Propalaeocastor
Propalaeocastor is a poorly known extinct genus of beavers (family Castoridae) from the early Oligocene of Europe and Asia. Recently described material of a new species of "Propalaeocastor", "P. irtyshensis", indicates the genus is probably the earliest known member of the subfamily Castorinae, which includes all castorids more closely related to living beavers (genus "Castor") than to the extinct giant beaver (genus "Castoroides"). Previously, "Propalaeocastor" had been allied with more basal beavers such as "Agnotocastor" and "Anchitheriomys". According to Wu and coauthors, "Propalaeocastor", specifically "P. butselensis", is the likely ancestor of the better-known Eurasian castorine "Steneofiber".