Tyrannosaurus tail torque

[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