Scientists Discover Ancient Marine Predator With a Built-In Float

Brevicaudosaurus jiyangshanensis, gen. et sp. nov., skeletons in dorsal view. (Qingq-Hua Sang, Xiao-Chun Wu and Chun, Journal of Vertebrate Paleontology)

(CN) — Scientists confirmed the discovery of a 240 million-year-old aquatic lizard with an affinity for shallow seas, where it used its short flat tail as a float while it hunted.

The lizard, named Brevicaudosaurus jiyangshanensis, was described in the Journal of Vertebrate Paleontology Wednesday as a Ladinian nothosauroid.

The genus Brevicaudosaurus comes from Latin meaning short-tail lizard. The species name jiyangshanensis refers to the place where it was discovered: the Jiyangshan Quarry near the Huangnihe River in southwestern China’s Guizhou Province.

“The new species we’ve identified 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,” explained Qing-Hua Shang from Beijing’s Chinese Academy of Sciences in a statement.

“Our analysis of two well-preserved skeletons reveals a reptile with a broad, pachyostotic (denser boned) body and a very short, flattened tail,” Shang said.

Paleontologists from the Chinese Academy of Sciences and the Canadian Museum of Nature in Ontario collaborated on this project.

Researchers estimate the 23-inch specimen to be fully grown, though judging by the unfused bones it may have been a young adult or juvenile.

With four sharp fangs among an unknown number of teeth and four flipper-like limbs, the carnivore likely hunted its prey along the bottom of the sea.

Like other aquatic reptiles from the Triassic period, B. jiyangshanensis had thickened bones, a process known as pachyostosis, which might have made the animal neutrally buoyant. The short flat tail referenced in its name also likely helped it maintain balance in the water column. Both of these attributes helped B. jiyangshanensisstabilize itself in the water — but slowed down its swimming speed.

An illustration of Brevicaudosaurus. (Art by Tyler Stone, BA ’19, art and cinema; see his website https://tylerstoneart.wordpress.com)

“Highly dense ribs,” indicate B. jiyangshanensishad large lungs that allowed it to remain underwater for long periods of time between trips to the surface to breathe through snout nostrils.

Researchers found a surprise in the inner ear of B. jiyangshanensis. Where researchers expected to find a thin bar-shaped bone called stapes, they instead found stapes that are long and thick, indicating this lizard may have been able to hear well underwater — another attribute needed to help a slow swimmer survive.

“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,” said the study’s co-author Xiao-Chun Wu from the Canadian Museum of Nature in a statement.

Researchers classified B. jiyangshanensisas a member of the extinct aquatic nothosauroid reptiles, recognized by their large powerful flippers that thrived in the Mesozoic seas. While it appears the European pachypleurosaurs may be related to China’s nothosauroidea and pistosauroidea, the exact relationships remain poorly understood.

With another piece of the puzzle in place, researchers hope this species helps test other ancient phylogenic relationships.

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