Fossils Reveal a Hammer-Headed, Vegetarian Sea Weirdo

(c) Y. Chen, Institute of Vertebrate Paleontology and Paleoanthropology
(c) Y. Chen, Institute of Vertebrate Paleontology and Paleoanthropology / (c) Y. Chen, Institute of Vertebrate Paleontology and Paleoanthropology

The diversity on life on Earth today is wondrous to behold. So it’s not a huge surprise that prehistoric organisms were just as varied and bizarre. Paleontologists have identified the owner of some very strange fossilized remains: a crocodile-sized, hammer-headed, vegetarian sea reptile with peg-like front teeth. The researchers published their report today in the journal Science Advances.

The Middle Triassic species called Atopodentatus unicus ("unique, strange-toothed") was first unearthed and described in Wushan, China in 2014. At the time, researchers believed the animal’s fossilized remains showed evidence of a flamingo-like beak, which the ancient animal might have used to scoop up worms and other bugs from the sea floor. “It is obvious that such delicate teeth are not strong enough to catch prey,” the scientists wrote in their report, “but were probably used as a barrier to filter microorganisms or benthic invertebrates such as sea worms.”

Just one year later, another two Atopodentatus fossils emerged from a dig in Beijing. These fossils were in better shape than the first one, with clearly delineated jaws and snouts. But even with that extra material to work with, researchers still weren’t totally sure what they were looking at. So they got out the craft supplies.

Image Credit:(c) Olivier Rieppel, The Field Museum

“To figure out how the jaw fit together and how the animal actually fed, we bought some children’s clay, kind of like Play-Doh, and rebuilt it with toothpicks to represent the teeth,” co-author and Field Museum curator of evolutionary biology Olivier Rieppel said in a press statement. “We looked at how the upper and lower jaw locked together, and that’s how we proceeded and described it.”

Image credit: (c) Nick Fraser, National Museums Scotland

They realized that, rather than a beak, A. unicus’s face ended in a hammer-headed snout studded with peg-like teeth in the front and needle-like teeth in the back. With a vacuum-shaped face like that, the researchers say, Atopodentatus was probably more interested in Hoovering up water plants than digging for worms.

Image credit: (c) Y. Chen, Institute of Vertebrate Paleontology and Paleoanthropology

“It used the peg-like front teeth to scrape plants off of rocks on the sea floor, and then it opened its mouth and sucked in the bits of plant material,"Rieppel said. "Then, it used its needle-like teeth as a sieve, trapping the plants and letting the water back out.”

A number of sea creatures, including baleen whales, use filter-feeding systems, Rieppel continued, “but Atopodentatus is older than them by about eight million years.”

A. unicus’s age is important not just for this species, but as an indicator of the planet during its lifetime. The three fossils are around 242 million years old, which places the living animals on Earth not too long after a mass extinction event. “Animals living the years surrounding the Permian-Triassic extinction help us see how life on earth reacted to that event,” Rieppel said. “The existence of specialized animals like Atopodentatus unicus shows us that life recovered and diversified more quickly than previously thought."