| the earliest record of birch mice from the early miocene nei mongol, china. | the earliest species of birch mouse, sicista primus sp. nov., was recovered from the 17-ma-old (early miocene) gashunyinadege locality, central nei mongol, china. it is ~9 ma older than the previous first appearance datum of sicista in eurasia. this study indicates that north american macrognathomys is a synonym of eurasian sicista, having 12 shared dental characters. as a result, the biogeography of dipodids indicates that asian sicista dispersed to north america as opposed to the hypothesis th ... | 2010 | 21113569 |