Atopodentatus unicus is the most ancient herbivore marine reptile discovered so far

The skulls of Atopodentatus Unicus found in 2016 (Image W. Gao, Institute of Vertebrate Paleontology and Paleoanthropology)
The skulls of Atopodentatus Unicus found in 2016 (Image W. Gao, Institute of Vertebrate Paleontology and Paleoanthropology)

An article published in the journal “Science Advances” describes the analysis of fossils of Atopodentatus unicus, a reptile that lived in the mid-Triassic period, between 247 and 242 million years ago. Recent discoveries of two fossil skulls forced palaeontologists to rethink the idea they had made of this animal and now they consider it the most ancient herbivore marine reptile discovered so far.

The first nearly complete skeleton of Atopodentatus unicus, about 3 meters (10 feet) long, was discovered in 2014 in South China. Based on these fossils, it seemed that this reptile had a flamingo-like beak. However, the two skulls discovered in 2016 show that in fact the first specimen had a damaged skull and that this animal had a hammer-shaped head.

To better study Atopodentatus unicus mouth’s shape and use, the researchers used children clay to reproduce its jaws. Lately we got used to seeing in the field of paleontology the use of sophisticated technologies and therefore also of computers virtual reproductions of ancient animals. In this case, however, the study was carried out using simple methods that nevertheless allowed the researchers to see how this reptile’s jaws worked.

The conclusion of this exam is that Atopodentatus unicus was herbivorous. This reptile used its front teeth to scrape plants from the rocks on the sea floor and then suck in the plant pieces. Its needle-like teeth served as a sieve, trapping the plants and allowing water to flow out. It’s a technique similar to that used by whales with their baleen.

Putting together all the information, the researchers now think that Atopodentatus unicus was probably a semi-aquatic reptile. It shows some similarities to other Triassic marine herbivores but it’s a few million years older than them which makes it the most ancient discovered so far.

Atopodentatus unicus wasn’t a spectacular animal but it’s useful to paleontologists also to better understand the period of the world’s ecosystems rebirth after the devastating extinction at the end of the Permian period. it was a specialized reptile, showing that the evolution of the species that survived the extinction had already led to a new diversification.

A couple of years ago, a research suggested that shortly after that extinction there were already large predators in the oceans. The existence of species that filled certain ecological niches, in this case with a herbivorous reptile, in the mid-Triassic period also shows a quick life rebirth.

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