Convergent evolution is the idea, quite widespread in biology, that organisms can evolve similar features without being related.
Bird and bat wings are a good example: they evolved separately, and along very different branches of the vertebrate evolutionary tree, but look quite similar and serve the same purpose. There are lots of examples throughout nature, and likely throughout the fossil record as well. We’ve got some new proof of the latter, and it’s pretty interesting.
In the Great Depression, the Works Progress Administration was created to give people jobs working on infrastructure—building roads and parks all over the country. While at it, the WPA found a huge number of fossils, which were gathered up, protected, and sent to various universities and museums. A lot of them just sat in storage, and we find “new” species in those samples pretty regularly.
One such species, Triopticus primus, is a reptile with a very thick upper skull, not unlike the pachycephalosaur dinosaurs that would come along over 100 million years later. In fact, a number of species from the same era as Triopticus share some structural similarities with dinosaurs, despite living well before them.
“What we thought were unique body shapes in many dinosaurs actually evolved millions of years before in the Triassic Period, about 225 million years ago,” says paleontologist Michelle Stocker, one of the researchers.
In that era, a variety of reptile species had traits that dinosaurs would come to develop, in very different ecosystems and evolutionary contexts. What makes this convergent evolution is that the dinosaurs did not evolve from these reptiles. These species all died out, their traits with them, well before dinosaurs came along.
Convergent evolution is basically nature’s way of saying “there are only so many kinds of situations, and while evolution could develop unique ways to deal with them, it’s probably easier to just use what works when you can.”
“Triopticus exemplifies the phenomenon of body-shape convergence,” Stocker says, “because its skull shape was repeated by very distantly related dome-headed dinosaurs more than 100 million years later.”