Tortoises (/ˈtɔr.təs.ɨz/) are a family, Testudinidae, of land-dwelling vertebrates in the order Testudines. Tortoises are shielded from predators by a shell. The top part of the shell is the carapace, the underside is the plastron, and the two are connected by the bridge. The carapace is fused to both the vertebrae and ribcage, and tortoises are unique among vertebrates in that the pectoral and pelvic girdles are inside, rather than outside, the ribcage.