Fanged marine reptile had a short, flat tail that acted as an ‘underwater float’

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A marine reptile that lurked in the oceans 240 million years ago used its ‘short, flat tail’ as an underwater float to help it hide and pick off fish with its razor sharp fangs.

Researchers from the Chinese Academy of Sciences in Beijing say the reptile, a type of nothosaur, was about 2ft long, had excellent hearing and razor sharp teeth. 

The bizarre creature lived like modern seals – catching food in water but coming ashore to rest – and lives in an area that is now southwest China.

Nothosaurs were Triassic animals which had long necks and normally an even longer tail used for propulsion, but this creature is an unusual specimen due to its flat tail.

Lead author Dr Qing-Hua Shang and colleagues found two well-preserved skeletons , showing the dense boned body and a ‘very short, flattened tail’ buried in limestone. 

An illustration of Brevicaudosaurus. Researchers from the Chinese Academy of Sciences in Beijing say the reptile, a type of nothosaur, was about 2ft long, had excellent hearing and razor sharp teeth

An illustration of Brevicaudosaurus. Researchers from the Chinese Academy of Sciences in Beijing say the reptile, a type of nothosaur, was about 2ft long, had excellent hearing and razor sharp teeth

Lead author Dr Qing-Hua Shang and colleagues found two well-preserved skeletons , showing the dense boned body and a 'very short, flattened tail' buried in limestone

Lead author Dr Qing-Hua Shang and colleagues found two well-preserved skeletons , showing the dense boned body and a ‘very short, flattened tail’ buried in limestone

The fossilised bones belonging to Brevicaudosaurus jiyangshanensis were found in thin layers of limestone in two quarries in southwest China.

The unusual short, flat tail, allowed the team to determine that it was a new species, previously unknown to science and provided insights into different marine reptiles. 

Dr Shang said: ‘A long tail can be used to flick through the water, generating thrust.

‘But the new species was probably better suited to hanging out near the bottom in shallow sea, using its short, flattened tail for balance, like an underwater float, allowing it to preserve energy while searching for prey.’ 

It also had a small head, fangs, flipper-like limbs and a long neck – just like other nothosaurs previously discovered from the Triassic period.

The most complete specimen was dug up at Jiyangshan quarry – proving the second part of its name.

It provides remarkable clues to the reptile’s lifestyle. The forelimbs are more strongly developed than the hind ones, suggesting they played a key role in helping it swim.

But the bones in the front feet are short compared to other species, limiting the power with which it could pull through the water.

Most of its bones, including the vertebrae and ribs, are thick and dense, further contributing to its stocky, stout appearance.

This would have limited its ability to move quickly underwater – but increased its stability at the same time.

High-mass bones act as ballast. What the reptile lost in speed, it gained in managing to remain steady.

They would have made it neutrally buoyant in shallow water – balancing the force of gravity that would otherwise cause it to sink.

Along with the flat tail, this would have enabled the predator to float motionless underwater – requiring little energy to stay horizontal.

Neutral buoyancy would also have allowed it to walk on the seabed searching for slow-moving prey and highly dense ribs may have given it large lungs increasing time it could spend beneath the ocean surface searching for fish. 

Photographs and outlines of the skull and the mandible in dorsal view. Nothosaurs were Triassic animals which had long necks and normally an even longer tail used for propulsion, but this creature is an unusual specimen due to its flat tail

Photographs and outlines of the skull and the mandible in dorsal view. Nothosaurs were Triassic animals which had long necks and normally an even longer tail used for propulsion, but this creature is an unusual specimen due to its flat tail

As suggested by the lack of firm support of the body weight, nothosaurs were oceanic but they still had to come up for oxygen. 

They had nostrils on the snout through which they breathed.

The creature also had a bar-shaped bone in the middle ear called the stapes – used for sound transmission – that is often lost in fossilised remains during preservation.

Scientists had predicted it would be thin and slender. But in Brevicaudosaurus it is thick and long, suggesting it had good hearing underwater.

Co-author Dr Xiao-Chun Wu, of the Canadian Museum of Nature, said: ‘Perhaps this small, slow-swimming marine reptile had to be vigilante for large predators as it floated in the shallows, as well as being a predator itself.’

Brevicaudosaurus, described in the Journal of Vertebrate Paleontology, lived at a time when reptiles ruled the oceans including the 80ft long ichthyosaurs.  

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