The first record of Onchosaurus (†Sclerorhynchidae) from the Late Cretaceous of northern Mexico

Resumen

The fossil record of
sclerorhynchid elasmobranchs in Mexico has been relatively scarce.
In this paper we report a partial rostral tooth assigned to the
cosmopolitan genus Onchosaurus (†Sclerorhynchidae), originally
preserved in a shell-bed matrix, collected at the Potrero del Llano
locality, municipality of Aldama, Chihuahua, Mexico. The specimen
most likely came from the Upper Cretaceous San Carlos Formation. The
tooth has morpho-anatomical features that allow its attribution to
the species Onchosaurus cf. O. pharao, which has been previously
described from localities in Egypt, Niger, DR of Congo, Angola,
Syria, Japan, U.S.A., Brazil, Colombia and Peru. The rostral tooth
represents the first record of Onchosaurus in Mexico and the fourth
in North America, thus expanding its paleobiogeographic
distribution.