“If you look at a dog or cat claw, they’ve got like a bony claw underneath that keratin sheath, right? So, it’s the same with a dinosaur,” Zelenitsky said. Keratin, a protein that helps make up ...

Two claws, they note, would have made each claw stronger than if there were three, allowing the dinosaur to grab thicker branches. More information: Yoshitsugu Kobayashi et al, Didactyl ...