How the shark forgot his skeleton

Bony skeletons may be even older than palaeontologists thought

Sep 10th 2020

VERTEBRATES—THOSE animals with a backbone—are a diverse bunch, encompassing everything from tuna and budgerigars to snakes, chinchillas and human beings. One way biologists divide them up concerns the composition of their skeletons. Most vertebrates sport hard, calcified bones, and are dubbed the osteichthyans. A second, much smaller category is the chondrichthyans, whose members include sharks, rays and skate. Unlike their hard-boned cousins, chondrichthyans make do with structural parts made of soft, tough cartilage.

This article appeared in the Science & technology section of the print edition under the headline “Bones of contention”