The FAQ of Metazooa contains a surprising fun fact: there is no reptile class in the game because “crocodiles are more closely related to birds than they are to lizards.”

To elaborate, according to evolutionary biologists, birds and crocodilians (crocodiles, alligators, and caimans) are both in the family “Archosauria”. They are the only remnants of this class since all the dinosaurs went extinct. But… crocodiles, birds, and dinosaurs are all pretty different, aren’t they? While they appear to have all had a common ancestor at some point, it turns out that a lot can change over 150 million years.

On one branch of the evolutionary tree, you have crocodiles (Metazooa Animal #175) which are sometimes called “living fossils” because they haven’t evolved much in millions of years. Meanwhile, birds started off as Theropoda, a clade of dinosaurs with hollow bones. These dainty-but-deadly creatures likely acquired feathers long before the ability to fly, but feathers serve many purposes: insulation, camouflage and protection, and aerodynamics, which was helpful when they weren’t flying yet but were running really fast.

As for dinosaurs, archaeologists and biologists examined their fossilised bones to find their place in the tree of life. They are placed in the archeosaur class, along with birds and crocs, because of the shapes of their skulls and vertebrae. So why did crocodiles and birds survive, but none of the other Archosaurs? No one really knows. But it’s possible that when an asteroid that hit the Earth off the coast Mexico 66 million years ago, smaller animals who could survive by flying or swimming had a better shot of making it to the modern era.

Would you like to see a dinosaur version of Metazooa? Reply to this email or let me know in the Discord!

Monday, January 22 to Sunday, January 28.

Degas, Edgar. Portrait of a Woman in Gray. 1865, oil paint on canvas, 91.4 x 72.4 cm. The Metropolitan Museum of Art, New York, accession no. 436152..

Play Forgeous for Jan 29.