RE: crocodylians, amphibians ... (was Sarcosuchus)

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Ken Kinman
>
> Dear All,
>      I strongly disagree with Tom Holtz that this situation is
> analogous to
> calling a titanothere "a rhino", or calling a pterosaur "a dinosaur".  I
> don't know of any prominent scientist who has so grossly
> misclassified such
> reptiles in many decades (and the public should indeed be
> educated on such
> matters).

Bakker, R.T. 1986.  The Dinosaur Heresies.  Don't get more prominent than
that!

(Of course, no scientist has called titanotheres "rhinos", much less
reptiles, lately...).

More to the point, at least some of the scientists talking to the media
(including authors on the paper!!) tried to make the distinction, but to no
avail.

>      Crocodilia/Crocodylia is a completely different matter, as
> this taxon
> has long included a more inclusive "crocodyliform" content, and it is the
> fault of strict cladists for restricting the usage of this term.

You'd have to talk to Brochu or Jim Clark or the like as to the history of
these terms.  At least some, like Mesoeucrocodylia, actually have a long
history in vertebrate paleontology.

> The same
> goes for the even more short-sided redefinition of the term Amphibia
> (especially the most restricted redefinition to the crown group
> lissamphibians).

I would agree I don't like Amphibia restricted to crown-group frog &
salamander relatives.  However, I have no problem with Amphibia being all
taxa closer to _Rana_ than to _Homo_, with Lissamphibia the crown group
amphibians.

>  And try explaining to your fellow non-cladists
> (much less
> the public) the differences between tetrapods and
> stegocephalians, and watch
> their eyes roll or glaze over.

If one were a less-than-engaging speaker, perhaps.  Or if you gave the
distinction a sympathetic hearing.

In fact, I DO explain this distinction (successfully) to the public, and not
just to those over whom I have the "threat" of grades.

One way to point out that _Acanthostega_ and _Ichthyostega_ are not
amphibians or tetrapods in any modern sense is to point out that if you were
a Devonian fisherman and hooked one of these guys on a line, when you hauled
it up you could open its gillflaps to show the nice (pink?) gills, just like
a trout or salmon.  The only real difference between it and animals that
would unquestionably be called fish (like lungfish) that you would be able
to see is that its fins would end in a flared-out mitten with six or seven
or eight prongs.

It's always important to remember the anatomy of these creatures, rather
than simply where one person would fit them on an indented outline chart.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796