Gharials in China's Bronze Age shine light on crocodilian evolution

HEFEI -- In 819 AD, Han Yu, a relegated politician from Tang Dynasty, issued a proclamation against the crocodiles living in today's Han River Delta in South China's Guangdong province.

After giving sacrifices of a pig and a goat, Han, known for his exemplary prose style in the ancient Chinese literature history, read aloud a "croc prose", asking the six-meter-long predators to leave the area within seven days or he would show no mercy.

More than 1,200 years later, an international team of researchers from China, Japan and the United States studied partially fossilized remains of the crocodilian found in southeast China, naming the new species after Han Yu -- Hanyusuchus sinensis.

The researchers said that Hanyusuchus sinensis could serve as a missing link to settle the debate on the crocodilian evolution family tree and may impact the knowledge of ancient Chinese civilization.

Three families of crocodilians are still roaming Earth today, namely sharp-nosed crocodiles, blunt-nosed alligators, and lesser-known gharials that are crocodile-like creatures with thinner snouts.

The researchers studied crocodilian remains housed in four museums in Guangdong Province. All the bones were found at a dig site in southeast 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 share 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 found that alligators were the first to split from the original crocodilian, followed by gharials and later crocodiles. While the timeline may go against intuition due to crocodiles and alligators resembling each other more than gharials, the researchers said that Hanyusuchus sinensis is intermediate in body shape between gharials and the other two, filling the gap in the evolution 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 weapons. Crocodilians play a key role in maintaining the freshwater ecosystems as top predators, said the researchers, noting that humans were responsible for the extinction of Hanyusuchus sinensis about 300 years ago.

Liu Jun from China's Hefei University of Technology is the corresponding author of the research. He said that crocodilian bones had been found in many archaeological sites in China. The bones were thought to belong to Chinese alligators, which today only live in east China's lower Yangtze River area. Their discovery could challenge this.

Liu said that as the only reptile feasting on humans in Ancient China, Hanyusuchus sinensis may have 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 evolution tree.