Hastichthys totonacus sp. nov., a North American Turonian dercetid fish (Teleostei, Aulopiformes) from the Huehuetla quarry, Puebla, Mexico

Abstract

A new fossil needlefish species is named in this work as Hastichthys totonacus, based on specimens from the marine Turonian deposits of the Agua Nueva Formation, exposed in the Huehuetla quarry, into the Sierra Norte region of Puebla, Mexico. The osteology of this new species shows a diagnostic character of the order Aulopiformes, the occurrence of epipleurals bones associated with abdominal centra, at least from the centrum 2. This new species also shows the most distinctive features of the family Dercetidae and genus Hastichthys, including the longirostrine head; the elongated body; two pairs of triangular and expanded transverse processes in the abdominal centra; the low and elongated neural arches on abdominal centra bearing short neural spines; a row of triradiate scutes on each body flak; and the anterior part of maxilla and dentary bones are ornamented with longitudinal and parallel ridges. Hastichthys totonacus is the second species in the genus and differs from the type species, H. gracilis, in having a relatively shorter body with 59 total centra, the head length is about 38% of the standard length, the dorsal fin has seven rays, and the anal fin has eight rays. The inclusion of this new species in different phylogenetic analyses reveals that the interrelationships of the Dercetidae family are poorly resolved and that H. totonacus sp. nov. and H. gracilis form a monophyletic group. Additionally, the species Rhynchodercetis regio, from the Turonian sediments of the Agua Nueva Formation, exploited in the Vallecillo quarry, Nuevo León, northern Mexico, is also placed into the genus Hastichthys because it has the most prominent character of this genus, the tips of rostrum and mandible are ornamented with longitudinal and parallel striae and ridges. The occurrence of these two Mexican Turonian species extends the temporal and geographical distribution of the genus Hastichthys, from the Cenomanian deposits of the western Tethys Sea realm preserved in the Middle East toward the Turonian deposits of eastern Mexico, at the southern end of North America.