Chinese fossil of hammerhead marine reptile so weird its finders were ‘blown away’
Crocodile-sized plant eater dug up in Yunnan used its chisel-shaped teeth to scrape algae off rocks, scientists figure out after making model of its jaw using children’s clay and toothpicks
Two years ago, scientists in Yunnan province in southwest China found a peculiar-looking, beautifully preserved, 242-million-year-old marine reptile the size of a crocodile with a mouth like a zipper.
Nicholas Fraser, keeper of natural sciences at National Museums Scotland, says that he, along with Professor Li Chun, of the Institute of Vertebrate Palaeontology and Palaeoanthropology in Beijing, and Olivier Rieppel, a curator at the Field Museum in Chicago, puzzled over two newer specimens for 10 to 14 days before they had a breakthrough.
“We were blown away by how weird it was. We weren’t expecting to see anything like this … Although it’s well articulated, it’s still compressed a bit,” Fraser says. “So we went and bought some children’s clay…and we bought some toothpicks.”
That was the only way they could think of to figure out how the animal’s jaw worked. They realised that, unlike almost all other marine reptiles, this one, called Atopodentatus unicus, ate plants, making it the oldest herbivorous marine reptile in the fossil record. The only plant-eating marine reptiles alive today are green sea turtles and marine iguanas.
Fraser says the reptile has a hammerhead jaw with chisel-shaped teeth at the end. It would have scraped algae and similar plants off rocks in the sea, gulped them down along with water, and then used a sieve-like arrangement in its teeth to force the water out.
Fraser says: “The skull is pretty small, 10 to 12 cm … so this is a feeding machine, it’s grabbing the algae material, and it’s swallowing it, and it’s processing it down in the stomach and into the intestine, it is not doing any processing of the food in the mouth.”
Michael Pittman, a vertebrate palaeontologist and research assistant professor at the University of Hong Kong, calls it an “amazing fossil”.
He says the researchers could further prove the reptile ate plants by looking for algae preserved in gut specimens, studying how the teeth were worn down under an electron microscope, or studying the chemical make-up of the teeth (animals that eat plants have slightly different teeth from those that prey on other animals).
Fraser says scientists used to think it would have taken a long time for life to recover from a mass extinction, but this discovery adds to a growing body of evidence that there were many diverse forms of life around within six to eight million years after that mass extinction.
“That is not long in geological time, and certainly (in) evolutionary terms, this is actually a fairly short period,” he says. “This is just one more piece of evidence to indicate that life recovered relatively quickly.”
“We’re just starting to enter this period of research, so it’s exciting times.”