A Pliocene goodeid fish of the Paleolake Amajac, Sanctórum, Hidalgo, Mexico

Abstract

The splitfin fossil species Paleocharacodon guzmanae gen. and sp. nov. is erected based on the osteological study of 14 fossil male and female specimens recovered in the Pliocene deposits of the Paleolake Amajac, in Sanctórum, Hidalgo, Mexico. This new cyprinodontiform fish exhibits the diagnostic features of the family Goodeidae and subfamily Goodeinae; like all the goodeids, its premaxilla has a straight distal end, and its premaxillary ascending process is small; and, like the goodeines, this new species was viviparous, its first anal fin ray is rudimentary, and the males show an andropodium. Although P. guzmanae displays numerous primitive features, it is not possible to place it in any of the goodeine tribes, which currently are vaguely defined by osteological features. This new species seems to be closely related to Characodon; both share a peculiar osteological character; the articular facet for the quadrate is a donut-like structure, in which the retroarticular forms the central region, and a couple of semicircular anguloarticular processes form the surrounding part. This species differs from other goodeids mainly in two features; it has a posttemporal bone with small anteroventral processes, and the openings of its supraorbital canal show the formula12a, 2b-3a, 3b-4a, 4b-5a, and 5b-7. The discovery of this extinct goodeid species in the great Pánuco-Salado Basin on the eastern slope of Mexican territory represents an unexpected historical element. Carmen Caballero-Viñas. Departamento de Paleontología, Instituto de Geología, Universidad Nacional Autónoma de México. Circuito de la Investigación S/N, Ciudad Universitaria, Coyoacán, Ciudad de México, 04510, Mexico. c-caballero@live.com.mx Jesús Alvarado-Ortega. Departamento de Paleontología, Instituto de Geología, Universidad Nacional Autónoma de México. Circuito de la Investigación S/N, Ciudad Universitaria, Coyoacán, Ciudad de México, 04510, México. alvarado@geología.unam.mx Kleyton Magno Cantalice Severiano. Departamento de Paleontología, Instituto de Geología, Universidad CABALLERO-VIÑAS ET AL.: PLIOCENE GOODEID FROM MEXICO 2 Nacional Autónoma de México. Circuito de la Investigación S/N, Ciudad Universitaria, Coyoacán, Ciudad de México, 04510, México. kleytonmc@geologia.unam.mx