MattI think it's worth pointing out, in a discussion about nomena dubia, that the ICZN says nomena dubia *should not be allowed to exist*. It is pretty clear that if the type specimen of a species is found to be indeterminate, by taxonomic obsolescence or otherwise, a neotype needs to be designated in order to preserve stability. Deinotontidae was in use for nearly 100 years and Deinodon treated as valid (often as a synonym of Gorgosaurus) during much of that time. IIRC, in the 1970s, it was Dale Russel's work on deinodontids/tyrannosaurids that concluded Deinodon was a nomen dubium, and therefore taxonomy based on it was also invalid. This was pre-PN and a blatant disregard for the ICZN. Russel should have chosen a neotype from available comparable specimens, and had a great opportunity to do so since he simultaneously spun off a new taxon from the Deinodon/Gorgosaurus complex: Daspletosaurus. If Russell had followed the rules instead of taking the opportunity to coin a new name, we wouldn't be in the current situation of having to selectively ignore the rules we've got in this instance. Neotypes are rare in paleontology and we've got hundreds of nomena dubia to show for it.I guess my point is that one generation's concept of stability and commonly-used names are often the result of past instability and coining of new names for old taxa by a very few but very prominent researchers in the past. We can choose to either have stability in our nomenclature, or "go with the flow" of whatever name is trendy today and accept generational turnover in nomenclature, but anybody who chooses the latter has abandoned their right to ever criticize anyone for not using the "correct" nomenclature, because "correct" becomes whatever the personal preference of the top celebrity researchers happens to be that decade.On Fri, Apr 15, 2016 at 4:08 AM, Mickey Mortimer <mickey_mortimer111@msn.com> wrote:Tim Williams wrote-
> Frankly, yes. Subjective it may be, but arbitrary it is not. The
> 'subjective' determination is based on scientific expertise and
> experience. In my view, that trumps the arbitrary rules of the ICZN,
> which only avers that the family that was named first gets priority.
>
> When defining a clade with the eponymous genus as the specifier, it's
> best to use a genus that is actually valid. I know 'validity' is
> sometimes in the eye of the beholder. But for _Deinodon_, I don't
> know of anyone who thinks it's valid. So I can't see any reason why
> Deinodontoidea should supplant Tyrannosauroidea.
>
> I understand your Spinosauroidea/Torvosauroidea/Megalosauroidea
> example... yes, Megalosauroidea eventually won out. After all, it has
> priority. Recent studies support _Megalosaurus_ as a valid genus, so
> I've got no problem with clade Megalosauroidea.
But Megalosaurus was often viewed as indeterminate prior to Benson et al.'s (2008) restudy (e.g. Rauhut, 2000; Allain and Chure, 2002) back when only the lectotype dentary was referred because it was thought multiple large theropods were preserved at Stonesfield Slate (Morphotypes A and B, etc.). So if we were having this discussion then, you'd say no one should resurrect Megalosauroidea because we already have a good definition for Spinosauroidea. But now you're fine with it. Don't you note the inconsistency? If we find a supposed nomen dubium is valid in the future, then do we have to change the clade name? Or are we in a special time where whatever the consensus is for validity for every taxon now is seen as binding? Or do you not even care, and figure we'll just go with the flow of whatever feels right for each situation?
And choosing diagnosability is just as arbitrary as anything else. WHY should specifiers of clades be diagnostic? What's the downside if they're not? And before you say it again, no you don't have to include a nomen dubium in a quantified phylogenetic analysis in order to determine its relationships. You look where the taxa are that it can't be distinguished from, and that range of the cladogram is where it goes.
> Of course, we could just have names like Megalosauria, Tyrannosauria,
> Oviraptoriformes, Caenagnathia, Caenagnathiformes, etc (and avoid the
> suffix -oidea), which would bypass ICZN altogether.
And destroy historical continuity, plus disrespect the people who named each family-level clade. Though of those, only Caenagnathia doesn't already exist.
> Yep, I'm aware there's no consensus regarding the 'standard'
> definition of many clades. Aves is a famous/infamous example. I
> agree that PhyloCode should solve these sorts of problems. But having
> coordinated family-level taxa governed by ICZN rules just adds an
> additional (and unnecessary) layer of complication.
It doesn't complicate, it organizes. It's another layer of rules, but if you always follow all the rules you'll get a definite answer. And if you don't like that answer, you can petition. I don't get why you prefer a system where everyone just sorta goes with what they want, and if a consensus forms great, but if one doesn't no one's actually wrong. Is is selfishness of wanting to use the names you like, laziness of not wanting to work through the rules, an anti-authority grudge of thinking we deserve unlimited power over the system?
Mickey Mortimer
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