[dinosaur] Lewisuchus specimen from Chañares Forma tion from Argentina

Ben Creisler
[email protected]

A new paper:

Martín D. Ezcurra,  Sterling J. Nesbitt,  Lucas E. Fiorelli  & Julia B.
Desojo (2019)
New specimen sheds light on the anatomy and taxonomy of the early Late
Triassic dinosauriforms from the Chañares Formation, NW Argentina.
The Anatomical Record (advance online publication)
doi:  https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1002_ar.24243&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=FkSAwlH-U4UC6VlI9oRkz1vMFpd2P2VJAyut4OiPJaU&s=Ph63dUPVrI3LEeHm-d4tVk4wKB1mzqMH1Pt9Pli9R-k&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_10.1002_ar.24243&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=FkSAwlH-U4UC6VlI9oRkz1vMFpd2P2VJAyut4OiPJaU&s=q5sTXFDUs-cdmoaBTobpQkR1NbCiKKJTrFDw9UBipSs&e= 


The lower Carnian levels of the Chañares Formation (Ischigualasto‐Villa
Unión Basin, La Rioja Province) have yielded some of the most informative
dinosaur precursor species known so far. However, these species are based
on partial skeletons that in several cases hamper the comparison between
them because of the absence of overlapping bones. This has generated a
contentious debate during the last 20 years about the synonymy between two
of these species, Lewisuchus admixtus and Pseudolagosuchus major. Here, we
describe a new dinosauriform partial skeleton (CRILAR‐Pv 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 comparisons with
other dinosauriform specimens. CRILAR‐Pv 552 is referred to Lewisuchus
admixtus because it possesses a proportionally large skull, a laterally
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 dentary
associated with the holotype of Lewisuchus admixtus. Additionally, the
morphology of the new specimen is completely congruent with that of
specimens of Pseudolagosuchus major, bolstering the hypothesis that the
latter species is a subjective junior synonym of Lewisuchus admixtus. A
preliminary phylogenetic analysis with updated scorings for Lewisuchus
admixtus found this species at the base of Silesauridae.

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