Pangaea, a single supercontinent existing from 300-200 million years ago, dominated the Earth during thePermian era with animal and plant life dispersed broadly across the land. This disbursement is documented by identical fossil species found on multiple modern continents.
A new study, from the Society of Vertebrate Paleontology, supports the idea that Pangaea had an isolated desert at the center of the supercontinent with unique fauna.
A very distinctive creature known as a pareiasaur roamed the desert in what is now northern Niger. The large, herbivorous reptile was common across Pangaea during the Middle and Late Permian, approximately 266-252 million years ago.
“Imagine a cow-sized, plant-eating reptile with a knobby skull and bony armor down its back,” said Linda Tsuji of the Burke Museum and Department of Biology at the University of Washington. The newly discovered fossils belong to the aptly-named genus Bunostegos, which means “knobby [skull] roof.”
Though most pareiasaurs had bony knobs on their skulls, the Bunostegos had the largest, most bulbous knobs ever discovered. Scientists believe these bony knobs were probably skin-covered horns, much like those on modern giraffes. Such features seem to suggest that Bunostegos was an evolutionarily advanced pareiasaur, however it had many primitive characteristics as well.
The team’s analysis reveals Bunostegos was actually more closely related to older and more primitive pareiasaurs. This led the team to make two conclusions. First, the knobby head of the Bunostegos was the result of convergent evolution, and second, the genealogical lineage of this animal had been isolated for millions of years.
Fences were not required to isolate this population of cow-sized reptiles. Instead, they were fenced in by climatic conditions that kept them, and several other reptiles, amphibians and plants constrained to the central region of Pangaea.
“Our work supports the theory that central Pangaea was climatically isolated, allowing a unique relict fauna to persist into the Late Permian,” said Christian Sidor, also of the Burke Museum.