Eustreptospondylus oxoniensis
One of England's best and amazing theropods!
Phylogeny and biomechanics in theropod dinosaurs
Scaling bite force in predatory animals
Bite forces of terrestrial predatory vertebrates are shown to scale with increasing body size at a
scaling factor of 2/3. This negative allometry indicates that bite force increases less-than-proportional
to increase in body mass. This scaling factor of 2/3 can be observed in many instances
of scaling: scaling of surface area to its volume in isometric bodies is one obvious example, but
more relevant is that of muscle force with body mass. Since the contractile properties of muscle are
generally agreed to be constant throughout vertebrates with varying scale, muscle force is most
likely proportional to the physiological cross-sectional areas (PCSA) of muscles (length^2.0) and
since body mass is essentially volume (length^3.0), muscle force is proportional to body mass^2/3.
This coincidence in identical scaling factors enables us to suggest that muscle force, not the
lengths of moment arms, is the determining factor of scaling trends in bite forces. A simple
biomechanical model is used as an attempt to explain this. The model predicts that scaling factors
would be most affected by parameters with the highest dimensions: in this case, body mass (length^3.0)
and muscle force (length^2.0) but not distances (length^1.0).
Estimating PCSA in theropod dinosaurs
A study on scaling of bite force with body size in extant predators shows that the
scaling factor is most likely affected by the muscular contractile forces (see above).
These forces in turn are determined by the total number of muscle fascicles involved in the
contraction or the physiological cross-sectional areas (PCSA) of the muscles. In order to estimate
absolute bite forces accurately in extinct taxa such as dinosaurs, accurate estimations of PCSA is
crucial.
Jaw adductor muscles are extracted and measured from several species of birds and
crocodilians. Up to this point, I have dissected Brenta canadensis (Canadian goose),
Gallus domesticus (domestic chicken), Larus sp. (sea gull), Struthio camelus
(ostrich), two specimens of Buteo buteo (common buzzard) and Alligator mississippiensis
(American alligator). Data from the literature will also be used. PCSA estimated from dissections
can then be correlated with some osteological markers and a regression equation can be computed.
This will then enable us to predict PCSA from osteology - osteology is for the most part the only
indicator we have when dealing with fossil specimens.
Comparative jaw biomechanics in diapsids
Jaw biomechanics of Buteo buteo
Jaw biomechanics of Sphenodon punctatus
Jaw biomechanics of Alligator mississippiensis
Jaw biomechanics of non-avian theropods
Phylogeny of theropods
Recently, I've been part of a working group in producing a supertree of dinosaurs.
Obvously, I've been allocated the Theropoda with the exclusion of maniraptorans (a Master's student
did this chunk).
Using this phylogeny, I hope to answer (or test) certain questions;
Body size: did dinosaurs get bigger and bigger (testing Cope's Rule) or are there different
trends among clades? What is the general trend in body size in the lineage to birds?
Bite force: do different clades show different trends in bite force?
Cranial biomechanical characters: how does jaw biomechanics evolve in different clades?
