Osteology of Pseudochampsa ischigualastensis gen. et comb. nov. (Archosauriformes: Proterochampsidae) from the early late triassic ischigualasto formation of Northwestern Argentina

PLoS One. 2014 Nov 26;9(11):e111388. doi: 10.1371/journal.pone.0111388. eCollection 2014.

Abstract

Proterochampsids are crocodile-like, probably semi-aquatic, quadrupedal archosauriforms characterized by an elongated and dorsoventrally low skull. The group is endemic from the Middle-Late Triassic of South America. The most recently erected proterochampsid species is "Chanaresuchus ischigualastensis", based on a single, fairly complete skeleton from the early Late Triassic Ischigualasto Formation of northwestern Argentina. We describe here in detail the non-braincase cranial and postcranial anatomy of this species and revisit its taxonomy and phylogenetic relationships. The phylogenetic analysis recovered 'Chanaresuchus ischigualastensis' as part of a trichotomy together with Gualosuchus reigi and Chanaresuchus bonapartei. Accordingly, "Chanaresuchus ischigualastensis" can be potentially more closely related to Gualosuchus reigi, or even Rhadinosuchus gracilis, than to Chanaresuchus bonapartei. In addition, after discussing previously claimed synapomorphies of Chanaresuchus, we could not find unambiguous support for the monophyly of the genus. As a result, we propose here the erection of the new genus Pseudochampsa for 'Chanaresuchus ischigualastensis', which results in the new combination Pseudochampsa ischigualastensis. The information provided here about the anatomy and taxonomy of Pseudochampsa ischiguaslastensis will be useful for future quantitative analyses focused on the biogeography and macroevolutionary history of proterochampsids.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Argentina
  • Bones of Lower Extremity / anatomy & histology
  • Bones of Lower Extremity / physiology
  • Bones of Upper Extremity / anatomy & histology
  • Bones of Upper Extremity / physiology
  • Dinosaurs / anatomy & histology*
  • Dinosaurs / classification
  • Dinosaurs / physiology
  • Extinction, Biological
  • Fossils*
  • Osteology
  • Phylogeny*
  • Skull / anatomy & histology*
  • Skull / physiology
  • Spine / anatomy & histology
  • Spine / physiology
  • Thorax / anatomy & histology
  • Thorax / physiology

Grants and funding

MDE is supported by a grant of the DFG Emmy Noether Programme to Richard Butler (BU 2587/3-1). MJT is supported by a grant of the Agencia Nacional de Promoción Científica y Técnica (PICT 2012-0741) and Universidad de San Juan (UNSJ 22/13-CS). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.