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RE: tiny-armed theropods



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)
>