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.




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