Name: Palaeocastor ‭(‬Ancient beaver‭ ‬-‭ ‬inspired by the genus name Castor,‭ ‬which represent a modern beaver‭)‬.
Phonetic: Pay-lay-oh-kass-tore.
Named By: Joseph Leidy‭ ‬-‭ ‬1869.
Synonyms: Capacikala sciuroides,‭ ‬Steneofiber nebrascensis,‭ ‬Steneofiber peninsulatus,‭ ‬Steneofiber sciuroides
Classification: Chordata,‭ ‬Mammalia,‭ ‬Rodentia,‭ ‬Castoridae,‭ ‬Palaeocastorinae.
Species: P.‭ ‬nebrascensis,‭ ‬P.‭ ‬peninsulatus,‭ ‬P.‭ ‬magnus.
Diet: Herbivore.
Size: About‭ ‬25‭ ‬-‭ ‬30‭ ‬centimetres long.
Known locations: USA,‭ ‬Nebraska,‭ ‬Oregon,‭ ‬South Dakota‭ ‬and Wyoming.
Time period: Rupelian of the Oligocene through to the Aquitanian of the Miocene.
Fossil representation: Multiple individuals.

       Palaeocastor is most famous for the elaborate spiral burrows‭ (‬popularly known as devil’s corkscrews‭) ‬that it actually dug out using its teeth instead of its claws.‭ ‬These burrows were discovered long before the first specimen of Palaeocastor was identified,‭ ‬and had previously been interpreted as being the fossilised remains of aquatic sponges or a previously unknown type of vegetation.‭ ‬It was not until the remains of a Palaeocastor was actually found inside of one of these structures however until the real function became apparent.‭ ‬Palaeocastor are believed to have dug these burrows out using their teeth because the scratch patterns inside of these burrows match the form of their teeth.‭ ‬Because these burrows spiral down into the ground for as much as three meters below the surface,‭ ‬they would have been very good protection from the mammalian predators of the time,‭ ‬such as nimravids,‭ ‬creodonts and amphicyonids.
       Palaeocastor does not seem to have been as aquatic as the modern beaver genus Castor and this idea comes from the general construction of the burrow which is straight down into the ground.‭ ‬Modern beavers build a lodge out of wood,‭ ‬rocks and mud,‭ ‬the entrance to which is planned to be underwater.‭ ‬Aside from this, ‬Palaeocastor was still very much like a beaver in overall form.‭ ‬Study of Palaeocastor has also resulted in the idea that it was one of the few rodents to employ a k-strategy to reproduction.‭ ‬K-strategy is where the parent animals actually invest a greater amount of time and effort into just razing a small number of young which will accompany their parents until they are almost fully grown.‭ ‬This is in contrast to most other rodents that repeatedly produce large litters of young because their species mortality from predators is so high‭ (‬r-strategy‭)‬.

Further reading
-‭ ‬Notice of remains of extinct Mammalia,‭ ‬discovered by Dr.‭ ‬F.‭ ‬V.‭ ‬Hayden in Nebraska Territory,‭ ‬Joseph‭ ‬Leidy‭ ‬-‭ ‬1856.
-‭ ‬A large Palaeocastor from the Lower Miocene,‭ ‬A.‭ ‬S.‭ ‬Romer‭ & ‬J.‭ ‬T.‭ ‬McCormack‭ ‬-‭ ‬1928.


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