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Re: Tyrannosaurus tail torque

I'm very glad to see this paper out now; awesome research!

I've been saying the same thing for a long time (see, e.g., my
Plateosaurus reconstructions and my upcoming Kentrosaurus paper). In
comparison to crocs even Plateosaurus had a proportionally much larger
CFL. Immediately visible because of the much longer haemapophyses.

What needs to be kept in mind is another factor of thicker muscles
that is often overlooked: the moment arm increases, too, so that
lateral motions of the tail can be performed with even more power
(torque = force * moment arm).


On Tue, Nov 16, 2010 at 5:26 AM, Augusto Haro <augustoharo@gmail.com> wrote:
> This would also have the consequence of a heavier tail, which would
> better equilibrate the gravity mass if the femur was closer to the
> vertical (the relatively larger the mass of the tail, the more erect
> the femur can conceivably be in an equilibrated walking/standing
> theropod).
> The further increase in the muscular mass also suggests a more
> tachymetabolic status for theropods accepting Paul's (Dinosaurs of the
> Air, 2002) idea that the limb muscular mass increases with the
> metabolic rate (to me it sounds perfectly logical, for tachymetabolic
> animals likely need greater stamina to search for more energy, and
> stamina requires a greater concentration of mitochondriae for
> locomotion in aerobical conditions common in animals with stamina, and
> mitochondriae forming a greater proportion of the muscular mass imply
> that to maintain the same force as in an animal without stamina, the
> muscular mass has to be increased).
> However, this increase can only reflect locomotor specialization, for
> example, it is evident that anurans have more larger and thicker (and
> proportionally more powerful) limb muscles than urodeles, but it is
> not evident that there is a difference in metabolic rate. In the frog
> (and probably in the turtle), the lesser mobility of the trunk may
> require more of the locomotion force to be generated by the limbs, not
> to talk about the need of more powerful muscles in jumping.
> 2010/11/15  <bh480@scn.org>:
>> From: Ben Creisler
>> bh480@scn.org
>> In case this story and ref have not been posted yet:
>> Tyrannosaurus rex tail had massive muscles.
>> http://www.physorg.com/news/2010-11-rex-big-tail-key-
>> prowess.html
>> W. Scott Persons IV, Philip J. Currie (2010)
>> The Tail of Tyrannosaurus: Reassessing the Size and
>> Locomotive Importance of the M. caudofemoralis in Non-
>> Avian Theropods
>> Anatomical Record (advance online publication)
>> DOI: 10.1002/ar.21290
>> Article first published online: 12 NOV 2010
>> Unlike extant birds and mammals, most non-avian theropods
>> had large muscular tails, with muscle arrangements
>> similar to those of modern reptiles. Examination of
>> ornithomimid and tyrannosaurid tails revealed sequential
>> diagonal scarring on the lateral faces of four or more
>> hemal spines that consistently correlates with the zone
>> of the tail just anterior to the disappearance of the
>> vertebral transverse processes. This sequential scarring
>> is interpreted as the tapering boundary between the
>> insertions of the M. caudofemoralis and the M.
>> ilioischiocaudalis. Digital muscle reconstructions based
>> on measurements of fossil specimens and dissections of
>> modern reptiles showed that the M. caudofemoralis of many
>> non-avian theropods was exceptionally large. These high
>> caudofemoral mass estimates are consistent with the
>> elevation of the transverse processes of the caudal
>> vertebra above the centrum, which creates an enlarged
>> hypaxial region. Dorsally elevated transverse processes
>> are characteristic of even primitive theropods and
>> suggest that a large M. caudofemoralis is a basal
>> characteristic of the group. In the genus Tyrannosaurus,
>> the mass of the M. caudofemoralis was further increased
>> by dorsoventrally lengthening the hemal arches. The
>> expanded M. caudofemoralis of Tyrannosaurus may have
>> evolved as compensation for the animal's immense size.
>> Because the M. caudofemoralis is the primary hind limb
>> retractor, large M. caudofemoralis masses and the
>> resulting contractile force and torque estimates
>> presented here indicate a sizable investment in
>> locomotive muscle among theropods with a range of body
>> sizes and give new evidence in favor of greater
>> athleticism, in terms of overall cursoriality, balance,
>> and turning agility. Anat Rec,, 2010. © 2010 Wiley-Liss,
>> Inc.
>> http://onlinelibrary.wiley.com/doi/10.1002/ar.21290/abstra
>> ct