New Rodent Material from the John Day Formation (Arikareean, Middle Oligocene to Early Miocene) of Oregon

• DOI: 10.2992/007.083.0102
• Publication Date: 2015-06-03T13:58:43Z
• Authors: William W. Korth; Joshua X. Samuels
• Keywords: 0106 biological sciences; 15. Life on land; 01 natural sciences

The John Day Formation of Oregon is one the richest and best studied assemblages in North America. Including seven members spanning about 20 million years, there are over 150 vertebrate species known from Formation. rodent faunas have not been as well larger mammals, with many families having received little attention last hundred years. Here, twenty rodents described, based on new discoveries previously unpublished specimens material includes four genera species; eutypomyid Allotypomys pictus, anchitheriomyine castorid Microtheriomys brevirhinus, eomyid Proapeomys condoni, heteromyid Bursagnathus aterosseus; six species: sciurine sciurid Miosciurus covensis, eomyids Apeomys whistleri Neoadjidaumo arctozophus, heteromyids Proheteromys latidens Trogomys oregonensis, sicistine dipodid Plesiosminthus fremdi. problematical species, "Florentiamys" lulli Wood, 1936a, referred questionably a combination, ?Proapeomys (Wood, 1936a). Emended diagnoses ballovianus (Cope, 1881) thorpei 1935b, offered upon substantially more complete than was for either. Biostratigraphic ranges newly described allow direct comparison other contemporaneous These also better reconstruction past ecosystems vital understanding how changed through time region.