DESOJO Julia Brenda
New Specimen Sheds Light on the Anatomy and Taxonomy of the Early Late Triassic Dinosauriforms from the Chañares Formation, NW Argentina
EZCURRA, MARTÍN D.; NESBITT, STERLING; FIORELLI, LUCAS E.; DESOJO, JULIA B.
ANATOMICAL RECORD-ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY
WILEY-LISS, DIV JOHN WILEY & SONS INC
The lower Carnian levels of the Chañares Formation (IschigualastoVilla Unión Basin, La Rioja Province) have yielded some of the most informative dinosaur precursor species known so far. However, these speciesare based on partial skeletons that in several cases hamper the comparisonbetween them because of the absence of overlapping bones. This has generated a contentious debate during the last 20 years about the synonymybetween two of these species, Lewisuchus admixtus and Pseudolagosuchusmajor. Here, we describe a new dinosauriform partial skeleton (CRILARPv 552) recently collected in the Chañares Formation that preserves previously unknown anatomical regions for the dinosaur precursors of this unit(e.g., premaxilla, inner ear, anterior zeugopodium) and allows comparisonswith other dinosauriform specimens. CRILAR-Pv 552 is referred toLewisuchus admixtus because it possesses a proportionally large skull, alaterally projected, shelf-like ridge on the jugal, and recurved, finely serrated middle?posterior maxillary and dentary teeth ankylosed to the bone,and the absence of a coracoid foramen. The new specimen preserves a dorsally bowed dentary with a lateroventral shelf that is identical to a dentaryassociated with the holotype of Lewisuchus admixtus. Additionally, themorphology of the new specimen is completely congruent with that of specimens of Pseudolagosuchus major, bolstering the hypothesis that the latterspecies is a subjective junior synonym of Lewisuchus admixtus. A preliminary phylogenetic analysis with updated scorings for Lewisuchus admixtusfound this species at the base of Silesauridae. Anat Rec, 00:000?000, 2019.© 2019 American Association for Anatomy