Articles | Volume 21, issue 1
Research article
28 Mar 2018
Research article |  | 28 Mar 2018

A new pachyrhizodontid fish (Actinopterygii, Teleostei) from the Muhi Quarry (Albian-Cenomanian), Hidalgo, Mexico

Gloria Arratia, Katia A. González-Rodríguez, and Citlalli Hernández-Guerrero

Abstract. A new genus and species – Motlayoichthys sergioi (ZooBank registration:, – from the Cretaceous (Albian-Cenomanian) of the Muhi Quarry, Hidalgo, central Mexico is assigned to the family Pachyrhizodontidae based on the presence of the inner premaxillary tooth and a few other cranial characters. Its unique suite of characters, that includes several autapomorphies supports its assignment as a new genus and species, such as the presence of a triangular head with three sides of similar lengths and with its deepest part at the level of the supraoccipital region; the lower jaw projecting anterior to the premaxilla; the ornamentation of cranial bones – especially those of the cheek region – consisting of fine longitudinal crests densely covering the bony surfaces; one or a few deep grooves on the mandibular teeth, which in addition bear acrodin tips ornamented with fine parallel striae; and the position of the dorsal fin, near the posterior margin of the cranium. Motlayoichthys n. gen., together with Michin, Pachyrhizodus, Rhacolepis, and Notelops, is part of the early radiation of pachyrhizodontoids during Albian times.

Short summary
A new species of a group of extinct fishes with a worldwide distribution during the Cretaceous, about one hundred million years ago, is described. Motlayoichthys sergioi is an outstanding fossil fish from Mexico with unique characters within the Pachyrhizodontidae. This fish is part of a diverse fauna found in a limestone quarry in Central Mexico. The goal of this paper was to contribute to the knowledge of the family and to continue the study of the Muhi Quarry fish, endemic to Mexico.