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A fanged marine reptile that wandered the oceans 240 million years ago had an “underwater float”.
Scientists say the two-footed creature used a short, flat tail to balance itself as it hid near the bottom of the shallows, picking up fish with its razor-sharp teeth.
He also had excellent hearing, to help him avoid giant sea monsters in search of a tasty snack.
The bizarre creature today lived like seals, taking food in the water but coming ashore on rocks and beaches.
It belonged to a group of Triassic animals called nothosaurs that had long necks and normally an even longer tail used for propulsion.
Lead author, Dr Qing-Hua Shang, of the Chinese Academy of Sciences in Beijing, said: “Our analysis of two well-preserved skeletons reveals a reptile with a large, densely bony body and a very short, flattened tail. “.
(Image: Tyler Stone / SWNS.COM)
The fossilized bones were unearthed from thin layers of limestone in two quarries in southwestern China.
Dr Shang said, “A long tail can be used to slide through the water, generating thrust.
“But the new species was probably better suited to staying close to the bottom in a shallow sea, using its short, flattened tail for balance, like an underwater float, allowing it to conserve energy while hunting for prey.”
The unusual feature helped identify Brevicaudosaurus jiyangshanensis as a new species. The first word is Latin for “short-tailed lizard”.
It also had a small head, fangs, fin-like limbs, and a long neck, just like other notosaurs.
The most complete specimen was excavated in the Jiyangshan quarry, proving the second part of its name.
It provides significant clues to the reptile’s lifestyle. The forelimbs are more developed than the hind limbs, which suggests they played a key role in helping him swim.
(Image: QING-HUA SHANG, XIAO-CHUN WU e)
But the bones in the front legs are short compared to other species, limiting the power with which it could pull through the water.
Most of its bones, including vertebrae and ribs, are thick and dense, which further contributes to its stocky and sturdy appearance.
This would have limited its ability to move rapidly underwater, but at the same time would have increased its stability.
Bones of high mass act as ballast. What the reptile has lost in speed, it has gained in being able to stay still.
They would have made it able to float neutrally in shallow water, balancing the force of gravity that would otherwise have caused it to sink.
Together with the flat tail, this would have allowed the predator to float motionless underwater, requiring little energy to remain horizontal.
Neutral buoyancy would also have allowed it to walk on the seabed in search of slow-moving prey.
Very dense ribs can also suggest that the reptile had large lungs, increasing the time it could spend below the surface.
As suggested by the lack of solid body weight support, the dinosaurs were not oceanic.
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But they had to come for oxygen. They had nostrils on the snout through which they breathed.
Brevicaudosaurus also had a rod-shaped bone in the middle ear called a stirrup, which was used for the transmission of sound.
This was generally lost in other fossilized notosaurs or marine reptiles during conservation.
Scientists had predicted it would be thin and thin. But in Brevicaudosaurus it is thick and long, which suggests 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 vigilant 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 in an age when reptiles ruled the oceans.
They included the legendary ichthyosaurs that could reach more than 80 feet in length.
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