> 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.
>
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.
+++++++++++++++++++++++++++++++++++++++++++++++++++++
I get how these taxa can be an issue, but they are also the exceptions to the rule. There will always be a few taxa that are going to be a problem. Same as with the dinosaurs most closest to the base of Aves. We got lucky with dinosaurs, humans, horses and a handful of other taxa, in that the fossil record is complete enough to show an almost gradual evolution from one group to the next, resulting in the transitional groups being the hardest to categorize because they are so close to our imaginary dividing line. A similar case can be made for when a collection of cells becomes tissue and when tissues become organs, or even when non-life becomes life. At a fine enough scale all these things bleed together. However, the situations we are talking about are rare and the problem taxa represent edge cases. Referring to any dinosaur outside of Pennaraptora as dinosaurs in the paraphyletic sense, doesn't hurt the meaning at all or cause any confusion. The addition of a monophyletic alternate name also allows those who prefer a strict monophyly to happily have it too. I suspect that this is the main reason why there was never any real arguments about this in herpetology, regarding snake taxonomy. It has long been established that snakes evolved from lizards, but only a few herpetologists ever refer to snakes as lizards, instead opting for the monophyletic Squamata.
All that said, whether Archaeopteryx is the "first" bird, a crown bird or a strange dinobird has been argued back and forth for decades even after the advent of a monophyletic Dinosauria. Insisting on monophyly hasn't really done anything to make that argument any easier.
Jason