Name: Castorocauda ‭(‬beaver tail‭).
Phonetic: Cas-to-ro-caw-dah.
Named By: Q.‭ ‬Ji,‭ ‬Z.-X.‭ ‬Luo,‭ ‬C.-X.‭ ‬Yuan‭ & ‬A.‭ ‬R.‭ ‬Tabrum‭ ‬-‭ ‬2006.
Classification: Chordata,‭ ‬Synapsida,‭ ‬Therapsida,‭ ‬Cynodontia,‭ ‬Mammaliaformes,‭ ‬Docodonta,‭ ‬Docodontidae.
Species: C.‭ ‬lutrasimilis‭ (‬type‭)‬.
Diet: Carnivore.
Size: At least‭ ‬42.5‭ ‬centiemetres long for the holotype.
Known locations: China,‭ ‬Lianoning Province‭ ‬-‭ ‬Tiaojishan Formation.
Time period: Callovian of the Jurassic.
Fossil representation: Almost complete individual.

       For lack of a better description,‭ ‬Castorocauda was basically like an otter or beaver that lived during the Jurassic.‭ ‬However,‭ ‬while Castorocauda superficially looks like them,‭ ‬the genus is in no way a direct relation to them,‭ ‬Instead,‭ ‬Castorocauda is what is known as a docodont mammaliform,‭ ‬and a member of a group that has no surviving descendents today.‭ ‬Nevertheless,‭ ‬the genus and type species name of Castorocauda lutrasimilis does translate as‭ ‘‬beaver tail similar to otter‭’‬.
       The adaptations made by Castorocauda to a semi-aquatic lifestyle are interpreted as being a case of convergent evolution,‭ ‬the process where two unrelated animals evolve the same adaptations to deal with the same survival situation.‭ ‬Castorocauda would have spent time hunting within the water,‭ ‬perhaps looking for fish and/or crustaceans while returning to land to rest and raise young.‭ ‬While on land Castorocauda would have been more vulnerable to predators especially smaller theropod dinosaurs.‭ ‬Modern otters usually shelter in burrows however,‭ ‬and this raises the question,‭ ‬if Castorocauda developed similar a body form to otters,‭ ‬then did Castorocauda also develop similar behaviour too‭?

Further reading
-‭ ‬A swimming mammaliaform from the middle Jurassic and ecomorphological diversification of early mammals.‭ ‬-‭ ‬Science‭ ‬311:1123-1127.‭ ‬-‭ ‬Q.‭ ‬Ji,‭ ‬Z.-X.‭ ‬Luo,‭ ‬C.-X.‭ ‬Yuan‭ & ‬A.‭ ‬R.‭ ‬Tabrum‭ ‬-‭ ‬2006.


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