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Re: Tyrannosaurus tail torque



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
>
>
>