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RE: Dinosaurs Decoded

David Marjanovic wrote, referring to Brian Switek's conversation with Bob 

<"Good rebuttal"? The first half is nothing but an argument from personal 
incredulity(*), which is now partly falsified by the discovery that 
"*Torosaurus*" is the adult stage of *Triceratops*.>

  Pardon me, but the study shown and the abstract details (from this 
non-attendee to Bristol's (and nonAmerica's first ever) SVP[SVPCA] project that 
*Torosaurus* trends as far as *Triceratops* trends, only it seems even 
further.  It is reasonable to assume that, based on a lack of clear juveniles 
of species of *Torosaurus*, absence of subadults in species of *Torosaurus*, or 
indications that adults of species of *Torosaurus* are always larger than 
concordant species of *Triceratops* (without the crest taken into account), one 
could project *Torosaurus* is the late-growth stage of *Triceratops*.  Several 
questions arise, however: 

1) Do we have any implied juveniles of *Torosaurus* AND do we know that the 
implied juveniles of *Triceratops* belong to that taxon? 

2) Can we also assume that *Triceratops* and *Torosaurus* share identical 
growth trajectories and that this will account for the similarities and seeming 
identical trends in the two? 

3) If this were the case, would species of *Torosaurus* be sunk into species of 
*Triceratops*, or would the species list of *Triceratops* (including through 
synonymy) simply inflate? 

4) What is the morphological ground for sinking the one into the other, if 
*Torosaurus* can be differentiated (all species together) by a feature of the 
frill that no specimen of *Triceratop*s possesses? 

5) Even if this were a growth stage, explicit intermediates should be present.  
That several *Triceratops* skulls produce frills that are quite short at large 
size, very, very broad and with upturned caudal margins (forming a saddle 
shape) should we also not assume that some species did NOT continue this trend 
and (if so) this would be an aspect of morphology that would conflict with the 
concept of sinking the taxa?

It should be noted to those who are already asserting that the taxa have been 
sunk that no such thing has occured. One group has, so far, only proposed the 
concept (compellingly, I might add -- I have no stick with the study and if 
this were the case it helps resolve some issues of *Torosaurus* rarity without 
apparent juveniles, not that that hasn't always been an issue for other "adults 
only" taxa for which juveniles have not been known) and as a result, this is a 
greta topic for debate and respective studies to observe whether the trend 
proposed is detailed enough to warrent synonymization.


Jaime A. Headden

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