Dinosaurs coexisted with their predecessors, new study finds

A single grave containing the remains of both dinosaurs and lagerpetids, the creatures thought to have been precursors to their better-known cousins, suggests that the two families of reptiles may have coexisted for a short time, according to a newly published Current Biology study.

According to the Los Angeles Times and the Christian Science Monitor, University of Sao Paulo paleontologist Max Cardoso Langer and his colleagues discovered fossils belonging to two small dinosaurs and a pair of lagerpetids together at the Santa Maria Formation in southern Brazil.

Langer and his colleagues wrote that the discovery was “the first time nearly complete dinosaur and non-dinosaur dinosauromorph remains are found together in the same excavation… showing that these animals were contemporaries since the first stages of dinosaur evolution.” In fact, they believe that the two may have roamed the Earth together for nearly 30 million years.

“We previously thought that once dinosaurs appeared, they sort of out-competed and drove the other animals like lagerpetids to extinction… now we know that they were living side by side,” Langer told the Times. Both the newfound dinosaurs and the lagerpetid fossils were dated to be approximately 230 million years old, the study authors explained to the Monitor.

Fossils could reveal which traits are unique to dinosaurs

The two dinosaurs are believed to represent some of the earliest sauropodomorphs, and each of them could represent a new species known as Buriolestes schultzi, Langer explained to the media outlets. They would have been small, two-legged carnivores. The lagerpetids, on the other hand, were much smaller than their cousins and belonged to the species Ixalerpeton polesinensis.

“The new discovery confirms that the co-occurrence between non-dinosaurian Dinosauromorpha and dinosaurs was not restricted to later stages of the Triassic and to the northern parts of Pangaea, where silesaurids and lagerpetids have been found together with theropod dinosaurs, reinforcing rapid replacement as a very unlikely scenario for the initial radiation of dinosaurs,” the paleontologists wrote in their paper, which was published last Thursday.

Even though the bones were collected from the same location, Langer told the Monitor that “we cannot say” for certain that the two types of reptiles “were interacting… They could have died in different places and [their bodies] were transported to that spot and then they were buried.” Even so, the discovery shows that they did live in the same environment at the same time, he noted.

Furthermore, the researchers believe that Buriolestes schultzi may represent one of the earliest known types of sauropodomorphs, and that by comparing its bones to Ixalerpeton polesinensis, they might learn more about differences that arose as dinosaurs evolved and diverged from their ancestors, the Times reported. As Langer told the newspaper, this analysis may reveal “which characteristics are actually unique to dinosaurs and which appeared before in those precursors.”

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Image credit: Maurílio Oliveira

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