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Nannotyrannus a juv-ie?



> Tom Holtz <tholtz@geochange.er.usgs.gov> writes:
snip...


>One problem is that fused sutures are not
>always indicative of the final growth stage - for example, some bird
>species continue to grow after their skulls are fused up.


 The only "final growth stage" for dinosaurs that I have heard of is _more_
growth.
 
Like living crocodyllians, dinosaurs continued to grow their entire
lives.  The concepts of sexual maturity, and old
age are separate and distinct.  For instance, Dave Varriochino
(spelling.. sorry Dave) at MOR found that Troodon reached sexual maturity at
3 to 5 years.  But increased bone mass probably
continued throughout Troodon's life.  We don't know how long Troodon lived.
We may find that extremely old individuals were only slightly larger than a
sexually mature individual who was still a whipper-snapper.  But, in any
case, the very old individual would be larger.  Mammals have a "final growth
stage"; it occurs in old age when we start _losing_ bone mass.  But, unless
there is new information out on dinosaur growth, dinosaurs kept on growing
bone mass as they got very old.  The only things that stopped when they
reached sexual maturity were _rapid_ bone growth and the development of
abundant vascularization and secondary osteons.

In the case of Nanotyrannus, the closed skull sutures only indicate sexual
maturity.  That would make it a young adult at the least.  If the skull
sutures are _obliterated_, that is another story.  The animal may be very
old.  I don't have the Bakker et.al paper in _Hunteria_, but I heard Bakker
on T.V. refer to the sutures as "tightly knit".  That is not the same thing
as saying the sutures are "fused", but I could be unnecessarily splitting 
hairs. 
I once saw a CAT scanned image of the skull, and, yes, it is mostly
plaster in places, although the interior of the braincase looked pretty
intact.