First record of the genus Vinalesphinctes (Ammonitina) in the Oxfordian of Mexico: Biostratigraphic and paleobiogeographic significance in the Upper Jurassic of the Americas

Abstract

The genus Vinalesphinctes (Ammonitina) is reported for the first time from Mexico. The studied specimens were collected from two Oxfordian sections of the east-central Mexico, Huasteca region, Hidalgo and San Luis Potosi states. Two morphospecies have been identified, Vinalesphinctes tamanensis and Vinalesphinctes tenangensis. Mexican, Cuban and Chilean Vinalesphinctes are compared, and a late Oxfordian, Bifurcatus Chron age is interpreted for the Mexican forms. Within the context of limitations derived from the scarcity of the material available, the taxonomical differentiation proposed for Mexican Vinalesphinctes is in accordance with the ecological interpretation (i.e., envisaged habitat), and reinforces hypotheses about endemism affecting ammonites during the Chron Bifurcatus in the American regions considered However additional research is necessary before giving a conclusive interpretation about the causal factors for the ammonite scarcity during the Late Oxfordian of the Mexico-Caribbean region.