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-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of MariusRomanus@aol.com >Gettin Gigi With It: Part
1
> >Is this topic uncomfortable for some people? I mean, apparently the defense mechanism is to make fun of it whenever it >surfaces on the DML.... WHY is that? My
comments have NOTHING to do with a mega-paleo box-office flop. My heart
>couldn't care less. I'm not interested in a
rip off of "Galdiator" with Tyrannosaurus rex starring instead of Russell
Crowe.
Well, it is not uncomfortable per se; it simply SEEMS
at first glance to be a non-scientific issue, of the caliber of "which would win
if they got in a fight, Superman or Captain Marvel". It is curious that
nobody asks the question "which was more powerful, Tenontosaurus or
Muttaburrasaurus", for example...
Firstly, as I mentioned in my posting, one needs to
define what one means by "powerful". Do you mean "force generated by
jaws"? "Muscular strength of neck"? "Pulling
ability"?
(By the same token, some of the other features
discussed, such as gracility, also have to be narrowed down: tyrannosaurs are
demonstrably more gracile in terms of their hindlimbs, but arguably bulkier (or
at least more compact) in the thoracic region).
Even after a definition of "powerful" is agreed upon,
one must find the means to test it. Among the various "Holtzisms" if
mentioned on the DML through the years, one I hope people appreciate is how
very, very little of the MODERN living world has been examined for the kinds of
physical parameters we would like to know about dinosaurs. We honestly do
not have good, well-supported numbers on speed, "power", "agility" (perhaps
definable in terms of turning radii), etc., for almost all large bodied
terrestrial mammals, much less birds, lizards, etc. In fact, I would
strongly encourage people interested in some of these issues to pursue a more
modern zoological career, and then apply their discoveries to paleontology: the
scientific community is in desparate need of more R. McNeill Alexanders, Steve
Gatesy's, and the like!!
>Apparently, people are just
content to point out only height and strength....
Because for most people that is the only data they have
access too (and not the latter, even). We are, and always will be, limited
in the kind of parameters which we can examine in fossil forms. Bone
length preserves well; bone thickness less well (due to compression); muscle
size only by inference; muscle pinnation, etc., only by infererence; and so
on.
As for
your observations in the rest of the original posting, and in part 2: they are
good. They do highlight the fact the two (Tyrannosaurus and
Giganotosaurus) are differently constructed, each with different
mechanical strengths in different parts of the neck. This may be
associated with general differences in feeding behaviors between tyrannosaurs
and some other large theropods, as suggested in the following abstract from SVP
1998:
LARGE THEROPOD COMPARATIVE CRANIAL FUNCTION: A NEW “TWIST” FOR
TYRANNOSAURS HOLTZ, Thomas R., Jr., Dept. Geology, Univ. Maryland, College Park,
MD 20742 The recent discovery of relatively complete skulls of large
non-tyrannosaurid theropods, including abelisaurids (Abelisaurus,
Carnotaurus, Majungatholus) and carnosaurs
(Acrocanthosaurus, Carcharodontosaurus,
Giganotosaurus), allows greater confidence in determining which
features of the crania of tyrant dinosaurs represent allometric trends common to
large theropods, and which represent specializations of that
group. Non-tyrannosaurs retain several primitive features of carnivorous
archosaurs: a dorsoventrally deep, mediolaterally narrow (oreinorostral) skull;
bladelike serrated (ziphodont) dentition; and no ossified secondary palate. Biomechanical analyses suggest such this
plan is effective at vertical slicing, but is poorly resistant to torsional
forces. Tyrannosaurs have
proportionately wider rostra, labiolingually expanded (incrassate) teeth, and
well developed ossified secondary palates composed of medial extensions of the
premaxillae and maxillae and a large, diamond shaped rostral expansion of the
vomers. Biomechanical analyses
demonstrate that this design is more resistant to torsional forces than the
primitive condition. Further
support for a torsion-based feeding system in tyrannosaurs is indicated by the
expansion of the posterior portion of the skull, increasing neck muscle
leverage.
Thomas R. Holtz, Jr.
Vertebrate Paleontologist Department of Geology Director, Earth, Life & Time Program University of Maryland College Park Scholars College Park, MD 20742 http://www.geol.umd.edu/~tholtz/tholtz.htm http://www.geol.umd.edu/~jmerck/eltsite Phone: 301-405-4084 Email: tholtz@geol.umd.edu Fax (Geol): 301-314-9661 Fax (CPS-ELT): 301-405-0796 |