The Devonian ancestors of fishes living today belonged to two main nonarmored groups. The cartilaginous fish, so-called because cartilage formed their skeletons, later gave rise to sharks and rays.

While the common ancestor of vertebrates with synovial joints is still a mystery, the oldest specimen with evidence of these ...

These synovial joints provide cartilaginous fish with remarkable mobility ... armored fish that dominated aquatic ecosystems in the Devonian period (359-419 million years ago).