Meet Bunostegos Akokanensis, the First Creature to Walk Upright on all Fours

A pre-reptile that looks like a cross between a modern lizard and a hippo is believed to be the earliest known creature to walk on all fours, according to new research from Brown University.
As it roamed Pangaea 260 million years ago, the cow-sized herbivore Bunostegos akokanensis stood out -- quite literally -- from its peers, which were best described as "sprawlers," creatures whose limbs extended out from the side of their body, pointing sideways instead of downward.
In 2003, however, a B. akokanensis specimen's unique shoulder and elbow joints tipped paleontologists off to the creature's unexpected posture.
"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 its anatomy is sprawling -- precluding and seemingly directed underneath its body -- unlike anything else at the time," study lead author Morgan Turner said in a news release.
"The elements and features within the forelimb bones won't allow a sprawling posture. That is unique."
According to researchers, walking upright is more energy efficient than sprawling. In an area where food and water were hard to come by, those energy savings could have proved crucial to B. akokanensis' survival.
Turner's research is published in the Journal of Vertebrate Paleontology.