''Aldabrachelys grandidieri'', or Grandidier's giant tortoise, is an extinct species of

tortoise Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like oth ...

that was

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

. Mitochondrial DNA extracted from subfossil bone confirm that it is a distinct species.

Description

''Aldabrachelys grandidieri'' was a

giant tortoise Giant tortoises are any of several species of various large land tortoises, which include a number of extinct species, as well as two extant species with multiple subspecies formerly common on the islands of the western Indian Ocean and on the ...

, one of the largest in the world, measuring about in carapace length. It was originally one of the six endemic

species of Madagascar (two large ''

Aldabrachelys ''Aldabrachelys'' is the recognised genus for the Seychelles and Madagascan radiations of giant tortoises, including the Aldabra giant tortoise (''Aldabrachelys gigantea''). Naming This name is problematic in that the type specimen is actually r ...

''; two medium ''

Astrochelys ''Astrochelys'' is a genus of tortoises in the family Testudinidae. The two species are both found in Madagascar, and both classified as critically endangered on the IUCN Red List The International Union for Conservation of Nature (IUCN) R ...

''; two small ''

Pyxis Pyxis is a small and faint constellation in the southern sky. Abbreviated from Pyxis Nautica, its name is Latin for a mariner's compass (contrasting with Circinus, which represents a draftsman's compasses). Pyxis was introduced by Nicolas-Lo ...

''). It is distinguished from all other ''

'' by a massive, flattened or depressed carapace, bulging sides of the carapace, short gulars, top of the nasal aperture is higher than the top of orbits, diverging quadrates, broad postorbitals, and a very large processus vomerinus dorsalis. It also had an unusually thick, strong carapace, possibly an adaptation to heavy predation. It seems to have been predominantly a grazer of meadows and wetlands.

Extinction

Material of this species has been dated to 1250–2290 years before present. It seems to have gone extinct relatively soon after the later migration of humans arrived from the mainland of Africa. Unlike its more common sister species, the abrupt giant tortoise ('' Aldabrachelys abrupta'' (also extinct)), the massive ''grandidieri'' did not seem to have succeeded in coexisting with humans for any length of time.

Ecology

''Aldabrachelys grandidieri'' (along with ''Aldabrachelys abrupta'') likely were seed dispersers of the six baobab (''

Adansonia ''Adansonia'' is a genus made up of eight species of medium-to-large deciduous trees known as baobabs ( or ). They are placed in the Malvaceae family, subfamily Bombacoideae. They are native to Madagascar, mainland Africa, and Australia.Trop ...

'' spp.) species endemic to Madagascar; in an experiment, extant

Aldabra giant tortoise The Aldabra giant tortoise (''Aldabrachelys gigantea'') is a species of tortoise in the family Testudinidae. The species is endemic to the islands of the Aldabra Atoll in the Seychelles. It is one of the largest tortoises in the world.Pritch ...

s (''Aldabrachelys gigantea'') readily consumed fruit of '' Adansonia rubrostipa''. Other ecological functions of giant tortoises likely included trampling and selectively consuming vegetation. It is suggested that introduced Aldabra giant tortoises could be used for restoration of these functions.

References

{{Taxonbar, from=Q4994646 Aldabrachelys Extinct animals of Madagascar Holocene extinctions Extinct turtles Fossil taxa described in 1868