Earliest known microtoid cricetid found from the Junggar Basin of China
Microtoid cricetids are widely considered to be the ancestral form of arvicoline rodents, a successful rodent group including voles, lemmings and muskrats. The earliest previously known microtoid cricetid is Microtocricetus molassicus Fahlbusch and Mayr 1975 from the Late Miocene (MN9, about 10-11 million years ago) of Europe. Paleontologists from Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences, described a new microtoid cricetid, Primoprismus fejfari, from the Early Miocene deposits (roughly estimated at 18–17 million years ago) of the Junggar Basin in Xinjiang, northwest China. This new record is more than 6 million years earlier than the record of M. molassicus, thus indicating a much deeper origin of microtoid rodents than previously assumed. The IVPP team reported online in the journal of Acta Palaeontologica Polonica.