What do birds, crocodilians, and dinosaurs share?

Beta-keratins, or beta-proteins, are rigid and waterproof structural proteins found in the epidermis of reptiles, birds, and pangolins. Fossil evidence confirms that dinosaurs like Sinosauropteryx possessed these proteins in their feathers, linking them to modern birds. Furthermore, crocodilians also possess similar beta-keratins, suggesting that these proteins evolved from common ancestral archosaur genes.

What we know

• Beta-keratins are structural proteins found in the epidermis of reptiles, birds, and pangolins, forming rigid and waterproof substances in scales, claws, and feathers. [2]
• Fossil feathers from the dinosaur Sinosauropteryx contain traces of beta-proteins, confirming an early composition similar to modern bird feathers. [3]
• Crocodilians possess beta-keratins similar to those of birds, suggesting the proteins evolved from common ancestral genes within archosaurs. [3]
• Beta-keratin is now scientifically classified as a beta-protein rather than a true mammalian-style keratin. [2]

Still open

• The exact extent to which feathers or feather-like structures were present across all dinosaurs as a whole remains a subject of ongoing research.

Where to go next

• what caused itHow did feathers evolve in dinosaurs?
• a case in pointWhat are the characteristics of crocodilians?
• how we knowHow are birds and dinosaurs related?
• the bigger pictureWhat is the role of the Archosauria group?
• whenHow did views on dinosaur physiology change over time?
• an unexpected connectionWhat do pangolins share with birds and reptiles?Pangolins surprisingly share the presence of beta-keratins in their epidermis with reptiles and birds, despite being mammals.

Sources

• [1]beta-keratin (Wikidata Q2930097) · CC0 1.0
• [2]Beta-keratin · CC BY-SA 4.0
• [3]Feathered dinosaur · CC BY-SA 4.0
• [4]Crocodylia · CC BY-SA 4.0
• [5]Physiology of dinosaurs · CC BY-SA 4.0