length with a gavial-like long, slender snout. Skull can be identified by slight posterior depression of the supratemporal fenestra and homodont dentition. Nares are positioned at the highest point on the skull.

Rutiodon carolinensis Emmons 1856. A.M.N.H. No. 1 composite skeleton of material collected in North Carolina. From Colbert 1947.

History and Validity
Although it is one of the oldest and most familiar of the phytosaurs, Rutiodon has struggled as a solid, valid taxon. Since Rutiodon was erected in 1856, numerous species have been added to and subtracted from the genus and its validity has been questioned. Emmons name the type species, R. carolinensis, from the Cumnock Formation (Sanford Basin, Newark Supergroup) o North Carolina. Rutiodon manhattanensis was then found in another basin of the Newark Supergroup by Huene (1913) in New Jersey. In 1922, Case added R. crosbiensis from the southwestern US. Another two species from the southwest, R. gregorii and R. adamanensis, were named by Camp (). However, the three southwest species were later found to be members of the genus Leptosuchus and R. manhattanensis is now considered nondiagnostic due to insufficient material (Doyle and Seus 1995). Therefore, the genus can be restricted to R. carolinensis (Long and Murry 1995). The validity of the type specimen itself has been questioned, but was upheld by Hungerbuhler and Sues in 2001 (who also believed it to be valid in the southwestern as well as the eastern US).

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So yeah, this is a pretty problematic taxon and since I'm not too familiar with phytosaurs (Rauisuchians are more my style) I did not know to expect so many issues in the literature when I chose Rutiodon as the feature for the week (hence the late post). I think next week I'll step outside of the Triassic to see if I can get a better understood genus.

By the way...

2010-04-30T14:11:00.000-04:00

I don't know about you, but I love the Arbor Day Foundation. Now, there is the Mach`s Grün! effort, which has the Arbor Day Foundation plant a tree in Plumas National Forest in Northern California whenever someone posts the above link on their blog or website. I'm all about helping the environment, especially forests, and while I'd prefer to put more money into protecting existing forests, planting new trees is an excellent cause as well.

In other news, you may have noticed that I finished the post on Desmatosuchus, added a poll, and added an About page. If you haven't, check them out!

Desmatosuchus

2010-04-25T21:01:00.012-04:00

Meaning: "link crocodile"

Species: "D." haplocerus, D. spurensis, and D. smalli

Nominal Author: Case 1920

Age: Carnian(?)/ Norian (Late Triassic)

Location: Southwestern US (Texas, New Mexico, Arizona - Chinle and Dockum strata)

Physical Characteristics: Large (4+ meters) aetosaur. Typical aetosaur characteristics include an armored carapce arranged in four columns along the dorsal side, an upturned “pig-nosed” premaxilla, and stout forelimbs. Desmatosuchus is distinct in having large recurved spines on the posterior part of its neck.

D. haplocers skull (from Small 2002) but probably actually D. smalli (Parker)

Ecology

Aetosaurs have long been considered herbivorous, using their skulls and stout forelimbs to dig for soft vegetation and roots, and possibly even insects (Walker 1961). Some parallels can be drawn between aetosaurs and armadillos, due to several convergent characteristics, that may shed light on how aetosaurs fed (Small 2002). Armadillos are considered generalists, but feed predominately on insects and grubs found by digging in the dirt. Such food sources were indeed available for aetosaurs in the Late Triassic. Nests and burrows of various social insects (bees, wasps, termites) have been found in throughout Triassic strata and even fossil wood (Hasiotis, Dubiel, and Demko 1995; Hasiotis and Dubiel 1995). The teeth of Desmatosuchus seem to share characteristics with both herbivorous dinosaurs as well as carnivorous archosaurs (Small 2002). In fact, there may have even been a carnivorous aetosaur living in the Triassic (Murry and Long 1996). All these factors support the possibility of insectivory and/or omnivory among at least some aetosaurs, including Desmatosuchus.

(Personally, I really like the aetosaur/armadillo comparison. And I mean, they even live in the same place! Coincident? I think not!)

Termite burrows (circled in blue) in a siltstone from the Newark Supergroup of Maryland. Picture by Susan Drymala.

The geology of the formations in which Desmatosuchus is found suggests that this animal spent at least some of its time in the floodplains of rivers in ancient Texas, New Mexico, and Arizona (Small 2002; Parker 2008). The rich soils would have supported the insects that have been suggested as the mainstay of the aetosaur diet (Small 2002). Other local inhabitants would have included rauisuchians like Postosuchus and Chatterjeea, other aetosaurs like Paratypothorax and Typothorax, small metaposaurids and other temnospondyls, Arribasuchus and Leptosuchus (phytosaurs), Technosaurus (a dinosaur), and several other taxa including Shuvosaurus and Protoavis (Small 2002; Parker 2008).

