T. Rex's Big Tail Was Its Key to Speed and Hunting Prowess
ScienceDaily (Nov. 16, 2010) — Tyrannosaurus rex was far from a plodding Cretaceous era scavenger whose long tail only served to counterbalance the up-front weight of its freakishly big head.
Rendering of T. Rex tail. (Credit: iStockphoto)
T. rex's athleticism (and its rear end) has been given a makeover by University of Alberta graduate student Scott Persons. His extensive research shows that powerful tail muscles made the giant carnivore one of the fastest moving hunters of its time.
As Persons says, "contrary to earlier theories, T. rex had more than just junk in its trunk."
The U of A paleontology student began his research by comparing the tails of modern-day reptiles like crocodiles and Komodo dragons toT.rex's tail. Persons found for that all animals in his study, the biggest muscles in the tail are attached to upper leg bones. These caudofemoralis muscles provide the power stroke allowing fast forward movement.
But Persons found T.rex had one crucial difference in its tail structure.
...
Read more here/Leia mais aqui: Science Daily
+++++
The Tail of Tyrannosaurus: Reassessing the Size and Locomotive Importance of the M. caudofemoralis in Non-Avian Theropods
W. Scott Persons IV, Philip J. Currie
The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology
Keywords:
dinosaurs; Tyrannosaurus; locomotion; tail musculature; biomechanics
Abstract
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. caudofemoralisis 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.
+++++
