Jurassic swimming mammal (beaver-like docodont)

[Ken Kinman]

Dear All,
      The "beaver-like" primitive mammal from the Middle Jurassic of China (described in today's issue of Science) is causing quite a stir.  That it is aquatic is remarkable in itself, along with the amount of material (many docodonts are only known from jaws or even single teeth).  That it possessed fur is just icing on the cake.  It is apparently the largest known Jurassic mammal, but certainly NOT the largest Mesozoic mammal----the Early Cretaceous _Repenomamus giganteus_ is twice as long, and probably an even more aggressive carnivore (it appears to have a baby dinosaur in its stomach).  Clearly, not ALL Mesozoic mammals were small insectivores, even though those are the ones that were best adapted to surviving the end-Cretacous extinction.
   --Cheers,
         Ken Kinman

http://abcnews.go.com/Technology/wireStory?id=1654352

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