Research spotlights crocodile evolution

HEFEI - More than 1,200 years ago, Han Yu, a Tang Dynasty (618-907) politician, issued a proclamation against the crocodiles living in a creek in South China.

After sacrificing a pig and a goat, Han, known for his exemplary prose style, read the proclamation asking the 6-meter-long predators to leave the area within seven days or he would show no mercy.

The area is now known as the Hanjiang River Delta - named after him - in Guangdong province.

Han has now been further recognized by a team of researchers from China, Japan and the United States studying partially fossilized remains of a crocodilian found in southeastern China. They have named the new species Hanyusuchus sinensis.

The researchers said it could serve as a missing link to settle debate on the crocodilian family tree.

Three families of crocodilians roam Earth today: sharp-nosed crocodiles, blunt-nosed alligators and lesser-known gharials, with thinner snouts.

The researchers studied crocodilian remains housed in four museums in Guangdong that were found at a dig site in southeastern China and labeled for years as crocodile skeletons.

According to the paper published in Proceedings of the Royal Society B, the researchers found Hanyusuchus sinensis shared some significant skull features with gharials and had a vocal structure only known in male Indian gharials. Carbon dating showed the bones dated back some 3,000 years, during China's Bronze Age.

Genetic evidence indicates that alligators were the first to split from the original crocodilian, followed by gharials and later crocodiles. While the timeline may go against intuition, because crocodiles and alligators resemble each other more than gharials, the researchers said that the new species is intermediate in body shape between gharials and the other two, filling the gap in the evolutionary tree.

The researchers also found chop marks on the skulls of Hanyusuchus sinensis, indicating that it had been killed or even beheaded by heavy bronze tools. Crocodilians play a key role in maintaining the freshwater ecosystems as top predators, they said, noting that humans were responsible for the extinction of Hanyusuchus sinensis about 300 years ago.

Liu Jun, from Hefei University of Technology, was the corresponding author of the research. He said crocodilian bones had been found at many archaeological sites in China and had been thought to belong to Chinese alligators. But the team's discovery could challenge that.

Liu said that as the only reptile feasting on humans in ancient China, Hanyusuchus sinensis may have even left marks on ancient Chinese civilization, such as legends about dragons.

In future studies, the researchers hope to extract ancient DNA samples from soft tissue preserved in the partially fossilized bones, which may provide a more accurate picture of the crocodilian family tree.