Acanthomorpha (meaning "thorn-shaped" in Greek) is a huge taxon of teleost fishes with spiny-rays. The clade contains about one third of the world’s modern species of vertebrates: over 14,000 species. A key anatomical innovation in acanthomorphs is hollow and unsegmented spines at the anterior edge of the dorsal and anal fins. A fish can extend these sharp bony spines to protect itself from predators, but can also retract them to decrease drag when swimming. Another shared feature is a particular rostral cartilage, associated with ligaments attached to the rostrum and premaxilla, that enables the fish to protrude its jaws considerably to catch food.