Desmatosuchus encounters Postosuchus. Artwork by Douglas Henderson in Dawn of the Dinosaurs: Life in the Triassic by Nicholas Fraser (Plate 7.5A)

Taxonomy
The first material of what we now call Desmatosuchus was described by Cope in 1892 and named Episcoposaurus haplocerus. In 1920, Case first described Desmatosuchus spurensis, which, like E. haplocerus, was considered a phytosaur at the time. Gregory (1953) later revised the taxonomy of Cope and Case, giving us D. spurensis and D. haplocerus as the soul species of Desmatosuchus.

During the last decade or so, there has been a lot of work done on the systematic paleontology of Desmatosuchus. In 2005, Bill Parker erected a new species to the genus, D. smalli. Parker also demonstrated that “D.” chamaensis (Zeigler et al 2002) is more closely related to Paratypothorax than to Desmatosuchus, representing a different genus (2008). Heckert and Lucas (1999) have suggested that Acaenasuchus geoffreyi Long and Murry is a juvenile Desmatosuchus, but Parker cast doubt on this, citing our poor understanding of aetosaur ontogeny and insufficient morphological characters used to refer Acaenasuchus to Desmatosuchus. Finally, because D. haplocerus was found to be nondiagnostic at the species level, we are left with only two valid species: D. spuensis and D. smalli (Parker 2008).

In Popular Culture:

Desmatosuchus has been featured on several TV programs, including Animal Armageddon: Target - Earth and When Dinosaurs Roamed America. There is even a toy Desmatosuchus floating around out there.

In loving memory of Steve Yang.

Feb. 11, 1985 - April 21, 2010

In Honor of Earth Day

2010-04-22T07:39:00.000-04:00

Since it's earth day, I thought I would talk about an extant species of Crurotarsi, the America alligator (Alligator mississipiensis), and its importance to the everglades ecosystem.

The American alligator is considered a keystone species, meaning that it plays a vital role in its ecosystem (and can be used as an indicator of that ecosystem's health). The major contribution of the alligator is its "gator hole". Alligators dig their holes as refuges during the dry season, but these hole don't just serve the alligator. The gator holes are vital sources of water for fish, birds, turtles, and many other species, and they end up being a convenient source of food for the alligators. Alligators also provide a service through the building of their nests. Several turtle species rely on these nests to lay their own eggs.

The American alligator was put on the endangered species list in 1967. They were killed for their skin and also because they were considered a nuisance. However, after laws were passed to protect the alligators, they rebounded and were removed from the endangered species list in 1987.

Everglades NP - The American Alligator in Depth
The Keystone Species Concept

1 week and counting.

2010-04-21T08:57:00.000-04:00

So, yesterday marked 1 week for this blog and I am pretty pleased with the way things have been going. We've had visitors from over 12 states, 8 countries, and 4 continents! On that note, there are just a few people I want to thank for helping to get this blog going. First, David Tana over at Superoceras for inspiring me to start the blog. Second, Dr. Tom Holtz for first getting the word out on facebook. And last but not least, Bill Parker for spreading the word on his blog Chinleana. Thanks everyone!

As I have mentioned, I will be posting a weekly feature on a particular species each week (Prestosuchus was the first), but I will also intersperse posts about other issues surrounding Crurotarsi. I have been slowly adding to the Pictures and Resources pages. I am also working on an About page, and if I see there is a need, I will include some sort of glossary type page to explain some of the more technical paleo-lingo for the novice.

It's only been a week, so bear with me as the blog grows and evolves. I think we're off to a good start, but there's much more to come.

Prestosuchus

2010-04-18T16:24:00.003-04:00

Meaning: "Presto's Crocodile"
Species: P. chiniquensis and P. loricatus
Nominal Author: Huene 1942
Age: Ladinian - Carnian (Middle/Late Triassic)
Location: Santa Maria Formation, Brazil
Physical Characteristics: Large (~5 meters) quadrupedal predator with an erect posture

Taxonomy
Prestosuchus was originally described by Friedrich von Huene in 1942 as two different species: P. chiniquensis and P. loricatus. However, because of the amount of material and Huene's failure to designate holotype specimens, Prestosuchus taxonomy has been problematic. Krebs (1976) has suggested that the two Prestosuchus species are in fact synonymous and Barberena (1978) presented a specimen as being the skull of Prestosuchus. Brusatte et al (2010) have recently concluded that if the Barberena skull and the Huene material do indeed represent different taxa, then they are at least very closely related. A detailed revision of Prestosuchus taxonomy is currently being performed by Julia B. Desojo.

