No mammal may be more perplexing than the platypus.

Attached to its furry, otter-like body are four webbed feet, several sharp claws, a beaver tail and, of course, that iconic duckbill. The females lay eggs and males sport venom-secreting spurs on their hind legs. One could only imagine how dumbfounded the first people to stumble upon these creatures were.

But if you were to wager a guess, they probably had a similar expression to that of Ryosuke Motani when he initially encountered the fossilized remains of the extinct marine reptile called Eretmorhipis carrolldongi.

Like the platypus, this recently discovered prehistoric creature had a duckbill. But then nature made it even weirder, adding plates on its back like a stegosaurus, a long tail like a crocodile, large paddle-like limbs and a tiny head with teeny eyes.

“It’s a pretty strange chimera of features,” said Dr. Motani, a paleobiologist at the University of California, Davis. “When I first saw it, I just said ‘What?!’ and didn’t speak for a while.”