A small Hemiauchenia from the late Pleistocene of Hidalgo, central Mexico

Pleistocene camels from Mexico include representatives of llamas and camels, whose record spans from the early Blancan to the late Pleistocene based on several localities in the northern, northwestern and central parts of the country. Particularly, members of the genus Hemiauchenia are well represented. New specimens collected in the state of Hidalgo, central Mexico, belonging to a small llama, are assigned to Hemiauchenia gracilis owing to a combination of cranial and postcranial characters, including a short upper premolar-molar series, the presence of a two-rooted P3, molars covered by a thin layer of cementum, U-shaped molar crescents, well-developed styles and ribs, a small degree of crenulation, a relatively short lower tooth row, the lack of p1 and p3, weakly-developed anteroexternal stylids, a shallow and slender mandible, and long and slender metatarsals and phalanges. The material described here extends the Pleistocene geographic distribution of H. gracilis from northern to central Mexico, and its biochronological range from the early Blancan to the late Pleistocene (Rancholabrean), thus making it the southernmost record and the geochronologically youngest occurrence of this species in North America. The mesowear pattern of the material from Hidalgo suggests that these animals were mainly browsers, and their estimated body mass resembles that of Blancan specimens from Guanajuato, implying that this species maintained approximately the same body mass throughout its biochronological range in central Mexico.