Phylogeny
Prestosuchan (and Rauisuchan, for that matter) phylogenetics has been extremely problematic. Fortunately, a recent study by Brusatte et al (2010) seems to have sorted things out. Prestosuchus and Batrachotomus have been shown to compose a sister taxon pair with an 81% bootstrap value. Prestosuchidae Romer 1966 is described the most inclusive clade containing Prestosuchus chiniquensis Huene 1942 but not Rauisuchus tiradentes Huene 1942. By the Brusatte phylogeny, Prestosuchidae therefore consists of Prestosuchus, Batrachotomus, and Saurosuchus. Moving out further in the phylogeny, we get Rauisuchoidea which includes Prestosuchidae plus Rauisuchidae and a basal cluster which includes Ticinosaurus. Finally, we see a monophyletic Rauisuchia made up of Rauisuchoidea and Poposauroidea.

This is the first in a series of weekly posts I will be making. Every Sunday, I will feature an overview of a Crurotarsan species (or genus for that matter). I will mostly choose at random but requests are welcome.

CAMP and the Triassic-Jurassic Extinction

2010-04-15T09:39:00.003-04:00

A new paper published in the Proceedings of the National Academy of Sciences this week (online as of March 22) suggests that it was indeed the volcanism associated with CAMP (the Central Atlantic Magmatic Province) that was directly responsible for the end-Triassic extinction (and therefor, the extinction of many major groups of Crurotarsans). The findings show that the carbon isotope excursion (CIE) of the extinction occured simultaneously with the erruption of CAMP. The close relationship between the extinction, the eruptions, and the CIE is the strongest evidence yet presented for a volcanic cause for the Triassic-Jurassic extinction. Below, I list two news articles that discuss the paper. The full citation for the paper can be found on the resources page of this site.

Wired: Dinosaurs Rode Volcanic Armageddon to Victory
Discovery News: How Dinos Ruled The World

Gotta Love Taxonomy

2010-04-14T17:25:00.002-04:00

I came across this (The 10 Lamest Dinosaur Names) and just wanted to thank Crurotarsan paleontologists for not getting too carried away in the naming of their discoveries.

But there is one Rauisuchian that I have to make fun of a little:

Poposaurus

"Oh hell no! Here come da poposaurus! Stash the dope, yo!"

A Few Notes While I Get Myself Organized

2010-04-14T15:19:00.000-04:00

As many of you know, there is a lot of information out there on Crurotarsans, so as I begin to wade through all that, I'd just like to say a few things.

As you may have noticed, I have added a page for pictures and a page for resources (academic papers, books, etc). They are in their very early stages of development, so bear with me, and if you wish to contribute, feel free.

Just a warning: the majority of my posts will focus on the Triassic representatives of our starring clade. Afterall, the Triassic was when they were at their most numerous and diverse. But for those of you who prefer the post-Triassic crocs, you will not be forgotten. I could never leave out such cool critters like Thalattosuchia and Pristichampsus.

I plan on having a few weekly or monthly themed posts. For instance "The Weekly Crurotarsan" where I feature a single species. I'm not sure about the title, but you get the idea. "Crurotarsan" doesn't always flow off the tounge so nicely. I tend to trip over the 'r's myself. But what would replace it? "Crurotarsan" doesn't lend itself to a nickname very easlily, unlike say "Dinosaur" which is so readily shortend to "dino". I could always use "croc", but I feel like that should be reserved strictly for Crocodylomorphs... but I digress.

Just sit back, relax, and prepare yourselves for some awesome extinct archosaur action.

Welcome. An Intro to Crurotarsi.

2010-04-13T13:22:00.006-04:00

Hi everybody!

I present, as my first entry, a brief introduction to the great clade, Crurotarsi.

Crurotarsans are some pretty amazing animals, having occupied almost every major ecological niche during the Triassic Period, a time that lasted almost 50 million years (251 Ma to 201.6 Ma). They still survive today as crocodiles, alligators, and their relatives but are nowhere near as diverse and impressive as their ancestors. Named by Paul Sereno in 1991, Crurotarsi means "cross-ankles" based on the way their ankles articulate compared to their sister taxon, Avemetatarsalia (Dinosaurs, Pterosaurs, etc). Although the taxonomy is still disputed some of the groups that make up this clade include Phytosaurs, Aetosaurs, Rauisuchians, Poposaurids, and Crocodylomorphs.