A study published in the Journal of Vertebrate Paleontology stated that a 260-million-year old cow sized pre-reptile might be the first creature to walk on four legs. Morgan Turner, lead author of the study believed that the pre-reptile Bunostegos akokanensis was a sprawler (something like a modern lizard), but that was not the case.
Turner upon examining the fossil of Bunostegos akokanensis that was discovered between 2003 and 2006 in Niger came to the conclusion that the pre-reptile was not a sprawler. He concluded this by identifying Bunostegos akokanensis’ forelimb in which its anatomy is sprawling-precluding and directed underneath its body.
The study also allowed Turner and his colleagues to re-sketch Bunostegos akokanensis wherein the pre-reptile looked like a cow with a knobby skull and bony armour down its back.