Teleocrater rhadinus was an early crocodile-like dinosaur cousin

Teleocrater rhadinus reconstruction (Image by Gabriel Lio, and courtesy of Museo Argentino de Ciencias Naturales
Teleocrater rhadinus reconstruction (Image by Gabriel Lio, and courtesy of Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” in Buenos Aires)

An article published in the journal “Nature” describes a research about Teleocrater rhadinus, a carnivorous reptile that lived in the Triassic period, about 245 million years ago. A team led by Sterling Nesbitt of Virginia Tech studied specimens of this ancient cousin of the dinosaurs found in 2015 noting its similarities to crocodiles. However, this species and its other close relatives are the oldest of the group that originated dinosaurs and birds and this could greatly change the ideas about the early stages of their evolution.

Teleocrater rhadinus is a species that have been known for a long time since the first fossils were discovered in 1933 in Tanzania by paleontologist F. Rex Parringon. Unfortunately those were partial specimens and for decades paleontologists had an all too common problem having to try to classify this species without knowing some important features due to the lack of several bones. The result was that only in the ’50s these fossils were given a name following the study by Alan J. Charig.

The situation changed only in 2015 with the discovery of new specimens in the same area of ​​the first ones. Thanks to those new bones that include some lacking in the first specimens such as those of the ankles, it was possible for Sterling Nesbitt and his team to finish Charig’s work. The continuity between the two studies, even if separated by 60 years, is recognized by the fact that Charig is credited among the authors of the one published in “Nature”.

The researchers were able to establish that Teleocrater rhadinus is one of the oldest members of the group of archosaurs, which includes crocodiles, dinosaurs and birds. This could substantially change the ideas about the first dinosaurs and their relatives because so far generally paleontologists thought that they were bipedal chicken-sized creatures. Having established that a dinosaur cousin looked more like a crocodile and had a length between 2 and 3 meters (between 7 and 10 feet) is a surprising result.

Some other species of reptiles that lived in the Triassic in various parts of the world were studied in recent years as well and paleontologists had various problems in classifying them. Sterling Nesbitt himself studied one of these species, called Dongusuchus efremovi: for years this animal was excluded from the group of archosaurs but has now been included in the new group of archosaurs that includes Teleocrater rhadinus.

The discovery of various species of reptiles from the Triassic shows that at the time there was a difference among the ancestors of crocodiles, birds and dinosaurs. For a long time the scarcity of fossils from that era had forced paleontologists to resort to speculation regarding that phase of the evolution of archosaurs but now things are changing.

The study of Teleocrater rhadinus is not finished because the researchers intend to go to Tanzania to look for other fossils of this animal and perhaps of other species. Each new bone can potentially provide new important information to better understand the evolution of various groups of reptiles and the relationships between different species.

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