Aldabra and Galapagos Genera

[Kadaan]

I just noticed that even though Aldabra and Galapagos tortoises seem very similar, they're actually in two different genera (dipsochelys and geochelone.)

What differences made Aldabras and other Seychelle giant tortoises into their own genus? I haven't found any detailed articles, but it sounds like they used to be classifed as geochelone and were re-classified sometime in the 80's.

 

[egyptiandan]

Actually Galapagos tortoises are in the genus Chelonoidis. The genus Geochelone had always had subgenus, which were Geochelone, Astrochelys, Albabrachelys, Cylindraspis, Manouria, Indotestudo and Chelonoidis. All they did was elevate all the subgenus to the genus level.
You can use either Aldabrachelys (Loveridge and Williams 1957) or Dipsochelys (Bour 1982) for Aldabra tortoises. Chelonoidis has been around since 1835 (Fitzinger 1835)

Danny

 

[Yvonne G]

And after looking at the pictures in the link Gummybear provided for us yesterday in his "tortoises in trouble" thread, its fairly obvious that they are closely related. The picture of the saddleback Seychelle tortoise was SO like the saddleback Galop.

Yvonne

 

[egyptiandan]

Actually they aren't very closely related Yvonne. The "saddlebacks" of the Seychelles and the Galapagos are what is considered convergent evolution. They both evolved seperately, but in similiar habitats. That means their bodies took on the same design to survive in the same arid habitat. http://en.wikipedia.org/wiki/Convergent_evolution

Danny

 

[Madkins007]

Unfair! When I get all taxonomic, people abuse me.

It is dangerous to assume two things are closely related just because they look a lot alike. These two groups have been apart for at least as long as South America split off Africa. The most obvious difference is the nuchal scute, just above the neck. South American tortoises do not have these, but Aldabrans do.

The Aldabrans used to be related to a large group of giant tortoises throughout the Seychelles Islands area, but most have been eliminated until only the Aldabran, the Seychelle Giant, and the Arnold's Giant Tortoises remain, and these last two are only in zoos and protected areas.