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Re: Reptiles

On Sat, 19 Dec 1998, Lee J. McLean wrote:

> As far as I'm concerned, the term 'reptile' carries far too much
> historical baggage to be of any use as a formal taxonomic term, as the
> current debate here shows.

I could say the same for "dinosaur". The public at large thinks it
includes pterosaurs, _Dimetrodon_, plesiosaurs, ichthyosaurs, even
saber-tooth cats and mammoths. People have asked me questions on my site
about prehistoric sharks, f'r cryin' out loud!

> One of the worst things about cladists is the way they redefine already
> well-defined terms - instead they should introduce new ones (or stick
> with the established formal names - what was wrong with the far less
> confusing "Sauropsida"?). 

Sauropsida *is* a clade -- it's different from Reptilia, though. Reptilia
is the most recent common ancestor of turtles, lepidosaurs, and
crocodiles, plus all of its descendants. Sauropsida is all animals sharing
more recent ancestry with living reptiles than with living mammals. Hence
Sauropsida is slightly more inclusive than Reptilia -- by most
phylogenies, it includes mesosaurs as well as reptiles.

> The term 'reptile' should be used informally only, referring to
> cold-blooded, scaly tetrapods (as per its original definition, which
> would exclude dinosaurs IMHO).

As pointed out, the original definition included sharks and sturgeons! 
Taxonomy has been highly volatile since the days of Linnaeus, and this is
something cladistics can remedy. By sticking to the rules of priority, we
can eliminate the instability of taxon definitions. Unfortunately,
sometimes a name that has priority is not a great name: Pseudosuchia,
Ornithosuchia, Reptilia, Paraves, Ornithischia, etc. It happens with
genera and species, too: _Sarcolestes_, _Proceratosaurus_, _Ultrasaurus_,
etc. But just saying "I don't like it, so I won't use it" is completely
antithetical to the spirit of formal taxonomy. Formal taxonomy is supposed
to create *universal terms* for scientific discussion. If people
individually decide that they don't like a particular term, this destroys
the idea of a universal language, and hinders communication.

> Next they'll try to formally redefine the term 'fish' to include all
> gnathostomes (and once again abandon an already perfectly good and
> well-established formal name)! 

Gnathostomata has been cladistically defined already, but "Pisces" has
not (and probably will never be). No worries there.

--T. Mike Keesey                                   <tkeese1@gl.umbc.edu>
THE DINOSAURICON                http://www.gl.umbc.edu/~tkeese1/dinosaur