A Common Ancestor Of Dinosaurs And Pterosaurs Found In Madagascar
Paleontologists have found the remains of a miniature lizard, which was a relative of both dinosaurs and pterosaurs in the deposits of the Triassic period in Madagascar. The scientific journal Proceedings of the National Academy of Sciences published a description of the find.
"We used to think that almost all dinosaurs were huge. We found the remains of a creature that is evolutionarily close to both dinosaurs and pterosaurs, and at the same time was very small," said Christian Kammerer, one of the authors of the work, curator of the Museum of Natural Sciences of the state of Carolina (USA).
According to modern paleontologists, pterosaurs were the first vertebrates to learn flight. Contrary to common beliefs, they are not dinosaurs at all or even their close relatives. As scientists suggest, these winged lizards appeared at the end of the Triassic period, about 220-210 million years ago, a few tens of millions of years after their ancestors, similar in appearance to lizards, separated from the common tree of evolution of archosaurs.
Where and how they evolved, paleontologists can not yet say. Some scientists suggest that pterosaurs were originally aquatic or semi-aquatic creatures and learned to fly gradually. This hypothesis is supported by the structure of their clutches and eggs. Other researchers doubt this.
Thanks to excavations in the South-West of Madagascar, where rocks of the mid-and late Triassic period formed about 240-230 million years ago, Kammerer and his colleagues took a big step to learn the history of these flying lizards.
The quirks of evolution
Scientists found a lot of fossils there two decades ago and spent all the subsequent time studying them. Recently, paleontologists noticed that among these remains were the bones of a small and unusual lizard that belonged to the so-called ornithodir, a special category of archosaurs, which included both dinosaurs and pterosaurs.
The length of the reptile did not exceed ten centimeters, and the mass – several tens of grams. After analyzing its anatomy, Kammerer and his team concluded that this lizard is the most primitive known relative of both dinosaurs and pterosaurs. It was named Kongonaphon Kely, which means "little insect killer" in a mix of ancient Greek and Malagasy.
This creature was significantly smaller than the older archosaurs, which suggests that the original evolution of both dinosaurs and pterosaurs was not in the direction of increasing size, but in the direction of miniaturization.
Scientists suggest that the small size and insect-based diet helped the ancestors of dinosaurs and pterosaurs coexist with the giant crocodile-like ravisuchia, four-legged predators that could reach six meters in length and several hundred kilograms in weight. According to Kammerer and his colleagues, the transition to this ecological niche, which was empty before the appearance of ornithodir, played a key role in the evolution of both dinosaurs and pterosaurs.
In particular, their small size helped the ancestors of both lizards survive the unstable climate of the Triassic period and several mass extinctions that wiped out ravisuchus and other large archosaurs. Also, miniaturization allowed pterosaurs to take the first steps towards flight and become the first flying four-legged creatures, the researchers conclude.