This wee skull of a Microtheriomys brevirhinus from the John Day Formation is an adorable 19 mm. Yeah, he's pretty cute!
Paleontologists Dr William Korth of Rochester Institute of Vertebrate Paleontology and Dr Joshua Samuels of John Day Fossil Beds National Monument are pretty chuffed about some new fossil finds. They have described four new genera and ten new species of prehistoric rodents that lived in what is now Oregon during the Oligocene -- 30- 22 million years ago.
The newly-discovered genera include this wee fellow, the early beaver, Microtheriomys brevirhinus, a dwarf tree squirrel, Miosciurus covensis, a primitive pocket mouse, Bursagnathus aterosseusm the birch mouse Plesiosminthus fremdi, an early relative of beavers, Allotypomys pictus along with bits and pieces of Proapeomys condoni; Apeomys whistleri; Neoadjidaumo arctozophus, Proheteromys latidens & Trogomys oregonensis.
Of these ten new species, four represent completely new genera: Allotypomys, Microtheriomys, Proapeomys, and Bursagnathus.
“This study fills some substantial gaps in our knowledge of past faunas, specifically smaller mammals,” said Dr Samuels, who is a co-author of the paper published in the Annals of Carnegie Museum. “Some of the new species are really interesting in their own right, and will ultimately help improve our understanding of the evolution of beavers and pocket mice.” The new rodents were collected through decades of collaborative work throughout the John Day Formation, Oregon.