Earth and Atmospheric Sciences, Department of


Date of this Version



The American Museum of Natural History no. 2506


The Miocene late Arikareean land mammal "age" is largely defined by the faunal assemblage from the Agate Spring Quarries and other nearby localities in the Harrison Formation of Sioux County, Nebraska. Amphicyonid carnivores of the genera Cynelos Jourdan and Ysengrinia Ginsburg were previously known only from European Oligocene and Miocene deposits. These genera are now known from the Harrison Formation of Sioux and Box Butte counties, western Nebraska, and therefore the late Arikareean fauna now includes three amphicyonids: Cynelos sp., (?) Ysengrinia sp., Daphoenodon superbus Peterson. The stage of evolution of these carnivores suggests a correlation of the Agate Spring Quarries fauna with early to medial Aquitanian faunas of western Europe.