Study author Jacqueline Lungmus, a research assistant at Chicago’s Field Museum and a doctoral candidate at the University of Chicago said: “Aside from fur, diverse forelimb shape is one of the most iconic characteristics of mammals.
“We were trying to understand where that comes from, if it’s a recent trait or if this has been something special about the group of animals that we belong to from the beginning.”
In spite of this, the earliest synapsids, called pelycosaurs, looked like massive bulking lizards, but they are in fact more closely related to us than they are the dinosaurs.
Study co-author and Field Museum curator Ken Angielczyk, said: “If you saw a pelycosaur walking down the street, you wouldn’t think it looked like a mammal – you’d say, ‘That’s a weird-looking crocodile.'”