Chelonoidis

Chelonoidis is a genus of tortoises in the family Testudinidae, distributed across the Americas, including the Galápagos Islands and mainland South America. The genus comprises a number of species, with the Galápagos giant tortoises forming the most famous group. In recent taxonomic work, island lineages formerly treated as subspecies or members of Chelonoidis nigra have often been recognized as distinct species within the genus, reflecting their long isolation and genetic differences. The mainland South American tortoises are also placed in Chelonoidis, with examples such as the Argentine tortoise (Chelonoidis chilensis) among them. The classification has evolved from earlier placements in Geochelone.

Description and ecology: Chelonoidis tortoises are large, terrestrial reptiles with heavy, domed shells and thick, pillar-like legs. They are predominantly herbivorous, feeding on grasses, leaves, fruit, and cacti, though diets can vary by species and habitat. They are known for long lifespans and slow reproductive rates, with females laying eggs in shallow nests and care typically limited to incubation and later guarding of young.

Habitat and distribution: Members of the genus inhabit a range of dry and humid environments across the Americas, from the arid and semi-arid zones of the Galápagos to various tropical and subtropical habitats on the mainland.

Conservation: Many Chelonoidis species face threats from habitat loss, invasive predators, overexploitation, and introduced diseases. The Galápagos tortoises have benefited from extensive conservation programs, including captive breeding and habitat restoration, while other species remain vulnerable or endangered.

See also: Galápagos Islands; List of Chelonoidis species.