[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: tiny-armed theropods



And there we go with what Tim's argument also boils down to.  You *think* that 
nomina dubia and other taxa of questionable identity shouldn't be used for 
taxonomic purposes.  Which is an opinion, but not backed by the ICZN.  And the 
Phylocode isn't enforcable yet, and doesn't have anything about nomina dubia in 
it either.  So while you can have your opinion, it's not something that the 
community has any need to follow, and doesn't concern me until you or Tim show 
that basing Troodontidae on ANSP 9259 (as in ANSP 9259 <- Dromaeosaurus, 
Passer) has a realistic possibility of resulting in a clade that does not 
include troodontids as now conceived.  That's the only thing to be worried 
about when choosing a specifier for a clade (well, that and eponymity).  

"the problem is that if it's just a tooth, we don't know what else that group 
entails"

That's just not true.  Just being fragmentary doesn't mean we have no idea what 
group it belonged to.  It's 'definitely' (in the sense of what the evidence 
currently indicates, as is the case for every phylogenetic assignment) a 
vertebrate, a reptile, a theropod, a coelurosaur, a paravian, a troodontid, 
etc..  If there was some other clade it might belong to besides Troodontidae as 
currently defined, THEN I would agree with you.

Mickey Mortimer

----------------------------------------
> From: qi_leong@hotmail.com
> To: mickey_mortimer111@msn.com; dinosaur@usc.edu
> Subject: RE: tiny-armed theropods
> Date: Sun, 16 Oct 2011 02:22:43 -0600
>
>
>   I think that if we don't know what _precisely_ *Troodon formosus* is, it 
> shouldn't serve as a valuable-basis for further taxonomy. In many ways, taxa 
> of uncertain position, qualification, or material should not be the basis of 
> further taxonomy, even if we were super-duper sure it was awesome and unique. 
> It should not be coordinated to ranks, or valuable as the anchors for clade 
> definitions; and if we are using *Troodontidae*, it must include *Troodon 
> formosus* -- the problem is that if it's just a tooth, we don't know what 
> else that group entails. Best to leave it out of definitions without surety. 
> If it falls by the wayside, so be it. Supporting it for historical reasons, 
> which is otherwise the _only_ reason it's still used, falls afoul of all the 
> other historical taxa we've dumped and it becomes a special case of 
> ridiculousness.
>
>   Oh, and if were are including it, to pretend that the tooth is the 
> qualifying element of the phylogenetic analysis, then let all other things be 
> equal: Test ONLY specimens. Otherwise, the analytical analysis is testing a 
> complex of specimens, or a conflated taxon, against a single specimen, and 
> this means what you are actually testing are not equals. Placing a specimen 
> into such analysis without qualifying the preservation or variation therein 
> means you're chasing after shadows, not doing _science_.
>
> Cheers,
>
> Jaime A. Headden
> The Bite Stuff (site v2)
> http://qilong.wordpress.com/
>
> "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
>
>
> "Ever since man first left his cave and met a stranger with a
> different language and a new way of looking at things, the human race
> has had a dream: to kill him, so we don't have to learn his language or
> his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
> Backs)
>
>
> ----------------------------------------
> > Date: Sun, 16 Oct 2011 00:27:45 -0700
> > From: mickey_mortimer111@msn.com
> > To: dinosaur@usc.edu
> > Subject: RE: tiny-armed theropods
> >
> >
> > Look Jaime, your long replies have many interesting aspects, but are 
> > ultimately not useful for arguing against what I'm advocating here. I 
> > actually agree that what we currently think of as Troodon formosus is 
> > probably several species, given the variation in frontal and dental 
> > morphology. Some may be more closely related to Zanabazar, Talos or 
> > Linhevenator than others, who knows. Maybe the holotype tooth is maxillary, 
> > or is undiagnostic. It all doesn't matter for Troodontidae being a fine 
> > name for the clade it currently defines. Unless you actually think ANSP 
> > 9259 is a dromaeosaurid, bird or other reptile, and have evidence 
> > supporting that which is better than the evidence we have now showing it's 
> > related to Zanabazar and such, it doesn't matter. You may indeed get a huge 
> > polytomy if you analyze ANSP 9259 with the types of Stenonychosaurus, 
> > Paronychodon, Polyodontosaurus and such, but as long as ANSP 9259 is in 
> > "Troodontidae" as we now conceive it once you delete enough taxa (a 
> > posteriori of course) to recover the clade, then it's okay.
