Field of Science

Two New Early Archosaur Papers

These are the last two articles from the forthcoming volume titled "Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin". The book should be available for purchase soon from the Geological Society of London.

Liparini, A., and C. L. Schultz. 2013. A reconstruction of the thigh musculature of the extinct pseudosuchian Prestosuchus chiniquensis from the Dinodontosaurus Assemblage Zone (Middle Triassic Epoch), Santa Maria 1 Sequence, southern Brazil. From Nesbitt, S. J., Desojo, J. B. & Irmis, R. B. (eds) Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379. 

Abstract - Prestosuchus chiniquensis is an extinct species of terrestrial archosaur from the Middle Triassic Epoch restricted to southern Brazil. In this paper the thigh musculature of P. chiniquensis is reconstructed based on a well-preserved specimen and on myological descriptions of extant birds and crocodylians. Among the 16 analysed muscular groups, 13 were recognized as present and homologous to both extant groups of archosaurs, and two only to the crocodylian line of archosaurs, so that 15 muscular groups were reconstructed in the fossil specimen. Morphological particularities of the pelvic girdle and the hindlimbs of P. chiniquensis gave a distinct arrangement for the muscular origin and insertion sites, leading to different lines of action and functions when compared with extant archosaurs. The comparison between extinct and extant archosaurs showed a basal condition sustained in some aspects, such as the morphology of the femur and the flexion of the knee, although other aspects were considered as derived, such as the morphology of the pubis and ischium, and their associated muscle origin locations.

Raugust, T., Lacerda, M., and C. L. Schultz. 2013. The first occurrence of Chanaresuchus bonapartei Romer 1971 (Archosauriformes, Proterochampsia) of the Middle Triassic of Brazil from the Santacruzodon Assemblage Zone, Santa Maria Formation (Paraná Basin). From Nesbitt, S. J., Desojo, J. B. & Irmis, R. B. (eds) Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379.

Abstract - Proterochampsians are basal archosauriforms whose record is restricted to the Middle and Upper Triassic in Argentina and Brazil. They are quadruped forms that present characteristics consistent with a semi-aquatic lifestyle, such as an anteroposteriorly elongated skull that is flattened dorsoventrally with dorsally located orbits. In 2003, specimen UFRGS-PV-0877-T was discovered at the Schoenstadt site, in the city of Santa Cruz do Sul (Santacruzodon Assemblage Zone, Santa Maria Formation). This specimen, consisting of disarticulated cranial elements (such as nasals, frontals, parietals, postorbitals, a left squamosal, a left pterygoid and a fragment of a right mandibular ramus that bears teeth) and postcranial elements (such as femora, the left tibia, one vertebral centrum and two rib fragments), is assigned to the ‘proterochampsian’ Chanaresuchus bonapartei Romer (1971). This assignment is based on the shared V-shaped frontal-parietal suture of the new specimen and Chanaresuchus bonapartei, which differs from the transversely aligned and zigzagged pattern of C. ischigualastensis.

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