Re: Dino Birds (was Re: Dinosaur = extinct animal)

[Dinogeorge@aol.com]

In a message dated 7/12/99 2:20:50 PM EST, cbrochu@fmppr.fmnh.org writes:

<< In set theory, yes.  Biologically, no.  "Real" biological groups are
 delimited by natural, external bounds that exist beyond human
 subjectivity.  Common ancestry forms such a basis - provided we agree
 that evolution has occurred, divergence events form the lower bounds of
 groups.  >>

This is merely a philosophical difference about the definition of "real." 
Suppose we have a clade A and an included clade B. Use whatever criteria you 
like to decide whether a species belongs to A or more specifically to B. The 
same criteria will also tell you at once whether the species belongs to taxon 
A-B. A-B is just as real as either A or B.