A new sclerorhynchiform (Elasmobranchii) from the Middle Cretaceous of Brazil

Abstract

A new species and a new genus of sclerorhynchids (Elasmobranchii), Atlanticopristis equatorialis, is recorded from the early Cenomanian deposits of the Alcântara Formation, Itapecuru Group of northeastern Brazil. Fourteen rostral teeth were collected at the Falesia do Sismito exposure, Cajual Island, northern Maranhao State. The holotype, VT- 1174, is slightly recurved and compressed, 15 mm long, including the penducle, which is 6.3 mm long antero-posteriorly, and has a thickness of 3 mm. Both sides are barbed in all specimens. VT-1174 exhibits 4 barbs along the anterior margin and 5 on the posterior one. Barb number varies among the specimens; some specimens possess more barbs than the holotype, and one specimen has more barbs on the anterior margin than on the posterior one. On dorsal and ventral faces, nearly straight enameloid ridges emanate from the crown base. They diverge from each other apically, forming the frame of a fan. More lateral ribs intersect the base of a barb, but central ribs are nearly parallel and terminate close to the base of the crown. On some specimens, more lateral enameloid ridges fail to reach more apical barbs. Some specimens exhibit a medial longitudinal groove on both surfaces. The peduncle is antero-posteriorly expanded and irregularly fluted, laterally compressed, tending to be ellipsoidal or sub-rectangular in basal outline. This new taxon occurs in the same estuarine deposits where Onchopristis numidus was previously reported, thus increasing the known diversity of fishes, Elasmobranchii in particular, from the middle Cretaceous of northeastern Brazil.