On the validity and phylogenetic position of Eubrachiosaurus browni, a kannemeyeriiform dicynodont (Anomodontia) from Triassic North America

PLoS One. 2013 May 31;8(5):e64203. doi: 10.1371/journal.pone.0064203. Print 2013.

Abstract

The large dicynodont Eubrachiosaurus browni from the Upper Triassic Popo Agie Formation of Wyoming is redescribed. Eubrachiosaurus is a valid taxon that differs from Placerias hesternus, with which it was previously synonymized, by greater anteroposterior expansion of the scapula dorsally and a very large, nearly rectangular humeral ectepicondyle with a broad supinator process. Inclusion of Eubrachiosaurus in a revised phylogenetic analysis of anomodont therapsids indicates that it is a stahleckeriid closely related to the South American genera Ischigualastia and Jachaleria. The recognition of Eubrachiosaurus as a distinct lineage of North American dicynodonts, combined with other recent discoveries in the eastern USA and Europe, alters our perception of Late Triassic dicynodont diversity in the northern hemisphere. Rather than being isolated relicts in previously therapsid-dominated regions, Late Triassic stahleckeriid dicynodonts were continuing to disperse and diversify, even in areas like western North America that were otherwise uninhabited by coeval therapsids (i.e., cynodonts).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animal Distribution
  • Animals
  • Biological Evolution
  • Bone and Bones / anatomy & histology*
  • Bone and Bones / physiology
  • Dinosaurs / anatomy & histology
  • Dinosaurs / classification*
  • Dinosaurs / physiology
  • Europe
  • Female
  • Fossils
  • Male
  • Phylogeny*
  • Phylogeography
  • Wyoming

Grant support

Research by CFK and JF was supported by the Deutsche Forschungsgemeinschaft (FR 2457/3-1 and FR 2457/4-1) and a Sofja Kovalevskaja-Award of the Alexander von Humboldt Foundation and the Federal Ministry of Education and Research to JF. Research by KDA was supported by the Department of Geology of the Field Museum of Natural History. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.