Geochelone abingdoni

(Günther, 1877)
Pinta (Abingdon) Island tortoise

The black carapace (to 98 cm) is shaped like a saddle, very narrow, compressed, and slightly upturned anteriorly, and wider and lower posteriorly with a rounded margin. The shell is rather thin and surprisingly light in weight. Only a slight cervical indentation is present. The height at the cervical indentation is 46% or more of the carapacial length. Vertebrals are usually broader than long, but the 1st is narrowed and may be as long as or longer than broad; the 5th is expanded. The surface of the vertebral and pleural scutes ranges from smooth to pitted. Eleven marginals lie on each side. Those anterior are serrated and slightly upturned, but their ventral surfaces are never completely vertical; the posterior marginals are slightly flared and downturned; the single, undivided supracaudal scute is downturned. Lateral marginals are vertical or downturned, and the 8th is wedge shaped with a very short, reduced, dorsal border. The black plastron is well-developed, but shorter than the carapace, and tapered (narrowed) anteriorly and posteriorly. At best, only a slight anal notch is present. The plastral formula is: abd > hum > fem > gul >< an > pect; the paired gular scutes do not project beyond the carapacial rim. The bridge is narrow (43-45% of carapace length) with single small axillary and inguinal scutes of the same size. The head is small with a nonprojecting snout and a weak bicuspid upper jaw. Its divided prefrontal scale is small, as is the single frontal scale. Head, neck, limbs, and tail are gray to black. The neck is very long with a biconvex 4th cervical vertebra. The anterior surface of each forelimb is covered with large, slightly overlapping to nonoverlapping scales. The short tail lacks a large terminal scale.
Males are larger than females, and have concave plastra, longer, thicker tails, and yellow jaws and throats.

Geochelone abingdoni is restricted to Pinta (Abingdon) Island, Galápagos.

Extremely rugged, as most of the island is covered with bare volcanic rock with numerous crevices and pits. Vegetation consists of scattered brushy thickets and Opuntia cacti.

Natural History
Specimens collected in 1906 had eaten grasses and cacti (Van Denburgh, 1914), a typical diet for Galápagos tortoises. Günther (1877) reported the anterior margins of the carapace were more or less broken, possibly as a result of male combat.

IUCN Red List Status (1996)
The entire Galápagos group (listed as Geochelone nigra) is considered Vulnerable (A2c, B1+2c). G. abingdoni (listed as Geochelone nigra abingdoni) is considered Extinct in the wild.
Thefuture of this species looks grim. Its [l][m]Glossary[/m][r]population[/r]population was apparently always small, and in 1959 goats were introduced to the island which destroyed much vegetation and drove the remaining tortoises from their lowland breeding areas. Females were seemingly also scarce, as only one has ever been collected (Pritchard, 1979). Today, only one individual, "Lonesome George", a captive male at the Charles Darwin Research Station on Santa Cruz Island, is known to exist (Caporaso, 1991), even though MacFarland et al. (1974a) thought a few may still remain in the wild. There now seems very little potential for the discovery of additional individuals on Pinta, even though nearly all goats have been removed (the few that appeared to have survived the eradication program will be removed in 1998; Linda J. Cayot, pers. comm.) and the island's flora has recovered considerably. The only apparent hope for survival of the species rests in discovery of one of more females in zoo collections or in backcrossing progeny resulting from females of the G. becki population (considered closest to G. abingdoni) with the sole Pinta male (Thomas H. Fritts, pers. comm.).
Recent examination of the mitochondrial DNA sequence of Lonesome George by Caccone et al. (1999) resulted in a startling discovery. Instead of his DNA closely matching that of tortoises from the nearest island Pinta, it showed more similarities with the DNA Geochelone chathamensis from San Cristóbal and G. hoodensis from Española, the most distant islands from Pinta (Galápagos). His DNA also matches that of three tortoises collected on Pinta in 1906, so he truly is the last survivor of that population and not a more recent transplant. DNA from the three other Pinta tortoises also most closely match the San Cristóbal and Española tortoises. How these tortoises reached Pinta is unknown, possibly they were carried there by mariners. Attempts to breed Lonesome George with females from nearby islands has failed, as he has showed little interest in them, possible additional evidence that speciation has occurred among the various island populations of tortoises. Females from San Cristóbal and Española should be introduced to Lonesome George to see if he is interested in breeding.