A new crossognathiform fish (Teleostei: †Crossognathiformes) from San José de Gracia quarry reveals a great diversity in the Cretaceous outcrops of Mexico

Abstract

We describe a new species, †Buapichthys gracilis gen. et sp. nov., based on two specimens from the Turonian deposits of the San José de Gracia quarry, Molcaxac, Puebla, central Mexico. Osteological features show this new species belongs to the order †Crossognathiformes, nesting within the suborder †Pachyrhizodontoidae. The combination of features, such as a slender body, the head with cephalic spines, three hypertrophied postcleithra, the pelvic fin posterior to the dorsal fin, the first and last dorsal pterygiophores modified into scutes, and the dorsal fin bony projections shows that †Buapichthys gracilis gen. et sp. nov. is different from other crossognathiform. This new taxon represents an increase in the group's diversity, constituting the seventh species of the order †Crossognathiformes reported in Mexico. Evaluating the crossognathiform biodiversity over time indicates that the great crossognathiform diversification occurred during the Albian until the Turonian. The Mexican fossil record significantly contributes to this diversity, with about 18 % of the species recognized for this period.