Mammals take to the water
A beaver-tailed, otter-limbed swimmer shows Jurassic mammals were far from uniformly small and timid.
- When
- Known to
- ± 3 million years
- Era
- Jurassic, Mesozoic
Castorocauda lutrasimilis, about 164 million years old, had a flat scaly tail, paddling limbs, probably webbed feet and seal-like fish-catching teeth — and preserved fur, among the earliest direct evidence of mammalian hair. It weighed perhaps 800 grams, large for its time. Mammals were already exploiting specialised niches long before the dinosaurs left.