Jurassic beaver swims into view - Large early mammal was first to get furry. From nature.com
Ever see the cliché ending to virtually every program on the extinction of the dinosaurs where the Tyrannosaurus Rex skull lies in the sand with the mouse-like mammal crawling out its eye socket?
Until now, the fossil record has only yielded small, shrew-like mammals living during the Mesozoic Era (Triassic, Jurassic & Cretaceous periods). The assumption has been that dinosaurs so completely dominated that era mammals were unable to thrive until the following Cenozoic era.
This new find out of China is an amazingly advanced beaver from Jurassic period China.
While this certainly means a re-think of when mammals began their advance towards world-dominance this doesn’t seem as surprising to me. Prior to the Mesozoic, during the Paleozoic, the earth was dominated by creatures known as the Mammal-like reptiles (Therapsids). These were displaced during the Triassic by dinosaurs and apparently gone by the Jurassic, but they are the direct ancestors of mammals. It doesn’t seem that impossible that mammals had more of a head start than previously thought.
The process of fossilization requires being at the right place at the right time, and some places (rivers, seas, oceans) are more conducive than others. Further, those places now have to be exposed. There are certainly far more creatures that did exist than we could ever possibly expect to find.
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