A NEW TITANOSAURIAN (SAUROPODA, DINOSAURIA) OSTEODERM FROM THE CRETACEOUS OF BRAZIL AND ITS SIGNIFICANCE --- Preprint doi:10.5710/AMGH.14.11.2017.3094

Paulo V. Gomes Da Costa Pereira, Thiago Da Silva Marinho, Carlos R. Dos Anjos Candeiro, Lilian Paglarelli Bergqvist

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, bony deposits on the skin that form scales, plates or other structures. Only six osteoderms have been identified from Brazil. Here, we describe the first titanosaurian osteoderm from the Potiguar Basin (Early–Late Cretaceous) and discuss Brazilian titanosaur osteoderm diversity, their taxonomy, and functional implications. The specimen (UFRJ DG 549-R) is bilaterally symmetrical and is assigned to the ellipsoid morphotype. Its internal face is flattened, and its external face forms a prominent bulb. Internally, the osteoderm consists of trabecular bone and matrix-filled space; compact bone is present only in the outer region. 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 remains open to debate. Compared to the other reported osteoderms from Brazil, the Potiguar osteoderm shows more similarities with an osteoderm of Ibirá (Bauru Group, Turonian-Santonian), than to material collected from the São Luís Basin (Albian-Cenomanian), despite their greater geographical and temporal proximity. The Potiguar and Ibirá osteoderms are ellipsoid morphotype, with no cingulum and several pits on the external surface. More findings are necessary to clarify whether or not the Potiguar material represents a different armored titanosaurian species in northeastern of Brazil.

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