Re: Say this slowly: theropoda is paraphylitic, theropoda is paraphlyitic.....

[Stanley Friesen <sarima@friesen.net>]

At 08:55 AM 6/26/00 -0400, ELurio@aol.com wrote:

> Let's see, I get told that the term  paraphyletic is actually the term
> polyphyletic.
> right then you tell me that it isn't. Hmmmmm......
The two terms have different meanings.  A paraphyletic group is one that 
includes the most recent common ancestor of all of its members and of each 
pair of members, but excludes one or more monophyletic groups of its 
descendents.  A polyphyletic group is one that either does not include the 
common ancestor of all members, or does not include the common ancestor of 
some pair of members.

Thus a given the current best cladograms, _Theropoda_ *without* birds is 
paraphyletic.  A Theropoda consisting of several disjoint clades each 
derived from a non-theropod ancestor would be polyphyletic.

--------------
May the peace of God be with you.         sarima@ix.netcom.com