Ankylosaurian remains from a new Campanian–Maastrichtian locality in Northern Patagonia, Argentina

Abstract

In South America, the fossil record of thyreophorans is scarce compared to that of Laurasian landmasses. The first findings of armored dinosaurs date back to the first half of the 20th century consisting of an isolated scute and incomplete caudal vertebrae from Late Cretaceous beds in northern Patagonia. For decades, ankylosaurian remains from South America were represented by isolated and poorly informative specimens, but this changed recently with the discovery of a nearly complete skeleton of Stegouros elengassen, from Maastrichtian beds in southern Chile. The aim of the present study is to report new fossils of armored dinosaurs coming from Allen Formation beds (Late Cretaceous, Campanian-Maastrichtian) in the Arriagada Farm fossiliferous locality, Salitral Ojo de Agua, Río Negro province. The new specimens include teeth, scutes, and a partial sacrum belonging to at least three individuals. These specimens come from a different locality than the coeval Patagopelta cristata, which is the only named armored dinosaur from argentine Patagonia. Some of the specimens were found intermingled with bones and eggs belonging to the alvarezsaurid theropod Bonapartenykus ultimus, being the first finding of this dinosaur assemblage in South America.