Lewisuchus

Extinct genus of reptiles

Lewisuchus is a genus of archosaur that lived during the Late Triassic (early Carnian). As a silesaurid dinosauriform, it was a member of the group of reptiles most commonly considered to be the closest relatives of dinosaurs (possibly true dinosaurs themselves). Lewisuchus was about long. Fossils have been found in the Chañares Formation of Argentina. It exhibited osteoderms along its back.

The first remains of Lewisuchus were discovered in a 1964 1965 joint expedition by the Museo de La Plata and Harvard's Museum of Comparative Zoology. These remains were preserved in a carbonate nodule recovered from the Chañares Formation of Argentina. It contained a partial skeleton of Lewisuchus, including parts of the skull, braincase, many vertebrae, scapulocoracoids, humeri, and tibiae. A 1996 study on dinosaur origins by Fernando Novas also placed a well preserved femur and tibia (erroneously labelled UPLR 53) within the genus, and this may also be the case with PVL 3455, an indeterminate partial skeleton with some similarities to Arcucci's original material. Many other studies supported these arguments, sometimes even scoring the two as a single taxon in their phylogenetic analyses. Several hindlimb, hip, and vertebral fossils (PVL 3456, PULR V 112 and PULR V 113) have additionally been referred to Lewisuchus based on their similarity to Pseudolagosuchus remains. However, Bittencourt et al. 's 2014 redescription of the Lewisuchus holotype refrained from synonymizing the two due to a lack of data, with the only overlapping material being the tibia and a few cervical (neck) vertebrae. No unambiguous characteristics were shared between these scraps, and one tibia referred to Pseudolagosuchus (Novas's 'UPLR 53') seemed to have a curvature different from that of Lewisuchus's holotype.