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Avetheropod Neural Spines
Just a question until I can affirm my suspicions by research:
Caudals in avetheropods appear to bear a secondary, cranial spine (I
have been preferring to use the nomenclature "secondary neural spur")
anterior to and at the base of the neural spine in non-maniraptorans,
about 7th or more posteriorly in the series; in some (e.g.,
*Bagaraatan*) this is so well-developed it might even be autapomorphic,
and for *Deltadromeus* this is mild but still unusual to look at. I see
this in the caudals of all the carnosaurs I've looked at so far, which
include just about all of the allosauroids, but is in
*Piatnitzkysaurus* (I'm not sure I agree with the latest from Tom Holtz
on the apparently non-carnosaurian nature of this animal, but hey,
there could be tons of plesiomorphies, homoplasy up the yin-yang -- you
never know....). However, in *Acrocanthosaurus* the caudal neural
spines possess in the cranial members of the series a small hook-like
spur that becomes almost a ring in a few elements (at least in the type
-- I have yet to look at Harris' new specimen, and "Fran" has yet to be
published, to my knowledge). I notice that the prezygapophyseal-spinal
lamina in these converge on the median to form the spur, but then saw
to my amazement that, unlike in other carnosaurs, this convergence of
the laminae is present in a dorsal neural spine and a posterior
cervical vertebra (Stovall and Langston, 1950).
I would like to know of any illuminating ideas, on why this is so
unique in Acro, and if possibly there isn't an homology throughout the
series to other secondary neural spurs, which don't persist to the
first few caudals in _any_ form I know of, much less in the presacral series....
Jaime A. Headden
Where the Wind Comes Sweeping Down the Pampas!!!!
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