> >
> > And in reply to Tim Williams' post of
> >
> > "My example of _Deinodon_ is to show what *could* happen to _Troodon_ (it 
> > hasn't yet). _Deinodon_ was originally named from teeth that were once 
> > considered distinctive. However, later discoveries of tyrannosaurid 
> > specimens showed that the tooth morphology of _Deinodon_ was actually 
> > common to several tyrannosaurid genera. So the _Deinodon_ teeth were 
> > therefore no longer distinctive (= diagnostic) at the genus or species 
> > level. Result: _Deinodon_ is a nomen dubium."
> >
> > This is actually an example of the kind of taxonomy I decry. Contrary to 
> > popular belief, Deinodon was never shown to be a nomen dubium. Rather, 
> > Russell (1970) merely asserted "... it is not possible to distinguish them 
> > [libratus and torosus] from each other or from Deinodon on the morphology 
> > of the premaxillary dentition...". No explicit comparison, no illustrations 
> > or tables. And everyone since has just accepted it as true, despite the 
> > fact Russell also used one genus for libratus and sarcophagus, thought 
> > lancensis was an adult and "quite similar" to albertosaurines, etc.. People 
> > don't want to deal with the messy implications of a valid Deinodon and 
> > don't want to bother actually comparing Gorgosaurus and Daspletosaurus 
> > teeth in depth, when we already have the neat consensus taxonomy. But as 
> > good of a paper as Russell's was for 1970, that was 41 years ago. I don't 
> > exactly trust an unreferenced opinion like that.
> >
> > Mickey Mortimer
> >
> >
> > ----------------------------------------
> > > From: qi_leong@hotmail.com
> > > To: mickey_mortimer111@msn.com; dinosaur@usc.edu
> > > Subject: RE: tiny-armed theropods
> > > Date: Sat, 15 Oct 2011 19:05:47 -0600
> > >
> > >
> > > Mickey,
> > >
> > > Taking the discussion in hand, several issues arise:
> > >
> > > 1. There is no objective reason to prove it _is_ a premaxillary tooth, 
> > > contra your assertion. (It's curvature and morphology, sans mesial 
> > > serrations, actually imply it is a maxillary tooth, but if it _were_ a 
> > > premaxillary then even the size discrepancy among maxillary/premaxillary 
> > > teeth of any similar recurvature would imply that the type derives from a 
> > > very LARGE troodontid.)
> > > 2. *Troodon formous* is incomparable to other taxa, regardless of whether 
> > > the tooth is premaxillary, maxillary, or dentary in placement. Other DPF 
> > > specimens lack the comparable morphology with which to say how it can be 
> > > compared to other, less toothy and more leggy specimens. In specimens 
> > > which have dentition preserved _in situ_, the mesial carinae are 
> > > nonserrated. While this factor alone results in an autapomorphic feature, 
> > > it is based solely on the absence of detailed placement of the scores 
> > > upon scores of "troodontid" teeth recovered.
> > >
> > > But excusing that we can leave the type at just the teeth, this means the 
> > > taxonomic complexity of other forms must increase:
> > > 3. *Stenonychosaurus inequalis* and *Polyodontosaurus grandis* should be 
> > > split off, and made "distinct" due to incomparable types.
> > >
> > > But I doubt you will split the forms off. It will be "easier" to keep 
> > > them in one lumped container. That aside, my discussion stresses 
> > > precisely the problem that if you "[c]ode it as an ambiguously placed 
> > > tooth," then it "is still going to place it with derived troodontids." 
> > > You will gain decreased levels of diversity and more ambiguity with this. 
