New Fossil From Brazil Hints at Origins of Early Triassic Reptile

Life restoration of Elessaurus gondwanoccidens, from the Sanga do Cabral Formation (Lower Triassic), Brazil. (Artwork by Márcio L. Castro)

(CN) — A new species of a Triassic reptile has been discovered in Brazil, and paleontologists confirm it is a close cousin of the mysterious lizard-like group called the tanystropheids, according to a new study.

Reptiles are known to have dominated global ecosystems following the Permian mass extinction about 250 million years ago. It was the worst extinction event Earth has seen, destroying most of the synapsids — mammal-like reptiles — that flourished in that time and gave rise to the famous dinosaurs. 

“The beginning of the Lower Triassic is a period of extreme importance for the history of life, it was at this moment that the greatest known mass extinction happened,” said lead author Tiane De-Oliviera of the Federal University of Santa Maria, Brazil, in an email. “After this extinction, the reptiles took over the global ecosystems. Tanystropheids are among the first lineages that emerged after this extinction.”

Evidence shows that immediately after the decimation of 90% of all species, medium- and large-sized reptiles actually began walking upright with their legs tucked underneath them as modern animals do, as opposed to sprawled out on either side of them the way modern lizards do, which would have contributed to their increased success. They thrived and diversified after this event, giving rise to the tanystropheids, a strange group of long-necked animals that remain a mystery to scientists today. 

The reptiles’ necks accounted for about half their length and were roughly as long as the modern green anaconda. In fact, their necks were so unusually long that when the first tanystropheid was discovered in the 1800s, paleontologist Francesco Bassani suspected that the semiaquatic creature was instead a flying reptile and the long neck was a wing. They are sometimes affectionately referred to as the weirdos of the Triassic.

They weighed in at an estimated 300 pounds and sported four webbed feet, an evolutionary feat developed as they probably spent most of their time near bodies of water catching fish. Interestingly, their front legs were notably shorter than their rear legs, leading scientists to believe they often shifted their weight forward to reach their necks over water and catch fish. They had exceptional muscle strength toward their rear end, giving them increased control and balance when maneuvering their long necks, though they would not have been expert swimmers and most likely walked along the floors of rivers and lakes. 

Aside from the knowledge that they were adept at fishing, further evidenced by their long, conical teeth ideal for catching marine prey, they’re everyday lifestyles remain unknown. It was first suspected that the creatures were fully aquatic, then semiaquatic as new evidence presented itself, though more is needed for a solid conclusion.

“The lifestyle of this group is still very controversial. We believe that tanystropheids or close relatives, as Elessaurus, were able to inhabit a wide range of climatic conditions,” De-Oliviera said. “Some tanystropheids possibly inhabited terrestrial or semiaquatic habits, whereas more specialized forms may have been fully aquatic.” 

Nevertheless, all discoveries indicate the tanystropheids were successful during the Triassic period. Adequately preserved remains of these creatures from the Early Triassic period are extremely rare, leaving paleontologists fascinated but with a poor understanding of this group’s early evolution.

In a study published Wednesday in the open-access journal PLOS One, author Tiane De-Oliviera of the Federal University of Santa Maria, Brazil and her colleagues discuss their findings on a new specimen of reptile found in Early Triassic rocks from the Sanga do Cabral Formation in southern Brazil, a significant location for discovering fauna of the Mesozoic era. Further analysis and skeletal comparison suggest the reptile, characterized from remains of the hind leg, pelvis and tail, is now the closest known relative of the tanystropheids.

The researchers named the new species Elessaurus gondwanoccidens. The name comes in part from the Elvish name, Elessar, of a character from Lord of the Rings who is also known as Aragorn or Strider, chosen as a reference to the fossil animal’s long legs. The second part of the name comes from the ancient supercontinent of Gondwana, which broke up about 180 million years ago and is where these enigmatic specimens inhabited.

The majority of tanystropheid fossils have been found in Middle to Late Triassic rocks of Europe, Asia and North America, and often in marine sediments. Scientists found the Elessaurus in continental deposits of Early Triassic South America, indicating the origins of the species might have been in the southern continents. 

Furthermore, this discovery suggests that Elessaurus’ ancestors could have lived on land before the later evolved species adapted to aquatic life.

“The new specimen was collected in a depositional environment of ephemeral fluvial systems in an arid landscape, quite distinct from the marine deposits where tanystropheids are usually found,” De-Oliviera said. “We propose a terrestrial lifestyle for Elessaurus, however, inhabiting the vicinities of shallow waters and low-sinuosity river environments, based on both morphology and the environment described for the locality where the new specimen was found.”

While these findings hold valuable information about these mysterious reptiles, the authors note that a clearer view of the group’s origins will rely on more rare fossils from this early time in their evolution.

“This work is very important to help to understand the origin of representatives of Archosauromorpha after the greatest of all extinctions already described,” De-Oliviera said. “Elessaurus gondwanoccidens may represent one of the oldest Tanystropheidae-related archosauromorphs to this date.”

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