LEYESAURUS MARAYENSIS (DINOSAURIA, SAUROPODOMORPHA) FROM NORTHWESTERN ARGENTINA: AN UPDATE

Abstract

Leyesaurus marayensis, an early diverging sauropodomorph dinosaur, was originally described over a decade ago. It is the third
massospondylid discovered in Argentina and one of two, along with Adeopapposaurus, for which the age is not constrained yet. Here, we report a change of name for the type-bearing geological formation and the most recent studies on it. The sorting and preparation of matrix blocks from near the type locality in Balde de Leyes, Argentina, have led to a comprehensive list of sauropodomorph elements found in the area. This process resulted in the rediscovery of unprepared material belonging to the Leyesaurus holotype, prompting a revision of the original diagnosis. Notably, a previously identified partial long bone, originally thought to be metatarsal III, has been reidentified as a fibula. Additionally, three elements were rediscovered: the proximal end of a metatarsal II, a nearly complete metatarsal III, and the distal end of a pubis. Moreover, an osteohistological analysis, conducted for the first time on this material, identifies the holotypic specimen as a juvenile.