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Re: Re: Removing segnosaurs from ...



>In a message dated 95-08-29 11:01:41 EDT, Thomas_R_HOLTZ@umail.umd.edu (th81)
>writes:
>
>>If you wish to be a strict Dollist (Dolloist?  sp.), sure.  If not, you can
>>recognize that homeobox genes show that there really aren't any significant
>>morphological characters that can't be reversed.
>>
>>
>
>Yeah--With a great deal of biotech effort, we can get birds to regrow the
>teeth they lost. But how often does this happen in the wild? And how would we
>identify such a case from the fossil record?
>

Reversals do occur sometimes in nature: there are apparent reversals in
sacral numbers in the evolution of horses (granted, a simpler situation than
the metatarsals.)

And, as with any example of homoplasy, reversals can ONLY be identified
posteriori after some form of phylogeny has been constructed.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD  20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661
Phone:301-405-4084