[Taxacom] dinosaurs and wolves

Ken Kinman kinman at hotmail.com
Wed Oct 3 19:03:22 CDT 2012


Hi Wolfgang,
       I can't help but wonder what they mean by "re-evolution" of legs.  If they mean that there was still a tiny proximal vestige left and then distal elements re-evolved from it, that wouldn't seem so difficult.  However, if they mean there was no vestige of the hind legs left at all and then re-evolved the entire leg, that seems very unlikely----so much so, that I would lean toward multiple losses as more parsimonious.  Loss of limbs seems relatively easy in both lizards and snakes, compared with other reptiles, birds, and mammals (which need those front flippers to swim, even if the hind legs have disappeared).    
                    -------------Ken 

Date: Wed, 3 Oct 2012 19:06:50 +0100
From: w.wuster at bangor.ac.uk
To: kinman at hotmail.com
CC: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] dinosaurs and wolves


  
    
  
  
    On 03/10/2012 18:17, Ken Kinman wrote:

      

      Hi,

      

      Pachyrhachis and relatives tend to float a bit, grouping variously
      as sister to the Macrostomata, within them, or slightly further
      out near the base of the Alethinophidia. In all cases, however,
      the authors note that the hypothesis of a single re-evolution of
      legs is more parsimonious than the alternative of multiple losses.
      Obviously, the most parsimonious solution is not *necessarily* the
      correct one, but at the end of the day we will have to await new
      fossil discoveries for more conclusive evidence.

      

      The paper itself ("Assembling the Squamate Tree of Life:
      Perspectives from the Phenotype and the Fossil Record") is well
      worth reading, containing a host of new morphological characters,
      and also discussing the extreme lack of congruence between
      molecular and morphological data, particularly in relation to the
      position of the Iguania in squamate phylogenies.

      

      Wolfgang

      

      

    
    
      
        
        
          Hi Wolfgang,   
          

          
                I haven't seen the newest phylogeny (by Gauthier et
            al., 2012), but I assume that it further solidifies the
            general consensus that Pachyrhachis and relatives are
            macrostomatan snakes (not sister group to all snakes).
             However, even that would not necessarily mean that they
            re-evolved legs.  Isn't there also a general consensus that
            it only indicates that snakes lost their legs numerous times
            (in different lineages)?     
          

          
                       -------------Ken             
          

---------------------------------------------------------------------------------------------------------

          > Date: Wed, 3 Oct 2012 07:47:21 +0100

            > From: w.wuster at bangor.ac.uk

            > To: taxacom at mailman.nhm.ku.edu

            > Subject: Re: [Taxacom] dinosaurs and wolves

            > 

            > On 03/10/2012 04:58, Ken Kinman wrote:

            > > Stephen,

            > > I didn't say anything about reversals requiring
            reactivation of genes. I certainly know of no snakes or
            marine mammals reactivating leg genes and the reinvention of
            legs.

            > 

            > Actually, there is reasonable evidence that
            simoliophiid snakes 

            > (Pachyrhachis, Haasiophis) may have re-evolved hind
            limbs, based on 

            > their possession of these appendages and their nesting
            deep in the 

            > ophidian phylogeny. See Gauthier et al., Bulletin of
            the Peabody Museum 

            > of Natural History 53(1), April 2012.

            > 

            > Wolfgang

            > 

            > 

            > -- 

            > Dr. Wolfgang Wüster - Lecturer

            > School of Biological Sciences Bangor University

            > Environment Centre Wales

            > Bangor LL57 2UW Wales, UK

            > Tel: +44 1248 382301 Fax: +44 1248 382569

            > E-mail: w.wuster at bangor.ac.uk

            > http://pages.bangor.ac.uk/~bss166/

            > 

            > 

            > 

            > 

          
        
      
    
    

    

    -- 
Dr. Wolfgang Wüster  -  Lecturer
School of Biological Sciences    Bangor University
Environment Centre Wales
Bangor LL57  2UW                 Wales, UK                       
Tel: +44 1248 382301  Fax: +44 1248 382569
E-mail: w.wuster at bangor.ac.uk  
http://pages.bangor.ac.uk/~bss166/





  



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