Thursday, January 19, 2012

A New Aetosaur

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

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.

Friday, January 13, 2012

First Symposium on the Evolution of Crocodyliforms

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.

Thursday, January 12, 2012

New Jersey Borealosuchus

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

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.