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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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