[Taxacom] Paraphyletic tagging

Stephen Thorpe stephen_thorpe at yahoo.co.nz
Fri Oct 3 16:46:58 CDT 2014


Yes, but that opens up another can of worms! If the fossil record was complete, who knows what we would find? Possibly only gradual transitions as even major clades evolved, so mammal/non-mammal, for example, would be an entirely arbitrary distinction.

Stephen
--------------------------------------------
On Sat, 4/10/14, Curtis Clark <lists at curtisclark.org> wrote:

 Subject: Re: [Taxacom] Paraphyletic tagging
 To: "taxacom at mailman.nhm.ku.edu" <taxacom at mailman.nhm.ku.edu>
 Received: Saturday, 4 October, 2014, 7:39 AM
 
 To be clear, although
 Stephen's answer works for the extant species, Ken 
 guessed that I meant more globally.
 
 On 2014-10-03 7:22 AM, Kenneth
 Kinman wrote:
 >
 >   
     I would rather phrase it: "Amniotes lacking the
 synapomorphies 
 > of Mammalia and
 Aves".
 
 So we've
 created a taxon based on a lack?
 
 > Hair and feathers would not be the best
 synapomorphies to pick as they 
 > evolved
 too gradually (even baby Tyrannosaurus rex may have had 
 > feathers).
 
 And there are even hairy things in some
 Ornithischia that have been 
 interpreted as
 being homologous with feathers. I'm not saying that 
 thecodonts had feathers, but if a thecodont
 fossil with clear feathers 
 was discovered,
 I wouldn't be astounded.
 
 > For Mammalia, the best synapomorphy so far
 discovered seems to be when 
 > the three
 ear bones decoupled from the mandible.
 
 But unless that happened in a single speciation
 event, there is still 
 the issue of where in
 a gradual shift do we draw the line.
 
 -- 
 Curtis Clark        http://www.csupomona.edu/~jcclark
 Biological Sciences               
    +1 909 869 4140
 Cal Poly
 Pomona, Pomona CA 91768
 
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