Bunostegos Possibly First Creature to Walk Upright on All Fours

Posted on September 17, 2015

Scientists say Bunostegos was possibly the first creature to walk upright on all fours. Bunostegos akokanensis is an ugly looking 240 million year old pre-reptile cow-sized creature. Researchers from Brown University analyzed the bones of the pre-reptile in the new study.

Pareiasaurs that roamed Pangea a billion years ago were described as sprawlers. They had limbs that jutted out from the side of the body and then either continued out or slant down from the elbow. Some modern lizards also have limbs that do this. The researchers found that Bunostegos had different forelimbs that other pareiasaurs. When analyzing the bones Morgan Turner, lead author of the study, was surprised to find Bunostegos was not a sprawler.

Turner says in a statement, "A lot of the animals that lived around the time had a similar upright or semi-upright hind limb posture, but what's interesting and special about Bunostegos is the forelimb, in that it's anatomy is sprawling-precluding and seemingly directed underneath its body--unlike anything else at the time. The elements and features within the forelimb bones won't allow a sprawling posture. That is unique."

Turner performed analysis of the Bunostegos bones while under the supervision of Professor Christian Sidor at the University of Washington. Turner is now a graduate student at Brown University. The bones were discovered in Niger by Linda Tsuji of the Royal Ontario Museum, Sidor and a team of paleontologists in 2003 and 2006.

Tsuji describes the creature as follows: "Imagine a cow-sized, plant-eating reptile with a knobby skull and bony armor down its back."

The researchers say Bunostegos's legs would have been beneath its body. The creature's glenoid fossa, humerus, eblow joint and ulna also indicate that the creature was not a sprawler. The researchers also say Bunostegos was an "isolated pareiasaur" and speculate that its upright posture might have helped it survive long journey's between meals in Niger's arid climate.

A research paper on Bunostegos akokanensis and its upright stance can be found here in the journal, Journal of Vertebrate Paleontology.

ANIMALS