Re: [dinosaur] Party like it's 1758!

[Tim Williams <tijawi@gmail.com>]

Jura <pristichampsus@yahoo.com> wrote:

> And look at the crapstorm that has created. Even now, the use of a 
> monophyletic Dinosauria is still challenged or begrudgingly accepted. Just 
> look at how often a paper or book will have a variant of
> this phrase in the introduction: "Non-avian dinosaurs (which we will refer to 
> as just dinosaurs for the rest of the text)". Strict phylogenetic terms are a 
> problem when referring to concept-based names.
> The glut of "non-avian dinosaur" in the literature also makes it pretty clear 
> that the old, paraphyletic definition still has merit.

Yes I can see how a paraphyletic group could have merit, purely for
convenience.  However, I still think we're heading down the same
typological rabbit-hole that phylogenetic nomenclature is trying to
correct.

> Artiodactyla is another concept-based name. It's referred to when dealing 
> with all the various, terrestrial even-toed ungulates, but whales are very, 
> very different from most artiodactyls. Using the
> monophyletic definition of Artiodactyla in most research studies, would 
> either require an ugly modifier like "non-cetacean artiodactyl", or some kind 
> of qualifying statement at the beginning of the text.
> Making Cetartiodactyla the monophyletic name frees up the concept-based 
> Artiodactyla, allowing it to continue to function as a paraphyletic group. No 
> information is lost and it doesn't deny the
> inclusion of whales as a branch of this mammalian group.

Non-cetacean artiodactyl (like non-cetacean cetartiodactyl) is
certainly ugly; but there are situations when it is entirely accurate.
It also spares us having to argue over which taxa are (or are not)
included in the concept-based definition of Artiodactyla.  This
becomes more fraught the closer you get to the base of Cetacea,
because of the issue of transitional taxa.  For example, is _Indohyus_
an artiodactyl or a cetacean?  What about pakicetids (which, after
all, were digitigrade and hoofed)?  With phylogenetic nomenclature,
with Cetacea just one clade among many clades inside clade
Cetartiodactyla, this isn't an issue.  On the other hand, with a
concept-based Artiodactyla and a concept-based Cetacea, transitional
taxa (like _Indohyus_ and pakicetids) get caught up in a 'tug-of-war'
over which concept they best fit.

> If anything, it retains the highest degree of fidelity in the literature by 
> not diluting the group definition. I can read a paper from the 50s, 70s, or
> 10s and know exactly what the researchers are referring to when they say 
> artiodactyl vs. cetartiodactyl.

I don't see this as a problem.  We can acknowledge the typological
concepts that previously governed taxonomy - but I don't think we
should be beholden to them.

> Honestly, it's disappointing that the same wasn't done for dinosaurs. If we 
> went with a monophyletic "Avedinosauria" and a paraphyletic "Dinosauria" I 
> suspect there would be much less confusion in
> the literature when it comes to using the name.

Again, I can see advantages of this approach, purely for simplicity.
But I still disagree with this approach.  Having a monophyletic
"Avedinosauria" and a paraphyletic "Dinosauria" is still far too
typological for my liking.  I can see a whole new crapstorm brewing
over where a paraphyletic "Dinosauria" ends.  If "Dinosauria" stops at
the crown bird clade (Aves), then _Archaeopteryx_, _Ichthyornis_, and
Enantiornithes would all be dinosaurs, distinct from crown birds.  But
if Aves is more inclusive, and includes _Archaeopteryx_ and these
other stem taxa, then _Deinonychus_, _Microraptor_ and _Anchiornis_
would be considered dinosaurs, but not _Archaeopteryx_ etc.  I'm
uneasy about these delineations.  The intention is good, but the
outcome is still typological.