Another New Paper

["Jerry D. Harris" <jharris@dixie.edu>]

The third in a triumvirate of papers on ossified tendons:

Organ, C.L. 2006. Biomechanics of ossified tendons in ornithopod dinosaurs. 
Paleobiology 32(4):652-665. doi: 10.1666/05039.1.

ABSTRACT: Spinal ossified tendons are a defining character for Ornithischia, 
one of the two major clades of dinosaurs. The function of these bony rods 
has remained a mystery since their first detailed description in 1886. 
Qualitative approaches to understand ossified tendon function have resulted 
in different ecological and behavioral interpretations for ornithopod 
dinosaurs. To evaluate ossified tendon function, this study constructed 
finite element models of the vertebral column for two ornithopod taxa: 
Tenontosaurus, which shows the plesiomorphic condition of longitudinally 
arrayed tendons along the spinous processes, and Brachylophosaurus, which 
exhibits a lattice of tendons along the spinous processes. Both models 
predict that ossified tendons stiffened the vertebral column, especially the 
tail, but the derived lattice of ossified tendons in iguanodontoidean 
dinosaurs, like Brachylophosaurus, increased spinal stiffness more than the 
plesiomorphic condition. Caudofemoral muscles that retracted the hindlimb 
during locomotion attached the femur to the tail in ornithopods. Increased 
tail stiffness caused by intratendinous ossification may have influenced 
locomotion by rigidly anchoring M. caudofemoralis longus to the tail, 
thereby allowing a more forceful retraction of the hindlimb by reducing 
ventral flexion of the tail during muscle contraction. Ossified tendons may 
also have been important for storing elastic energy throughout the gait 
cycle. Moreover, the lattice of ossified tendons stiffened the trunk and 
tail nearly equally in Brachylophosaurus, indicating the evolution of a 
postural function by passively supporting the epaxial musculature in 
maintaining a horizontal vertebral column.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT  84770   USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
and     dinogami@gmail.com
http://cactus.dixie.edu/jharris/

"Trying to estimate the divergence times
of fungal, algal or prokaryotic groups on
the basis of a partial reptilian fossil and
protein sequences from mice and humans
is like trying to decipher Demotic Egyptian with
the help of an odometer and the Oxford
English Dictionary."
              -- D. Graur & W. Martin (_Trends
                  in Genetics_ 20[2], 2004)