Fossilized pregnant reptile discovered in southern China

By | June 24, 2021

About 245 million years ago, 150 kilometers east of Kunming City in Yunnan Province, southern China, a pregnant Dinocephalosaurus died out. In February 2017, the long-necked, meat-eating marine animal and its fossilized embryo provided evidence that members of its animal group could give birth to live young. Previously, researchers thought that Archosauromorpha, ancient reptiles whose modern ancestors include crocodiles and birds, lay only eggs.

Paleontologist Liu Jun and his team at Hefei University of Technology in China published their analysis of the fossil animal last year (J. Liu et al. Nature Commune. 8, 14445; 2017). The specimen was one of 10,000 collected during 2008 at the Luoping Biota National Geopark, an area that long ago was covered in shallow water. Liu says that this is what helped preserve the fossil after it died.

Liu hopes the discovery will inspire other scientists to look for more evidence of live births in ancient reptiles, adding that studying fossils already excavated can be as useful as newly uncovered ones.

Finding examples. He cites a 2011 Science paper showing a live birth in a marine predatory plesiosaur, which went extinct about 66 million years ago. The plesiosaur specimen was excavated in 1987 in Kansas (F. R. O’Keefe & L. M. Chiappe Science 333, 870–873; 2011). “We need to do more work with older samples,” Liu says.

Liu said he received financial support from the China Geological Survey (CGS) and China’s National Natural Science Foundation. He suggests that although the level of science funding in China is extremely healthy, they may be linked to the craze of leadership figures. Former Chinese Prime Minister Wen Jiabao used to be a geologist. When Wen retired in 2013, “geological research and investment plummeted, with less and less funding from CGS”, Liu says.

Live birth is well known in mammals, where the mother has a placenta to nourish the developing fetus,” said Professor Aitchison.

“Live birth is also very common among lizards and snakes, where the babies sometimes ‘hatch’ inside their mother and emerge without the shelled egg.”

Until recently, it was believed that the third major group of living land vertebrates, crocodiles and birds (part of the wider group Archosauromorpha) lay only eggs.

“Indeed, egg laying is the primitive stage, which is observed at the base of reptiles and their ancestors such as amphibians and fishes,” said Professor Aitchison.

They said the new fossil was an unusual, long-necked marine animal called an archosauromorph that flourished in the shallow seas of South China in the Middle Triassic period.

The creature was a fish eater, sniffing its long neck from side to side to snatch its prey.

Its fossil was one of several surprisingly well-preserved specimens from new “Luping Biota” locations in southwestern China. There were no known fossils of this kind (marine vertebrates of this era) from Australia.

Lead author Professor Jun Liu from Hefei University of Technology China said the researchers were “excited” when they first saw this embryonic sample.

“We weren’t sure whether the fetal sample was the mother’s last lunch or her unborn child,” Professor Liu said.

“Upon further preparation and closer inspection, we found something unusual.”

He said that the fetus was inside the rib cage of the mother, and it was facing forward; Swallowing animals typically face backwards as the predator swallows its prey’s head—first helping it move down its throat.

Furthermore, the tiny reptile inside the mother was an example of the same species.

“Further evolutionary analysis revealed the first case of live birth in such a wide group comprising birds, crocodiles, dinosaurs and pterosaurs, and pushed back evidence of reproductive biology in the group by 50 million years,” Professor Liu said.

“Information on the reproductive biology of archosauromorphs prior to the Jurassic period was not available until our discovery, despite the group’s 260-million-year history.”