With a weird knobbly face and look like a cross between a lounge lizard and a river horse , this pre - reptileis now thoughtto be the earlier known animal to have walked upright on all fours . Know asBunostegos akokanensis , it lived about 260 - million - years ago , plodding around what is now the African res publica of Niger . Belonging to a mathematical group of creature called pareiasaurs , some debate that they finally gave cost increase to turtles , though this is debated .
“ A lot of the animals that lived around the [ same ] time had a interchangeable upright piano or semi - vertical hind limb posture , but what ’s interesting and special aboutBunostegosis the forelimb,”explainsMorgan Turner , who co - authored the paper published inThe Journal of Vertebrate Paleontology . “ The element and feature within the forelimb bone wo n’t allow a sprawling posture . That is unique . ”
It was antecedently thought that at the timeBunostegoswas stomp around Pangea , the supercontinent that split up to form the Continent we have intercourse today , all pareiasaurs move with a “ sprawling ” pace . This is when the animal ’s limbs baffle out from the side of the body and then pitch down to pip the flooring , as see in modern - day lizards and salamanders . It is the most rude form of motive power on land , occurring before animals evolve a full erect stance .
Now , it appears that passage happened earlier than antecedently thought . Originally discovered in 2003 , the fossils ofBunostegoscaught the eye of paleontologists atBrown University . When look at the forearms of several individuals , and the joints between the bones , it became more and more apparent to Turner that the animals ’ limbs must have been positioned directly below the body .
The shoulder articulation ( 1 ) , humerus ( 2 ) , human knee - like elbow joint ( 3 ) , and a longer low sleeve ( 4 ) together make the shell that Bunostegos stood with its wooden leg under its consistency . Morgan Turner / Brown University
The shoulder joint junction is at such an slant that it would have been physically impossible for the humerus , or upper sleeve bone , to have stuck out sideways . In addition to this , while the humerus of most sprawling animals is wrick – to allow the lower weapon system and understructure to attain the floor – this is not seen in the bones ofBunostegos , indicate that it was not put in the same way . And the evidence does n’t terminate there .
The elbow joint joint in most sprawling pareiasaurs is incredibly flexible , but Turner did not find that to be the case inBunostegos . Instead , the joint was a lot more similar to our human knee joints , only allowing for a forward and backwards motion of the lowly sleeve and foot . eventually , confirming the conclusion in Turner ’s opinion were the proportional lengths of the upper and lower arm , with the latter being longer than the former , as is mutual in most non - sprawling animal .
“ Posture , from sprawling to upright , is not blackened or clean , but or else is a gradient of forms,”saysTurner . “ There are many complexities about the phylogenesis of strength and locomotion we are working to better interpret every day . The frame ofBunostegosis unexpected , illuminating , and tells us we still have much to pick up . ”
Because of this gradient , Turner expects there were belike other pareiasaurs inhabit at the clip with a similar pace toBunostegos , but are yet to be found .
