Dipsochelys is a genus of giant tortoise

Tortoise

Tortoises are a family of land-dwelling reptiles of the order of turtles . Like their marine cousins, the sea turtles, tortoises are shielded from predators by a shell. The top part of the shell is the carapace, the underside is the plastron, and the two are connected by the bridge. The tortoise...

 restricted to Madagascar

Madagascar

The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

 (extinct) and the Seychelles islands, containing six species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

:

• †Dipsochelys abrupta Grandidier 1868 - Madagascar, (extinct)
• Dipsochelys arnoldi Bour 1982 - Arnold's Giant Tortoise
  Arnold's Giant Tortoise
  Arnold's giant tortoise , also known as the Seychelles saddle-backed tortoise, inhabited the granitic Seychelles islands until around 1840, when it was presumed to be extinct, along with the Seychelles giant tortoise; a species which shared the same islands.The report of oddly-shaped of tortoises...
  
  , granitic islands of Seychelles, only in captivity
  Captivity (animal)
  Animals that live under human care are in captivity. Captivity can be used as a generalizing term to describe the keeping of either domesticated animals or wild animals. This may include for example farms, private homes and zoos...
  
  
• †Dipsochelys daudinii Duméril & Bibron 1835 - Daudin's Giant Tortoise, Seychelles, (extinct)
• Dipsochelys dussumieri Gray 1831 - Aldabra Giant Tortoise
  Aldabra Giant Tortoise
  The Aldabra giant tortoise , from the islands of the Aldabra Atoll in the Seychelles, is one of the largest tortoises in the world....
  
  , Aldabra
  Aldabra
  Aldabra, the world's second largest coral atoll, is in the Aldabra Group of islands in the Indian Ocean that form part of the Seychelles. Uninhabited and extremely isolated, Aldabra is virtually untouched by humans, has distinctive island fauna including the Aldabra Giant Tortoise, and is...
  
   atoll, Seychelles
• †Dipsochelys grandidieri Vaillant 1885 - Madagascar, (extinct)
• Dipsochelys hololissa Günther 1877 - Seychelles giant tortoise
  Seychelles giant tortoise
  The Seychelles giant tortoise has been thought to be extinct since the mid-19th century due to overexploitation on the granitic Seychelles islands. Similar giant tortoise species on other Indian Ocean islands such as Mauritius, Réunion and Rodrigues Island are also extinct...
  
  , granitic islands of Seychelles, only in captivity

Formerly these species were included in Geochelone

Geochelone

Geochelone is a genus of tortoises.Geochelone tortoises, which are also known as typical tortoises or terrestrial turtles, can be found in Africa and Asia. They primarily eat plants.The genus consists of three extant species:...

and sometimes included in the invalid genus Aldabrachelys

Aldabrachelys

Aldabrachelys is the currently recognised genus for the Seychelles and Madagascan radiations of giant tortoises, including the Aldabra giant tortoise...

.

The number of species within Dipsochelys has been a source of argument for many years with some authors suggesting that there is one highly variable species (Arnold 1979) and other views that up to 8 species occurred, of which only one or possibly two survive. This genus was found on Madagascar, the Comoros, Glorieuse, the Aldabra group (Aldabra, Assumption, Astove and Cosmoledo), Farquhar and the Seychelles group of islands. The only surviving wild population is on Aldabra (the species is known variously as Dipsochelys dussumieri, D. elephantina, Geochelone gigantea, Aldabrachelys gigantea or A. elephantina).

The Madagascan populations (D. abrupta and D. grandidieri) were extinct by about 1,000 A.D. Giant tortoises on the Comoros and Glorieuse are known only from fragmentary remains that are about 1,100 and 125,000 years old respectively. The Aldabra group, Farquhar and Seychelles retained wild tortoises until about 1830 when only captives of the species D. hololissa, D. arnoldi and D. daudinii survived. Genetic work completed in December 1996 has confirmed that two supposedly extinct species (D. arnoldi and D. hololissa) survive in captivity. Both species remain on the edge of extinction and are the subject of conservation work by The Nature Protection Trust of Seychelles.

Sources and references

• Arnold, E.N. 1979. Indian Ocean giant tortoises: their systematics and island adaptations.

PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY OF LONDON B BIOLOGICAL SCIENCES 286 (1011): 127-145

• Bour, R. 1984. Les tortues terrestres géantes des îles de l'océan Indien occidental. Studia Geologica Salamanticensia 1; 17-76
• Gerlach, J. 2004. Giant tortoises of the Indian Ocean. The genus Dipsochelys inhabiting the Seychelles Islands and the extinct giants of Madagascar and the Mascarenes. Edition Chimaira, Frankfurt, 208 pp.
• Gerlach, J. & Canning, K.L. 1997. Evolution and history of the giant tortoises of the Aldabra island group. Testudo 4(3); 33-40
• Gerlach,J. & Canning, L. 1998. Identification of Seychelles Giant Tortoises. Linnaeus Fund Research Report. Chelonian Conservation and Biology 3 (1): 133-135
• Gerlach, J. & Canning, K.L. 1998. Taxonomy of Indian Ocean giant tortoises (Dipsochelys). Chelonian Conservation and Biology 3 (1): 3-19

External links

• Further information on Seychelles giant tortoises
• 'Giant Tortoises of the Indian Ocean' by Justin Gerlach (Foreword by Sir David Attenborough)
• http://www.reptile-database.org/, http://www.reptile-database.org/db-info/taxa.html#C8, http://www.jcvi.org/reptiles/families/testudinidae.php The reptile database of the University of Heidelberg.