CLADISTICS AND CLADE NAMES

[Tetanurae <Tetanurae@aol.com>]

Jonathon Woolf wrote:
 <<Ahhh, now that's not the same thing I was hearing earlier.  _That_
description
 makes sense.  But claiming that a cladogram simply recognizes the existing
 evolutionary relationships, as if the cladogram is unquestionable revealed
truth
 -- _that_ is magic.>>

Of course it is magic because no one has made that claim.  A published
cladogram is one of many possible cladograms produced in an analysis, usually
the one with the most parsimonious distribution of charatcers.  Cladograms are
labeled as being "a phylogenetic hypotheses" based on the most parsimonious
distribution of characters etc etc etc.
 
 <<_Tyrannosaurus_ has brow horns, and _Ceratosaurus_ has a nose horn.  Does
that
 make them ceratopsians?  The rostral bone alone is enough to mark
_Psittacosaurus_
 as *related* to ceratopsians, maybe even close to a ceratopsian ancestor, but
it
 doesn't make _Psittacosaurus_ a ceratopsian any more than a hadrosaur-like
bill
 makes _Ouranosaurus_ a hadrosaur.>>

Psittacosaurus is a Ceratopian  because Ceratopia is a stem-based clade
period.  Ouranosaurus is NOT an hadrosaurid because Hadrosauridae is a node
based clade period.

 <<<shaking head in disbelief>  Before this exchange, I would have sworn that
nobody
 could be this deliberately dense, except maybe creationists and animal rights
 activists.>>

Let's keep the ad hominem off the list.

<<THE NAME ALONE DOES NOT COMMUNICATE THAT DEFINITION.  THE NAME ALONE
INDICATES THAT THE MEMBERS OF THE GROUP ALL HAVE THE ARCTOMETATARSUS AS A
SYNAPOMORPHY.>>

No it doesn't.  It implies that some members might have an arctometatarsus.  A
perfect example of this is Cerapoda which translates (very badly I might add)
to "Horned Feet."  NO CERAPODAN DINOSAURS HAD HORNS ON THEIR FEET.  So what!?
The name sticks period.  There are a lot of nonsense names that I have no
intention nor want of changing.

It is clear that JSW does not understand phylogenetic taxonomy, the meanings
of node and stem based clades and the difference between diagnosis and
definition.  If you wish to become better informed, I would be happy to
photocopy papers and send them in the mail to you.  However if you simply wish
to argue without having a clue about what you're talking about, I would
suggest you rethink that.

Peter Buchholz
Tetanurae@aol.com