MORPHOLOGY AND HISTOLOGY OF OSTEODERMS FROM A PEIROSAURID FROM THE NEUQUEN BASIN. Osteoderms of a new crocodyliform specimen recovered from the Puesto Hernández locality are described here, found in sediments of the Plottier Formation (late Coniacian), near Rincón de los Sauces city, Neuquén Province. The studied osteoderms, that are part of the associated material, include: dorso-sacral region, appendicular osteoderms associated to the right femur, proximoventral region of articulated caudal osteoderms, and isolated osteoderms. The histology of the osteoderms allowed determining they have a compact cortex that surrounds a more cancellous internal region. It was possible to recognize growth marks (annuli) in the entire compact tissue, indicating a minimum age of 18 years for the studied specimen. The osteoderms have characters that allow preliminarily assigning the specimen MAU-Pv-PH-437 to Mesoeucrocodylia closely related to Peirosauridae.