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Re: Digits



I went to the library today and photo copied me a copy of Shubin, 
Wake, and Crawford's 1995 paper on Taricha.

It's an interesting article, but I have a problem with this being a 
caseof  "re-evolving" bones. Modern amphibians are a very plastic (I 
don't know if this is the right word) group of animals. As this paper 
shows, the sample size (453 individuals) shows a 18.9 % tarsal 
variations, and 9.3% carpal variations. What has happened in these 
individuals have 'grown' several new tarsals or carpals. The authors 
refer this to a primitive state, like that found in Trematops 
(Trematops has been sunk into the genus Archeloma, or has that 
changed?). Trematops didn't have anything to do with modern amphibians.

There are some modern amphibians that have grown more toes than normal. 

But, I have seen dozens of articles on supernumerical toes, and limbs 
(I had run across the articles doing research for Darren Tanke's 
Paleopathology bibliography). Frogs with more than 4 limbs, and up to 
as many as 8 legs. Is this a case of re-evolving lost limbs? No. All 
this is is a case of a chemical imbalance while the animal was growing, 
this imbalance changed what ever it is that determines how many toes, 
legs, heads, and that's all. 

There are papers that artificially changed the chemical balance in the 
egg while the amphibian was developing, and that change caused more 
toes, legs, etc.

I would believe that re-evolving toes, what ever, took place IF the 
later offspring showed these changes, but this is not the case.

Tracy