Propalaeocastor is a poorly-known extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of beaver

Beaver

The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...

 (family Castoridae

Castoridae

The family Castoridae contains the two living species of beaver and their fossil relatives. This was once a highly diverse group of rodents, but is now restricted to a single genus, Castor.- Characteristics :...

) from the early Oligocene

Oligocene

The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...

 of Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 and Asia

Asia

Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

. Recently described material of a new species of Propalaeocastor, P. irtyshensis, indicates that the genus is probably the earliest known member of the subfamily Castorinae (Wu et al., 2004), which includes all castorids more closely related to living beaver

Beaver

The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...

s (genus Castor) than to the extinct Giant Beaver

Giant Beaver

Castoroides ohioensis was a species of giant beaver, huge members of the family Castoridae , endemic to North America during the Pleistocene epoch .-Morphology:...

 (genus Castoroides). Previously, Propalaeocastor had been allied with more basal beavers such as Agnotocastor

Agnotocastor

Agnotocastor is an extinct member of the mammalian family Castoridae. Unlike its modern relative, this species took the place of muskrats in the rivers of North America during the Oligocene epoch....

and Anchitheriomys

Anchitheriomys

Anchitheriomys is an extinct member of the beaver family, Castoridae. Until recently, it was placed in a closely related family of rodents, Eutypomyidae , but have since described a partial skull that shows similarities to another early beaver, Agnotocastor....

(Korth, 2002). According to Wu and coauthors, Propalaeocastor, specifically P. butselensis, is the likely ancestor of the better-known Eurasia

Eurasia

Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...

n castorine Steneofiber

Steneofiber

Steneofiber is an extinct genus of beaver from Eurasia.This small, 30 cm long creature probably lived in large fresh water lakes, like present day beavers. A semiaquatic lifestyle is indicated by the presence of a combing-claw, which living beavers use to waterproof their fur. Most likely, it...

.