TURTLES & TORTOISES
The turtles & tortoises (Animalia, Chordata, Vertebrata, Reptilia, Anapsida, Chelonia) are an ancient group of reptiles that have a Triassic to Holocene stratigraphic record. Turtles are most easily recognized by their shell - some forms can retract the head & limbs into the shell when threatened, while other species cannot. Their overall body plan has changed very little since the Triassic - a great example of conservative evolution. Chelonians occur in terrestrial, freshwater, brackish-water, and marine settings.
Geochelone nigra - the Galapagos giant tortoise (mount). CM public display (Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, USA).
The largest living terrestrial chelonian on Earth is the Galapagos giant tortoise - Geochelone nigra (Quoy & Gaimard, 1824) (often referred to by the subjective junior synonym Geochelone elephantopus). It only occurs on islands of the Galapagos Hotspot in the eastern Pacific Basin. It is a long-lived, very slow-moving herbivore. Terrestrial chelonians tend to have shells of high convexity, presumably for protection from predators.
Malaclemys terrapin, the diamondback terrapin (captive) (above & below) from Chesapeake Bay, Maryland, USA. This species inhabits brackish-water settings of eastern and southeastern America (Gulf Coast & Eastern Seaboards areas).
Geochelone elegans (Schöpf, 1795) - the Indian star tortoise (captive). This terrestrial species occurs in peninsular India and Sri Lanka (a.k.a. Ceylon).
Chelodina longicollis - the snake-necked turtle (captive).
Macroclemys temminckii Troost, 1835 - the alligator snapping turtle (captive) (above & below). This large, heavy, freshwater aquatic turtle is a ambush hunter. It lies still on a substrate and uses a bright pink-colored, worm-like structure on its tongue to attract potential prey, such as fish. The jaws of this animal are exceedingly powerful.