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Artist's rendering of Geochelone sp. - Giant Tortise

Geochelone sp.
Giant Tortoise

Shell and partial skeleton
TMM 30967-2155
Freshwater pond deposit, Pleistocene
San Patricio County, Texas

Giant land tortoises like this specimen of Geochelone roamed the coastal plain of Texas during the Pleistocene.  Although this particular North American species is now extinct, having died out by about 10,000 years ago; it has living relatives on several islands of the world and on the mainland of Africa and South America.  Probably the most famous members of the tortoise family are the giant tortoises of the Galapagos Islands, which were studied by Charles Darwin as he developed his theory of evolution.  More distant and much smaller relatives of the giant tortoises still live North America, in the southwestern deserts, parts of Florida, and northern Mexico. 

Tortoises are part of a larger group of animals, the Testudines (turtles).  Most turtles are adapted for life in wetter environments like rivers, ponds, and the oceans of the world.  But tortoises are adapted to arid environments.  They are almost exclusively vegetarians, and they get all the moisture they need from the plants they eat.  They rarely if ever drink water.  In some settings they hibernate during the winters, while in other settings they are active most of the year.  In contrast to tortoises, most other turtles are carnivorous, eating fish, insects, grubs, worms, and carrion.  All tortoise species are threatened or endangered in the wild today. 

We are not sure what led to the extinction of giant tortoises in North America.  The change in climate at the end of the Pleistocene has been suggested, but human activity has also been implicated.  In more recent years, many of the island populations of giant tortoises have been extirpated by humans, mostly by sailors who collected the tortoises for food.  The introduction of rats, pigs, and dogs by humans to these islands has also had tragic effects on the slow growing turtles.  Adults are generally safe, but the eggs and young are easy prey to the faster, smarter mammals.

A. H. Witte collected the specimen buried at the Dino Pit.  Witte supervised the excavation, which was funded by the Work Projects Administration from 1939 to 1940.  The original specimen was long displayed at the Texas Memorial Museum and is now at the Vertebrate Paleontology Laboratory.


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