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RE: Ah ha! That's where therizinosaurs came from



  That would be an interesting idea to test. Can we find a group of taxa which 
have redeveloped dentition from a loss? Certainly, therizinosaurs can escape 
this issue since none of them have lost dentition save for the premaxilla; 
instead, we'd attempt to see if new dental positions arise from an ancestral 
condition in which is is lacking. This does not appear to occur in mammals, 
although it may occur in less provincialized dental organizations, as in 
lacertilians. Reversal and rejection of Dollo's Law is a variation of this 
concept, and has been tested on the specific with regards to tree frogs (e.g., 
Weins, 2011), but this is in relation to whole series tooth loss and reversal, 
rather than series expansion into otherwise edentulous regions of the jaw. 
Tooth duplication, where genetic abnormalities cause teeth to appear in 
addition to the normal number and which are morphologically identical to 
adjacent teeth, has occurred in mammals, while other studies regard the 
variable appearance of canines in deer. This subject has been assessed in 
relation to humans, where is may end up with anomalies such as a tooth being 
rotated, having additional roots, or appearing as duplicated, and are 
associated with development disorders.

Weins, J. J. 2011. Re-evolution of lost mandibular teeth in frogs after more 
than 200 million years, and re-evaluating Dollo's Law. _Evolution_ 
65(5):1283-1296.

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)


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> Date: Tue, 9 Aug 2011 01:12:39 -0400
> From: archosauromorph2@hotmail.com
> To: dinosaur@usc.edu
> Subject: RE: Ah ha! That's where therizinosaurs came from
>
>
> > Date: Mon, 8 Aug 2011 23:22:17 -0400
> > From: GSP1954@aol.com
> > To: dinosaur@usc.edu
> > Subject: Ah ha! That's where therizinosaurs came from
> >
> > What has become most vexing is those pesky therizinosaurs. Some have those
> > very long tails. So what basal flying theropods were herbivores with long
> > tails? Well duh, jeholornithids. Not that jeholornirds specifically are
> > prototherizinosaurs, they lack sufficient teeth for one thing.
>
> Or maybe therizinosaurs were neotoothy. ;)