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Re: [Re: natatory Geochelone]

Ronald Orenstein <ornstn@home.com> wrote:
> At 11:53 AM 02/07/2000 +0200, Juergen Peters wrote:
> > > In the case of the Galapagos tortise, this makes sense to me. Being
> > > blooded, these animals would not need to eat for a long period of time,
> > > and could therefor endure long ocean voyages.
> >
> >But most probably they did not reach the Galapagos Islands by swimming,
> >as someone mentioned here, but as juveniles on drift-wood etc.
> Actually, according to tortoise experts I have talked to about this, there
is every chance that they DID get there by swimming.  It seems that the
tortoises on the Indian Ocean islands at least (and I suspect the Galapagos is
a similar case) are not cases of insular gigantism but relicts of giant
tortoise populations on the mainland; if juveniles were the colonizers you
might expect some smaller tortoise species to be established there as well. 

Well according to mtDNA sequence done on all the subspecies of _G.nigra_
(formerly _G.elephantopus_) along with a list of South American and African,
mainland tortoises, there closest living relative is the Chaco tortoise
(_G.chilensis_), which happens to be the smallest member of the genus.

So the initial trek to the Galapagos was probably done by a smaller tortoise,
like _G.chilensis_ and then later treks to different parts of the archipelego
probably were done by more elephantine individuals (and indeed mtDNA studies
seem to confirm this).


Abstract available online at: 

Jurassosaurus's Reptipage: A page devoted to the study of the reptilia:


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