UTILITY OF CLADE NAMES

[Tetanurae <Tetanurae@aol.com>]

Jonathon Woolf wrote (quoting me):
<< > This is surprising to you?  Did you think that cladist told people they
had
 > some magical way of deciphering the relationhsips of organisms?
 
 Sure looks that way to me.  Look at the messages I got today claiming
 that cladistics is simply a method of recognizing the existing evolutionary
 relationships between organisms.  >>

Well obviously that is the goal of cladistics: to decipher the evolutionary
relationships between organisms.  This is down by analysing characters.
Anyone who tells you different is either an idiot or a magician.

 <<And maybe we shouldn't keep it.>>

Why should we discard it just because you don't like it?  It was named and
reviewed, so it sticks.  I dislike most names given to everything but I know I
can't go around renaming stuff.

 <<Likewise the other examples you name --
 in ceratopsids, it always struck me as illogical to call something that
 doesn't have either horns or head frill a "ceratopsid."  Ceratopsids are
_horned_
 dinosaurs -- and for the sake of simplicity, anything descended from a horned
 dinosaur, like _Pachyrhinosaurus_.  Even protoceratopsids could be reasonably
called
 horned dinosaurs, since the male _Protoceratops_ has an incipient horn on its
 nose.  But _Psittacosaurus_ isn't a horned dinosaur and shouldn't be placed
in
 Ceratopsia.>>

Why?  It has huge jugal horns that come off of a ridge on the postorbital and
the jugal, a rostral bone and squamosal shelf over the occiput.  That screams
Ceratopian to me.  Additionally, how horny does a horn have to be to be a
horn?
 
 <<Why was Ornithopoda expanded to include dinosaurs without birdlike
 feet?  And who did it?  Some evangelical cladist on a crusade?>>

The truth of the matter is that ornithopod feet don't resemble the feet of
birds very much, and it was not some evangelical cladist, it was a 19th
century paleontologist who saw the utility of expanding group names and the
uselessness of proliferating new names.
  
 <<If that's how it's defined, then it should be named in a way that
 reflects the definition.>>

It does reflect the way Arctometatarsalia was defined, an arctometatarsus is
present in Ornithomimus and all known members of that clade, and absent in all
modern birds.

 <<It's not me that's confusing the two -- it's the guy who named the
 group, because he gave it a name that implies any member of the taxon
 will have a certain diagnostic feature.>>

I will let "the guy who named the group" field this

 <<Names have meaning.  Names have power. Anyone who sees the _name_
Arctometatarsalia is going to automatically conclude that the name relates to
a feature common to all members of the group,>>

Not necisarily.  They will see it as a stem based clade thatt includes
Ornithomimus and all animals that share a more recent common ancestor with
Ornithomimus than with birds and that some members of that group will have
been characterised by possesing an arctometatarsus.  Hopefully these people
will have had the foresight to read Holtz 1994, 1995 and 1996 so they would
understand that.

 <<Diapsida (two-holes),>>

Lizards are diapsids, yet they lost the lower portion of one of their temporal
openings

 <<Echinodermata (spiny skin),>>

Sea cucumbers are echinoderms and they are some of the most unspiny (and
generally gross feeling) animals around.  By your logic you should also place
certain sponges and rose bushes into Echinodermata

 <<The definition is included in the name.>>

Not really, as with Echinodermata, spiny skin is really a poor character to
choose if that's what you really think the name is for.  The name has nothing
to do with them being deuturostomic triploblasts and ignores the fact that
they are bilateral as larvae, yet take on a usually pentaradial symetry as
adults.

A name is just a name after all, it doesn't have anything to do with the
definition, diagnosis or membership.  Holtz could have named the clade Fred
for all I care, it would still be the same thing and contain the same
information as Arctometatarsalia.

Peter Buchholz
Tetanurae@aol.com

"While you're at it, go ahead and leave that moldy futon bed you left outside
in the yard for four years, because that will be a JOY for those who move in
after you.  You know, I just might need a virtually immovable, soggy and moldy
futon bed sometime!  So why not leave that behind"