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Re: Croc classification (was Re: Sarcosuchus and Dumbing things down)
I'm going to prune sections of this to save bandwidth.
Contrary to the assertions of several cladists, Owen did not use the term
'Crocodylia' (with a 'y' instead of an 'i') when he emended Gmelin's
Crocodili in 1842 to additionally encompass fossil taxa.
I don't recall cladists (including myself) referring to Owen for taxonomic
Well maybe you should.
Why? We're working in an evolutionary framework, Owen worked on a
typlogical framework. Different frameworks.
Up until 1973,
Crocodilia was broadly equivalent to what most cladists now call
Crocodylomorpha. About the only point of contention prior to 1973 (and
indeed for about a decade after) was whether Sphenosuchia should be placed
in Crocodilia or Thecodontia.
Crocodylomorpha = "sphenosuchians" + crocodyliforms. I think you mean "in
the older usage, Crocodilia meant "Crocodyliformes."
No. Some poeple considered spenosuchians members of Crocodilia (hence the
comparison to Crocodylomorpha), whereas others excluded them, placing them
in Thecodontia instead, hence making Crocodilia broadly equivalent to
Isn't that what I just said? Leave out the "sphenosuchians," and you
had relatively broad agreement over content - that's Crocodyliformes.
Add the "sphenosuchians" and you get Crocodylomorpha.
> I think some posters to this list have the misimpretion that "Crocodilia"
had a stable meaning before the crown-group definition was published in
1988 - and Ken, you'd be VERY surprised at who the senior author of that
paper was. If it did, there'd not have been a need for a revised
definition. Most people agreed that things like dyrosaurids and
notosuchians should be "crocodilians," but what about Gracilisuchus? or
Terrestrisuchus? Were these "crocodilians" or "thecodonts?" The lower
bounds of "Crocodilia" in the former usage were absolutely unclear and
Is it any different now? Just compare the works of Clark, Wu, Sues,
Brinkman, Parrish, Sereno and Wild.
Yes. Details of phylogeny among, say, the "sphenosuchians" are in
dispute, but the range of the tree between Crocodylomorpha and
Crocodyliformes is stable. That's why the stability sought for in
phylogenetic nomenclature is meaning, not content.
It's not what I propose; I'm just going along with Owen and Huxley.
Taxonomic stability is an unachievable Holy Grail. In any case, it makes
systematics more enjoyable.
See a previous post of mine - there are different kinds of
stability. I think you're thinking about stability of content, and
we're more interested in stability of meaning.
In the context of the Linnean system, perhaps. But we no longer use the
Linnean system (or shouldn't), so whether one spelling or the other in the
Linnean system has priority is irrelevant to the crown-usage currently in
Whose 'we'? Not me. I'll use which ever system I think is most
appropriate. And for purely taxonomic purposes, the Linnean system wins
hands down. Phylogeny is something else.
If the Linnean system were so great, why are we eliminating it? Just
to be a bunch of annoying persons?
Christopher A. Brochu
Department of Geoscience
University of Iowa
Iowa City, IA 52242