NEW SPECIES OF POSTCOPEMYS (CRICETIDAE: RODENTIA) FROM THE EARLY PLIOCENE OF LAGO DE CHAPALA, JALISCO, MEXICO

摘要

We describe a new species of cricetid rodent based on isolated molars recovered from the early Pliocene (early Blancan) Chapala Formation, Jalisco, Mexico. Compared with other named species of the genus, the new species is characterized by its large size, M1 with the median mure connected to the protocone; m1 with (1) a wide and strongly bilobed procingulum, (2) an ectolophid and ectostylid, and (3) a welldeveloped mesolophid on m1, but a short mesolophid in m2 not extending to the lingual cingulum. A preliminary phylogenetic analysis places the new species with other Postcopemys species from southwestern North America and with Jacobsomys dailyi. The new species comprises the second fossil record of the genus Postcopemys in Mexico and the southernmost record of the genus in North America. We refer the recently named J. dailyi to the genus Postcopemys.