A new leptarctine (Carnivora: Mustelidae) from the early Miocene of the northern Tibetan Plateau:: implications for the phylogeny and zoogeography of basal mustelids

A recently discovered basal mustelid carnivoran, Kinometaxia guangpui gen. et sp. nov, is described from the lower Miocene Tiejianggou Formation in the Danghe (Tabenbuluk) area of the northern Tibetan Plateau, north-western Gansu Province, China. The new Chinese form has a double temporal crest and roughened surface on the temporal area, a small orbit, a deep zygomatic arch, an anterolaterally expanded ectotympanic that fuses with the postglenoid process, and a lateral opening of the postglenoid foramen. These cranial morphologies suggest membership in the leptarctines, a group of markedly hypocarnivorous taxa mostly confined to the Miocene of North America. The rather hypercarnivorous dentition of the new Chinese form, however, is in sharp contrast to that of the traditionally defined leptarctines that have complex and quadrate M1s and P4s. Phylogenetic analysis suggests a sister relationship of the new Chinese mustelid and Schultzogale, and together they form a basal sister clade to the advanced leptarctines such as Craterogale, Leptarctus, and Hypsoparia. The Chinese form further expands the concept of the leptarctine clade and adds additional complexity to the early evolution of the Mustelidae. It bridges a morphological gap between European and North American taxa, and supplies an important piece to the puzzle of the zoogeography of basal mustelids. Furthermore, the new leptarctine helps to constrain the age of the Danghe strata, which has important implications for the timing of tectonic activity in the northern Tibetan Plateau. (C) 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 142, 405-421.