Tyrannosaurid neck muscles and feeding style

[Guy Leahy <xrciseguy@sbcglobal.net>]

Anat Rec (Hoboken). 2007 Aug;290(8):934-57. Links
Functional variation of neck muscles and their
relation to feeding style in Tyrannosauridae and other
large theropod dinosaurs.Snively E, Russell AP.
Department of Biological Sciences, University of
Calgary, Calgary, Alberta, Canada.

Reconstructed neck muscles of large theropod dinosaurs
suggest influences on feeding style that paralleled
variation in skull mechanics. In all examined
theropods, the head dorsiflexor m. transversospinalis
capitis probably filled in the posterior dorsal
concavity of the neck, for a more crocodilian- than
avian-like profile in this region. The tyrannosaurine
tyrannosaurids Daspletosaurus and Tyrannosaurus had
relatively larger moment arms for lateroflexion by m.
longissimus capitis superficialis and m. complexus
than albertosaurine tyrannosaurids, and longer
dorsiflexive moment arms for m. complexus. Areas of
dorsiflexor origination are significantly larger
relative to neck length in adult Tyrannosaurus rex
than in other tyrannosaurids, suggesting relatively
large muscle cross-sections and forces. Tyrannosaurids
were not particularly specialized for neck
ventroflexion. In contrast, the hypothesis that
Allosaurus co-opted m. longissimus capitis
superficialis for ventroflexion is strongly
corroborated. Ceratosaurus had robust insertions for
the ventroflexors m. longissimus capitis profundus and
m. rectus capitis ventralis. Neck muscle morphology is
consistent with puncture-and-pull and powerful shake
feeding in tyrannosaurids, relatively rapid strikes in
Allosaurus and Ceratosaurus, and ventroflexive
augmentation of weaker jaw muscle forces in the
nontyrannosaurids.