'Very Strange Animal' Was First Marine Plant Eater

An animal described as part Dr. Seuss, part dinosaur has been identified as being the first known plant-eating marine reptile.

The reptile, which lived 242 million years ago in southern China, arose after the planet's largest mass extinction, revealing that dire times can result in animals with seemingly improbable features.

The crocodile-sized plant eater, named Atopodentatus unicus, aka "Uniquely Strangely Toothed," is described in the journal Science Advances.

Senior author Nicholas Fraser of National Museums Scotland told Discovery News, "To me, it is very much in keeping with a Dr. Seuss creation!" said Senior author Nicholas Fraser of National Museums Scotland, adding that the Seuss tale, "The Things You Can Think" comes to mind.

Fraser and his team studied the fossils for the reptile, with a particular focus on what was previously thought to be a flamingo-like beak. The new analysis instead found that the "beak" was part of a hammerhead-shaped jaw apparatus that the reptile used to feed on plants on the ocean floor. Peg-like front teeth lined the jaw, which also had needle-shaped teeth. None of the teeth were suitable for eating meat.

Some sharks today have hammerheads, but their sharp teeth are definitely ready to sink into moving prey such as octopus and even other sharks.

Co-author Olivier Rieppel of Chicago's The Field Museum said that the marine reptile's peg teeth were used "to scrape plants off rocks on the seafloor, and then it opened its mouth and sucked in the bits of plant material. Then it used its needle-like teeth as a sieve, trapping the plants and letting the water back out, like how whales filter-feed with their baleen."

The teeth are reminiscent of those of certain dinosaurs, such as plant-eating Nigersaurus. The body of A. unicus seemed to be dinosaur-like as well, given the creature's long neck and rather chunky mid section.

While the lineage of A. unicus is a mystery for now, the researchers speculate that it was an "aberrant sauropterygian." These were aquatic reptiles that developed from terrestrial ancestors at around the time of the Permian-Triassic extinction event 252 million years ago. Sauropterygians include plesiosaurs that, like A. unicus, breathed air, had flippers and often long necks.

As for A. unicus looking somewhat like an underwater dinosaur, Fraser said, "Maybe all these large extinct animals seem so far-removed from anything we know today that we automatically try to group them together."

He said that after the big extinction event, there was a major breakdown in the food chain. Over a period of 6–7 million years, a large range of different feeding strategies had become established among marine reptiles. Some of these animals became suction feeders, while others feasted only on mollusks or fish. Still other strategies emerged, including A. unicus taking advantage of seafloor plant life.

Michael Benton, a professor of vertebrate paleontology at the University of Bristol, told Discovery News that A. unicus "adds to the amazing explosion of marine reptiles during the massive recovery of life from the Permian-Triassic mass extinction."

Xiao-Chun Wu of the Canadian Museum of Nature said, "The research is important not only for revealing the oldest record of herbivory with a bizarre head within marine reptiles, but also for us to understand the recovery mechanism of marine vertebrates, especially reptiles after the global extinction at the Permian-Triassic Transition."

Wu believes that further examination of the reptile's teeth using a highly magnified electronic microscope might reveal wear surfaces that could provide additional clues concerning what the animal was eating. He wonders if, instead of scraping off plants, A. unicus was "grabbing muddy piles with organisms, including algae and plant matter, which were shoveled together" in the mouth.

Read more at Discovery News