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. History 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 gomphodont and bones from several other species of archosaurs were also preserved in the same nodule. An isolated lower jaw and foot bones were also initially referred to Lewisuchus, but these were later identified as belong to proterochampsids. This is also likely true of an astragalus found alongside the skeleton. Alfred Romer named Lewisuchus as a new genus in 1972, based on the partial skeleton which at that point was stored at the Museo de La Plata with catalogue number 64-XI-14-14. The generic name honored Arnold D. Lewis, the chief preparator who discovered the skeleton while working on the recovered nodule. Like many other early archosaurs and crocodilian relatives, it also references Soûkhos, the Greek name for the Egyptian crocodile god Sobek. The species name "admixtus" refers to the mixture of different species preserved along with the holotype. The holotype is now housed at the Paleontology Museum at the National University of La Rioja (PULR) with catalogue number PULR 01. Pseudolagosuchus Another Chañares archosaur was described by Andrea Arcucci in 1987. This archosaur encompassed four specimens stored at the Miguel Lillo Institute (PVL) of the University of Tucuman, the PULR, and the Museo Argentino de Ciencias Naturales (MACN). Arcucci named a new archosaur genus based on these specimens: Pseudolagosuchus major. It was originally considered a close relative of its namesake, the small dinosauriform Lagosuchus. The holotype of Pseudolagosuchus, PVL 4629, included most of a left hindlimb and pelvis as well as a fragmentary ankle, vertebrae, and ribs. Other specimens included PVL 3454 (fragments of the hip and hindlimb), MACN 18954 (vertebrae and portions of the hindlimb and ankle), and PULR 53 (tail vertebrae and bones from the ankle region).