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

A new genus and species – <i>Motlayoichthys sergioi</i> (ZooBank registration: urn:lsid:zoobank.org:pub:2C503741-2362-4234-8CE0-BB7D8BE5A236, urn:lsid:zoobank.org:act:EF5040FD-F306-4C0F-B9DA-2CC696CA349D) – 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. <i>Motlayoichthys</i> n. gen., together with <i>Michin</i>, <i>Pachyrhizodus</i>, <i>Rhacolepis,</i> and <i>Notelops</i>, is part of the early radiation of pachyrhizodontoids during Albian times.