> > > An autapomoprhy like large mesial serrations relative to tooth size won't 
> > > work well when it's the only taxon in its range, and moreover pulls 
> > > "Troodon formosus" _sensu lato_ into pieces. What you will get will no 
> > > longer be "derived troodontids." It will be a big mess with likely 
> > > polytmous results. It doesn't help your case that the current "clean" 
> > > resolution in "derived troodontids" exists is largely a result of 
> > > presuming, as people have been doing, that "Troodon formosus" is the 
> > > useful term to encapsulate all of the material from the Dinosaur Park, 
> > > Judith River, Lance, Hell Creek, Two Medicine, and Prince Creek 
> > > Formations. That some of these teeth, as well as the divergent teeth of 
> > > "taxa" such as *Paronychodon lacustris* et al., may belong to a few taxa 
> > > but are themselves so divergent has to be taken into consideration.
> > >
> > > And this is to retain useage of *Troodontidae* because the presumption 
> > > must be that it's useful _enough_, regardless of the problems of the type 
> > > specimen.
> > >
> > > I would advocate a neotype, from which the Two Medicine Formation 
> > > material should be exemplary, especially as it is almost certainly the 
> > > basis for most of the TWG codings on the taxon in recent years, 
> > > supplemented by the cranial material from the Dinosaur Park Formation. 
> > > Remove the latter from the complex, describe the new material, and 
> > > petition to have a neotype designated. Otherwise, _abandon usage of 
> > > *Troodon formosus*_.
> > >
> > > Cheers,
> > >
> > > Jaime A. Headden
> > > The Bite Stuff (site v2)
> > > http://qilong.wordpress.com/
> > >
> > > "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
> > >
> > >
> > > "Ever since man first left his cave and met a stranger with a
> > > different language and a new way of looking at things, the human race
> > > has had a dream: to kill him, so we don't have to learn his language or
> > > his new way of looking at things." --- Zapp Brannigan (Beast With a 
> > > Billion Backs)
> > >
> > >
> > > ----------------------------------------
> > > > Date: Sat, 15 Oct 2011 16:35:50 -0700
> > > > From: mickey_mortimer111@msn.com
> > > > To: dinosaur@usc.edu
> > > > Subject: RE: tiny-armed theropods
> > > >
> > > >
> > > > Of course Troodon's holotype is a premaxillary tooth, but it doesn't 
> > > > matter. Code it as an ambiguously placed tooth, and the combination of 
> > > > large serrations, constricted base, high recurvature, low DSDI, low 
> > > > crown height, etc. is still going to place it with derived troodontids. 
> > > > Size is irrelevent since no other remains have to be referred to 
> > > > Troodon for my point to be valid. Keep only the holotype in the taxon 
> > > > for all I care. This also makes the rest of your discussion moot. It 
> > > > doesn't matter if Troodon formosus is a diagnostic taxon known from 
> > > > multiple individuals, a nomen dubium known only from a tooth, or even 
> > > > if nobody ever tried to name ANSP 9259 or consider its relationships to 
> > > > other reptiles. We can still include the tooth in a phylogenetic 
> > > > analysis, and it still represents a real once-living animal, contra 
> > > > Tim's claim.
> > > >
> > > > Mickey Mortimer
> > > >
> > > > ________________________________
> > > > > From: qi_leong@hotmail.com
> > > > > To: mickey_mortimer111@msn.com; tijawi@gmail.com; dinosaur@usc.edu
> > > > > Subject: RE: tiny-armed theropods
> > > > > Date: Sat, 15 Oct 2011 14:22:54 -0600
> > > > >
> > > > > Mickey Mortimer wrote:
> > > > >
> > > > > <Troodon formosus is a real animal, diagnostic holotype or not. There
> > > > > was a living organism which the type tooth of Troodon belonged to, and
> > > > > this individual can be included in a phlogenetic analysis, regardless
> > > > > of whether additional individuals could be assigned to its species.>
> > > > >
> > > > > Ah, but here's the rub:
> > > > >
> > > > > What, exactly, does ANSP 9259 correspond to? It's been hypothesized to
> > > > > be a premaxillary crown, but is quite large, and is closer in size to
> > > > > the maxillary crowns of other "like-sized" troodontids from the Late
> > > > > Campanian-Early Maastrichtian to which it has been comparable. It is
> > > > > more peculiar, true, in having large serrations on the mesial carina,
> > > > > and in this it differs from other taxa (although similar teeth have
> > > > > shown up in the Dinosaur Park Formation and somewhat similar teeth in
> > > > > the Prince Creek Formation). In an explicit level of comparison, two
> > > > > things are true:
> > > > >
> > > > > 1. The tooth differs from virtually all other "troodontid" teeth.
