Xiphophorus gordoni, A New Species of Platyfish from Coahuila, Mexico

Xiphophorus gordoni, the third new species of this genus to be made known since 1959, is described and figured from the arid, semi-isolated Cuatro Cienegas basin of central Coahuila, Mexico. It is based on meristic, morphometric, and osteological data-and observations of living material in the field and laboratory-involving more than 200 individuals. The new species is related to X. couchianus, from the vicinity of Monterrey, and to X. variatus xiphidium, from the basin of the Rio Soto la Marina-possibly more intimately to the latter. X. gordoni is known only from a single body of water, of which a photograph is presented. It is one of a number of fishes endemic to the Cuatro Cienegas basin.