New diatomyid and baluchimyine rodents from the Oligocene of Pakistan (Bugti Hills, Balochistan): systematic and paleobiogeographic implications

Abstract

ABSTRACT The rodents (Baluchimyinae and Fallomus) from the Bugti, Sulaiman, and Ladakh deposits (Indian subcontinent) were originally considered a distinct early Miocene group that arose via local evolution from the Eocene Chapattimyidae in the Indo-Pakistan province. The Bugti Member, the lowermost continental beds of the previously ascribed Miocene Chitarwata Formation, is now considered to be Oligocene. A new continental vertebrate locality from the basal part of the Bugti Member (Paali naia C2) has yielded an important early Oligocene small mammal fauna including a well-diversified rodent assemblage that allows revision of the age attributed to the classic Bugti rodent fauna. Additional specimens (mainly isolated teeth) allow a systematic review of Fallomus (Diatomyidae) and Hodsahibia (“Baluchimyinae”), and two new species are described for each genus (F. ginsburgi, sp. nov.; F. quraishyi, sp. nov.; H. gracilis, sp. nov.; and H. beamshaiensis, sp. nov.). The presence of several higher rodent taxa at Paali naia C2 suggest that there was not an extended period of mid-Tertiary faunal isolation on the Indian subcontinent, nor an abrupt turnover between Chitarwata and Lower Siwalik rodent faunas. “Baluchimyines,” here considered Hystricognathi incertae sedis, are part of a diverse assemblage of hystricognathous rodents in South Asia at the end of the Paleogene. A close phylogenetic relationship between “baluchimyines” and earliest Asian hystricid rodents is plausible.