Friday, December 3, 2010

Baurusuchus

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


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