New fossils of an ancient reptile called Bunostegos akokanensis indicate that it probably wasn’t winning any prehistoric beauty contests.
“Imagine a cow-sized, plant-eating reptile with a knobby skull and bony armor down its back,” Linda Tsuji, leader of a new study on the critter, said in a statement. (Also see “Pictures: Oldest Reptile Embryos Discovered.”)Bunostegos akokanensis is seen in an artist’s rendering. Illustration courtesy Marc Boulay
But the specimens, discovered in northern Niger, are giving the University of Washington’s Tsuji and colleagues a glimpse into the Middle and Late Permian periods (266-252 million years ago), when all of Earth’s landmasses were joined into a single supercontinent called Pangaea. (See a prehistoric time line.)
B. akokanesis belonged to a group of large reptiles called pareiasaurs that were common across Pangaea. The new Niger specimens show that species in the genus Bunostegos were related to older, more primitive pareiasaurs, according to an analysis published June 25 in the Journal of Vertebrate Paleontology.
Their ancient position in the pareiasaur family tree suggested that the Bunostegos lineage was isolated for millions of years. And since Bunostegos are some of the knobbiest pareiasaurs, this also meant that the bumpy heads that characterized other lineages in this group evolved independently of each other.
Since Bunostegos didn’t intermix with other pareiasaurs, the team reasoned that the genus had to be geographically isolated. Their theory: That an extreme desert in what’s now northern Africa essentially sequestered the creatures in one region.
During their isolation, the reptiles evolved all kinds of new adaptations, including their skin-covered horns. Over time, the horns became the most bulbous of all the pareiasaurs. (Also see “New Horned Dinosaurs Found—Among Littlest Known.”)