A reassessment ofMegamacaca lantianensis, a large monkey from the Pleistocene of north-central China

Megamacaca lantianensis, a cercopithecid of Early Pleistocene age from the Gongwangling locality of Lantian, Shaanxi Province, China, was first described in 1978 as a large cercopithecine with affinities to the living and fossil macaques of China. Recent examination of the type series has indicatedM. lantianensis is a large colobine rather than a cercopithecine.Megamacaca lantianensis was found to share several derived dental characters with extant Asian colobines, but not withMacaca. Characters unitingM. lantianensis to the Colobinae but not to the Cercopithecinae included a relatively wide P₃ and lower molars with relatively short trigonids, high relief, and deeply incised lingual notches. Further, it was found thatM. lantianensis shared several derived characters withRhinopithecus (and its sister taxonPygathrix) that it did not share with other colobines. These features included: (1) a high and vertically oriented mandibular ramus; (2) a three-cusped P³; (3) irregularly wrinkled enamel on the unworn occlusal surfaces of the molars; (4) the presence of accessory cusplets, conules, and styles on the molars; and (5) molars with somewhat puffy buccal and lingual surfaces. Similarities in the morphology of the ramus, body, and symphysis of the mandible ramus between the fossil form andRhinopithecus (but notPygathrix) have led to the conclusion thatMagamacaca should be synonymized withRhinopithecus and that the Gongwangling cercopithecid be henceforth referred to asRhinopithecus lantianensis.