From an analysis of the bones of Bunostegos akokanensis , a 260-million-year-old prereptile, experts believe it was the oldest known creature capable of getting on all fours. Until now, all known pareiasaurs that roamed the Pangea supercontinent in the Permian era 250 million years ago were crawlers whose limbs protruded from the body. Bunostegos akokanensis lived 260 million years ago when the continents that make up Earth today were still united into a supercontinent called Pangea. It had the look of a reptile and the size of a modern cow, with a lumpy skull and bony armor down its back.
It was discovered in Niger in 2003, and until now it was thought that it had been a crawler like the other pareiasaurs that lived in the same period. However, an analysis of his bones carried out by scientists at Brown University, Providence (Rhode Island) has determined that this was not the case. And it is that, contrary to the extremities of its contemporaries, which protruded laterally from the body and extended outward or leaned down from the elbow, those of the Bunostegos indicate that it walked upright on its fourth legs while moving to one side and the other. eating plants.
According to paleontologist Linda Tsuji, lead author of the study published in the Journal of Vertebrate Paleontology , pareiasaurids or pareiasaurs were large herbivores that reached their peak during the Middle and Upper Permian (between 266 and 252 million years ago) and that, to some researchers, would be relatives of the current turtles. Many of the fossils of pareiasaurids have been found in South Africa but they have also appeared in Morocco (Arganaceras), Scotland (Elginia), Germany (Parasaurus) or Russia (Deltavjatia, Scutosaurus and Orbirkovia).
Bunostegos akokanensis , the only pareiasaurid found in Niger, must have weighed about 272 kilos. Despite its large size, its head was proportionally very small and covered with lumps. The authors say that at first glance, the morphological characteristics of Bunostegos suggest that it was an advanced pareiasaurid, but it also has many primitive features that bring it closer to older pareiasaurids. Therefore, they conclude that its bulbous head was the result of a convergent evolution and that its genealogical lineage has been isolated for millions of years. Climate was the most likely cause that allowed both pareiasaurids and other reptiles, amphibians, and plants to remain isolated for millions of years.
