A New Titanosaurian (Sauropoda, Dinosauria) Osteoderm from the Cretaceous of Brazil and its Significance

Abstract

Titanosauria is a clade of sauropod dinosaurs that includes some of the largest terrestrial animals ever recorded. An outstanding feature of some species of this group is the presence of osteoderms, which are bony deposits on the skin that form scales, plates or other structures. Only six osteoderms have been identified from Brazil. Herein, we describe the first titanosaurian osteoderm from the Potiguar Basin (Early–Late Cretaceous) and discuss Brazilian titanosaur osteoderm diversity, their taxonomy and the functional implications. The specimen (UFRJ-DG 549-R) is bilaterally symmetrical and is assigned to the ellipsoid morphotype. The most interesting feature is the large cavities separated by thin trabeculae. This pattern, according to recent interpretations, suggests that titanosaur osteoderms functioned as a source of calcium. However, the function(s) of titanosaur osteoderms remain(s) open to debate. Compared with the other reported osteoderms from Brazil, the Potiguar osteoderm shows more similarities with an osteoderm of Ibira (Bauru Group, Turonian–Santonian) than with material collected from the Sao Luis Basin (Albian–Cenomanian) despite their greater geographical and temporal proximity. The Potiguar and Ibira osteoderms are of the ellipsoid morphotype, with no cingulum and several pits on the external surface. More findings are necessary to clarify whether the Potiguar material represents a different armored titanosaurian species in northeastern Brazil.