The path of giants: a new occurrence of Rebbachisauridae (Dinosauria, Diplodocoidea) in the Açu formation, NE Brazil, and its paleobiogeographic implications

The Rebbachisauridae (Diplodocoidea) comprises small to medium-sized sauropods that diversified at the end of the Early Cretaceous-beginning of the Late Cretaceous in Africa, South America and Europe. The goal of this paper is to review the distribution of fossils assigned to Rebbachisauridae at Early-Late Cretaceous and describe the first occurrence of this group in the Açu Formation, Potiguar Basin, Brazil. The material consists of five isolated caudal vertebrae. The specimens have the combination of some characteristics shared with rebbachisaurid taxa, such as Limaysaurus, Amazonsaurus and Demandasaurus: (i) the anterior and posterior articular facets of the centrum are sub-hexagonal to sub-quadrangular; (ii) they bear a wide base; (iii) the centrum presents an amphicoelic condition; (iv) the centrum lacks pneumatization in both lateral and ventral surfaces; (v) an anterior position of the neural arch is implied by the anteriorly located centroneural suture of the centrum (Salgado et al., 1997; Wilson and Sereno, 1998; Canudo et al., 2018). The rebbachisaurids have been largely used for biogeographical interpretations due to its presence in both Gondwanan and Laurasian continents; the material presented here is a further evidence of this relationship once the specimens show similarities with both European and Argentinean forms. Furthermore, this occurrence enlarges the presence of the group in Brazil and South America, and is important for a better understanding of the faunistic context of the Northeast of South America and its relationship with other Early-Late Cretaceous faunas.