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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)