> > > > > 2. It is impossible -- currently, although I exaggerate only somewhat
> > > > > -- to tell which portion of the jaw the tooth belongs to.
> > > > >
> > > > > One way to qualify this is to render unto the Judith River Formation
> > > > > taxon a unique name, and this can be done by also including all other
> > > > > troodontid material from the Late Campanian strata under the same
> > > > > nominal "umbrella" of *Troodon formosus*. Another is to render all
> > > > > previously named forms for which comparison cannot be made readily
> > > > > different names. The latter is somewhat interesting, because unlike 
> > > > > the
> > > > > former, it presumes that diversity is present and can be quantified,
> > > > > rather than presuming that "diversity" is a ghost of the imagination
> > > > > (as some famous paleontologists would have it). Lumping the range of
> > > > > Late Campanian-Early Maastricthian troodontid forms into the game
> > > > > "genus-species" couplet has its perks when you are trying to reduce 
> > > > > the
> > > > > actual "apparent" diversity of taxa, while recognizing diversity can 
> > > > > be
> > > > > done merely through species under the same "genus" umbrella. This is
> > > > > why Varricchio and Horner et al. continue to use "Troodon" for the
> > > > > various undescribed specimens under their care, despite never
> > > > > describing the material or making an explicit comparison or referral.
> > > > >
> > > > > The other way to qualify this is to make all explicit material that
> > > > > lacks definitive comparability different taxa, or "not suitable for
> > > > > taxonomy," unique forms. *Troodon formosus* _is_ unqiue, does
> > > > > correspond to an actual animal, although I have yet to hear a
> > > > > qualification that has passed muster on precisely what it applies to
> > > > > and how you can tell it's synonymous with its various presumed
> > > > > synonyms. This leaves us with splitting it from all of those synonyms,
> > > > > and rendering the form to ANSP 9259. When this happens, if it happens
> > > > > and is taken in any seriousness, is a plethora of troodontid taxa
> > > > > rescued from the presumptions of synonymy and "an immense explosion in
> > > > > taxonomy" of troodontid forms. An antithesis of the theory that taxa
> > > > > should be shrinking and weren't all that diverse to begin with!
> > > > >
> > > > > This is rendered all the more significant when you consider than we 
> > > > > can
> > > > > explicitly distinguish (or could have, once) multiple taxa from
> > > > > braincases, frontoparietal pairs, and dentaries from the Dinosaur Park
> > > > > Formation and Horseshoe Canyon Formation. This coupled with the
> > > > > distinct tooth from the Judith River Formation, the apparently larger
> > > > > forms from the Prince Creek Formation and *Talos sampsoni* from the
> > > > > Kaiparowitz Formation stresses that, unless they should all be dumped
> > > > > into *Troodon formosus*, we are _UNDERrepresenting_ taxonomy, not
> > > > > presuming correctly in just one form.
> > > > >
> > > > > Cheers,
> > > > >
> > > > > Jaime A. Headden
> > > > > The Bite Stuff (site v2)
> > > > > http://qilong.wordpress.com/
> > > > >
> > > > > "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
> > > > >
> > > > > "Ever since man first left his cave and met a stranger with a 
> > > > > different
> > > > > language and a new way of looking at things, the human race has had a
> > > > > dream: to kill him, so we don't have to learn his language or his new
> > > > > way of looking at things." --- Zapp Brannigan (Beast With a Billion
> > > > > Backs)
> > > >
> > >
> >
>