Chelonoidis

Chelonoidis is a genus of tortoises, family Testudinidae, order Testudines, formally established by the Austrian zoologist Leopold Fitzinger in 1835 and comprising four living species found across South America and the Galapagos Islands, including the red-footed tortoise, the yellow-footed tortoise, the Chaco tortoise and the Galapagos tortoise with its several recognized subspecies. During the Pleistocene and Holocene the genus also had a wide distribution across the West Indies, though those island populations are now extinct. Chelonoidis tortoises are among the largest living land chelonians, and recent mitochondrial DNA analysis places the genus as most closely related to the lineage containing the genera Centrochelys and Geochelone. A notable ancestral adaptation let early members of the genus float with their heads held up and survive as long as six months without food or water, an ability believed to have enabled their ancestors to cross the Atlantic Ocean from Africa to South America during the Oligocene.