The 248-million-year-old fossil, which has been named Eohupehsuchus brevicollis, belongs to a group of mysterious early Triassic marine reptiles called hupehsuchians, which have so far only been unearthed in two counties in Hubei Province.
The 40-centimetre-long creature lived in a shallow inland sea, and was a distant cousin of the ichthyosaur.
"Probably the best living analogue for this marine reptile is the duck-billed platypus from Australia," says one of the paper's authors Professor Ryosuke Motani of the University of California Davis.
"Although it's a very different animal, it had a skull and beak like a duck without teeth, a very heavily built body with thick bones, and paddles to swim through the water. The details are different, but the general body design looks similar to a platypus."
Motani thinks the new species, described today in the journal PLOS ONE, probably lived on a diet of worms and shrimp, hence the unusual duck bill for sifting through sediments on the sea floor.
Unlike other hupehsuchians which have distinctive moderately long necks containing nine or ten cervical vertebrae, Eohupehsuchus brevicollis is the first member of the group to have a very short neck with only six cervical vertebrae.
The animal's skull is also different with a narrow forehead and parietal bones on the top of the head shifted back.
Ossification on the bones indicated this was a fully-grown adult member of its species rather than a juvenile.
The fossil was discovered in 2011 during a systematic excavation undertaken by the Geological Survey of China in the Yuan'an County in Hubei Province.
The nearly complete fossil is only missing the tip of the left forelimb which ended in a series of broken digits.
"The tip of the paddle is broken in a strange way, that could only have happened prior to burial," says Motani.
"It looks like the tip was bitten off by a predator, but the creature escaped and the wound healed.
"This small animal was living with much bigger predators reaching three metres or more, with big teeth, and they probably saw it as prey."
Hupehsuchians have been known about for half a century, however this new discovery shows they were far more diverse than previously thought with at least four species now known.
"We're finding many new specimens and surprisingly these bizarre-looking animals have a lot of diversity about them," says Motani.
Hupehsuchians lived just after the end Permian mass extinction event which peaked about 252 million years ago, killing off some 96 per cent of all marine life, and 70 per cent of terrestrial life on Earth.
"This was the planet's worst mass extinction event and it took a long time for the ecosystem to recover, so we were surprised to see so much diversity so soon after the mass extinction," says Motani.
Read more at Discovery News
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