Jurassic “beaver” from China found
and World Science staff
It had a broad scaly tail, fur, swimmer’s limbs and seal-like teeth for eating fish, and it lived 164 million years ago, researchers say.
The discovery of an extraordinarily well-preserved beaver-like mammal fossil from Middle Jurassic era in China suggests mammals may have been a more diverse group during the dinosaur era than previously thought, a study suggests.
Researchers say the finding shows mammals expanding into a variety of environmental niches even as dinosaurs still ruled the earth. The new species, Castorocauda lutrasimilis, is an unusual fossil in a number of ways, say Qiang Ji of Nanjing University in Nanjing, China and colleagues.
The finding appears in the Feb. 24 issue of the research journal Science.
The discovery “pushes back the mammalian conquest of the waters by more than 100 million years.” Wrote Thomas Martin of The Senckenberg Research Institute and in Frankfurt am Main, Germany, wrote in a commentary in the journal. The Jurassic lasted from 190 million to 135 million years ago
Researchers said the fossil provides a wealth of information compared compared to the teeth and few scraps of skull known from most mammal fossils of its time period. Castorocauda has uniquely well preserved fur and scale imprints, along with the suggestion of soft tissue webbing in the hind limbs and partial skeleton, they said.
Castorocauda is also the largest known Jurassic early mammal, they added, about the size of a small female platypus.
The combination of some primitive skull features and the specialized features of fur, swimming and burrowing adaptations and fish-eating all indicate that early mammals had begun to specialize and move into new environments long before the dinosaurs’ end 65 million years ago, researchers say.
Traditional thinking has it that mammals had to wait until the dinosaurs died out to find significant new ecological niches to move into. But recent findings have been chipping away at that belief, including finding last year of a fierce mammal that ate dinosaur babies.
* * *
Send us a comment
on this story, or send
it to a friend