Journal of Vertebrate Paleontology e1794885 (26 pages) This work was authored as part of Adam D. Marsh, Matthew E. Smith and William G. Parker’sofficial duties as Employees of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law. Randall B. Irmis and Ben T. Kligman hereby waive their right to assert copyright, but not their right to be named as co-authors in the article. DOI: 10.1080/02724634.2020.1794885 ARTICLE SKELETAL ANATOMY OF ACAENASUCHUS GEOFFREYI LONG AND MURRY, 1995 (ARCHOSAURIA: PSEUDOSUCHIA) AND ITS IMPLICATIONS FOR THE ORIGIN OF THE AETOSAURIAN CARAPACE ADAM D. MARSH, *,1 MATTHEW E. SMITH,1 WILLIAM G. PARKER, 1 RANDALL B. IRMIS,2 and BEN T. KLIGMAN 3 1Petrified Forest National Park, Division of Science and Resource Management, Arizona 86028, U.S.A.,
[email protected];
[email protected];
[email protected]; 2Natural History Museum of Utah and Department of Geology & Geophysics, University of Utah, Salt Lake City, Utah 84108-1214, U.S.A.,
[email protected]; 3Virginia Tech, Department of Geosciences, Blacksburg, Virginia 24061, U.S.A.,
[email protected] ABSTRACT—Acaenasuchus geoffreyi is a diminutive armored archosaur from the Upper Triassic Chinle Formation of northern Arizona, U.S.A., with uncertain evolutionary relationships and skeletal maturity. Known only from osteoderms, the taxon has been considered a valid taxon of aetosaur, juvenile specimens synonymous with the aetosaur Desmatosuchus spurensis, or a non-aetosaurian pseudosuchian archosaur. Here, we describe new fossils of Acaenasuchus geoffreyi that represent cranial, vertebral, and appendicular elements as well as previously unknown variations in the dorsal carapace and ventral shield.