3 November 2020

Since the 1980s scientists have known that birds are highly specialized dinosaurs that survived the K-T extinction 66 million years ago. Dinosaurs were reptiles. Therefore so are birds. Who among the reptiles is the bird’s closest relative?

The cladogram below shows how mammals and reptiles had a common “stem reptile” ancestor. However, during the Carboniferous period mammals diverged from the rest of reptiles and became very different (left branch).

During the Permian, Turtles diverged from the rest of the reptiles. Later the Archosaurs did, too (far right branch). Some of the Archosaurs resembled crocodiles.

Crocodiles didn’t change much in the past 80 million years.

But dinosaurs changed a lot and the Theropod dinosaurs became birds!

These unlikely relatives reunite at the St. Augustine Alligator Farm Zoological Park where wild birds nest in the trees above the crocodiles.

(photos from Wikimedia Commons, diagram derived from Creative Commons licensed cladogram; click on the captions to see the originals)