24 February 2006

Natural Geographic shows off its beaver

Somehow I can’t imagine this stomping through a park, kicking over jeeps and gobbling up scientists.

Nicholas Bakalar describes 17-inch-long Castorocauda lutrasimilis (AKA “beaver-tailed otter-like”):

A well-preserved fossil mammal discovered in northeastern China has pushed the history of aquatic mammals back a hundred million years [to 164 million years ago ...].

It is the oldest swimming mammal ever found and the oldest known animal preserved with fur [...].

Until now, the oldest mammal fossils found with fur [...] were about 125 million years old.

Most mammal specimens this old consist of no more than a few broken, fossilized bones. But this specimen is an almost complete skeleton.

Even tiny middle-ear bones are intact. The well-preserved teeth—incisors, canines, premolars, and molars—look to have been ideal for feeding on fish and aquatic invertebrates, somewhat like the teeth of modern seals.

Most significantly, the animal’s fur and soft tissue are also fossilized. There are clear impressions of both hair and underfur, along with hair-related skin structures.

Interestingly for Australians, this wee beastie has ankle spurs and was “probably” an egg-layer.

The history of mammals, it seems, grew by 40 million years practically overnight. And if this little guy (with flattened bones specialised to swimming and fully developed fur) is 164 million years old, his less-specilised ancestors would have to be even older, so we’re probably on the hunt for mammals or near-mammals down near (or in) Triassic strata now.

Interesting times, indeed.

No comments: