A new species of crown-antlered deerStephanocemas(Artiodactyla, Cervidae) from the middle Miocene of Qaidam Basin, northern Tibetan Plateau, China, and a preliminary evaluation of its phylogeny

Abstract

Stephanocemas Colbert, 1939 is one of the earliest groups of deer (Cervidae) that shows indications of shedding their antlers, and as such, occupies a special position in the transition from nondeciduous to deciduous antlers in the evolution of cervids. Despite this basal position in cervid phylogeny, however, it has a highly peculiar, palmate antler morphology that is easily recognized in the fossil records of the early to middle Miocene of Eurasia. A new species, Stephanocemas palmatus sp. nov., is described based on three partial antlers ranging from juvenile to full adult individuals, recently collected from the late middle Miocene Lower Youshashan Formation in the Qaidam Basin of northern Tibetan Plateau. Another indeterminate species (Stephanocemas sp.) of much smaller size and primitive characteristics is described from more fragmentary materials in strata lower than the level of S. palmatus but still middle Miocene in age. To the extent that it was possible, we also attempted to place into modern stratigraphical context historical collections of Stephanocemas from Qinghai Province that were obtained during the Sino-Swedish Expeditions in the 1930s. These materials were described by Birger Bohlin in 1937 but their stratigraphical context has been in question ever since. A species-level phylogeny suggests that S. palmatus is the most derived among known species, with its large size, great expansion of the palm part of the antler, and horizontally radiating tines. We recognize a Paradicrocerus clade that includes P. flerovi Gabuniya, 1959, P. elegantulus (Roger, 1898), and P. brevistephanos (Baschanov & Nurumov, 1955); the latter two were traditionally regarded as belonging to Stephanocemas. As a result, the Paradicrocerus clade is largely European and western Asian, whereas the restricted Stephanocemas is now Asiatic in geographical distribution. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 156, 680–695.