RELEASE TUESDAY, 21 MAY 2013, 2:00 PM EDT
more like a falcon than a crocodile, new study finds
Engineering, anatomy work reveals differences in dinosaur
Ohio (May 21, 2013)—The mighty T. rex may have thrashed
its massive head from side to side to dismember prey, but a new
study shows that its smaller cousin Allosaurus was a more
dexterous hunter and tugged at prey more like a modern-day
one size doesn’t fit all when it comes to dinosaur feeding
styles,” said Ohio University paleontologist Eric Snively, lead
author of the new study published today in Palaeontologia
Electronica. “Many people think of Allosaurus as a
smaller and earlier version of T. rex, but our
engineering analyses show that they were very different
a diverse team of Ohio University researchers, including experts
in mechanical engineering, computer visualization and dinosaur
anatomy. They started with a high-resolution cast of the
five-foot-long skull plus neck of the 150-million-year-old
predatory theropod dinosaur Allosaurus, one of the best
known dinosaurs. They CT-scanned the bones at O’Bleness Memorial
Hospital in Athens, which produced digital data that the authors
could manipulate in a computer.
mechanical engineer John Cotton applied a specialized
engineering analysis borrowed from robotics called multibody
dynamics. This allowed the scientists to run sophisticated
simulations of the head and neck movements Allosaurus
made when attacking prey, stripping flesh from a carcass or even
just looking around.
engineering approach combines all the biological data—things
like where the muscle forces attach and where the joints stop
motion—into a single model. We can then simulate the physics and
predict what Allosaurus was actually capable of doing,”
said Cotton, an assistant
professor in the Russ College of Engineering and Technology.
out how Allosaurus de-fleshed a Stegosaurus, the
team had to “re-flesh” Allosaurus. The anatomical
structure of modern-day dinosaur relatives, such as birds and
crocodilians, combined with tell-tale clues on the dinosaur
bones, allowed Snively and anatomists Lawrence Witmer and Ryan
Ridgely to build in neck and jaw muscles, air sinuses, the
windpipe and other soft tissues into their Allosaurus 3D
bones simply aren’t enough,” said Witmer, Chang Professor of
Paleontology in the Heritage College of Osteopathic Medicine and
principal investigator on the National Science Foundation’s
Visible Interactive Dinosaur Project that provided funding for
this research. “We need to know about the other tissues that
bring the skeleton to life.”
finding was an unusually placed neck muscle called longissimus
capitis superficialis. In most predatory dinosaurs, such as
T. rex, which Snively studied previously, this muscle passed
from the side of the neck to a bony wing on the outer back
corners of the skull.
muscle acts like a rider pulling on the reins of a horse’s
bridle,” explained Snively. “If the muscle on one side
contracts, it would turn the head in that direction, but if the
muscles on both sides pull, it pulls the head straight back.”
analysis of Allosaurus revealed that the longissimus
muscle attached much lower on the skull, which, according to the
engineering analyses, would have caused “head ventroflexion
followed by retraction.”
was uniquely equipped to drive its head down into prey, hold
it there, and then pull the head straight up and back with the
neck and body, tearing flesh from the carcass … kind of like how
a power shovel or backhoe rips into the ground,” Snively said.
animal world, this same de-fleshing technique is used by small
falcons, such as kestrels. Tyrannosaurs like T. rex, on
the other hand, were engineered to use a grab-and-shake
technique to tear off hunks of flesh, more like a crocodile.
team’s engineering analyses revealed a cost to T. rex’s
feeding style: high rotational inertia. That large bony and
toothy skull perched at the end of the neck made it hard for
T. rex to speed up or slow down its head or to change its
course as it swung its head around.
had a relatively very light head, which the team discovered as
they restored the soft tissues and air sinuses.
Having a lot
of mass sitting far away from the axis of head turning, as in
T. rex, increases rotational inertia, whereas having a
lighter head, as in Allosaurus, decreases rotational
inertia, the researchers explained. An ice skater spins faster
and faster as she tucks her arms and legs into her body,
decreasing her rotational inertia as the mass of her limbs moves
closer to the axis of spinning.
with its lighter head and neck, was
like a skater who starts spinning with her arms tucked in,” said
Snively, “whereas T. rex, with its massive head and neck
and heavy teeth out front, was more like the skater with her
arms fully extended … and holding bowling balls in her hands.
She and the T. rex need a lot more muscle force to get
result is that Allosaurus was a much more flexible hunter
that could move its head and neck around relatively rapidly and
with considerable control. That control, however, came at the
cost of brute-force power, requiring a de-fleshing style that,
like a falcon, recruited the whole neck and body to strip flesh
from the bones.
University team will continue to use their engineering approach
to explore additional differences in dinosaur feeding styles.
scientific article is freely available (open-access) on the
Palaeontologia Electronica site (http://palaeo-electronica.org).
The research was funded by National Science Foundation grants to
Lawrence Witmer and Ryan Ridgely, as well as by the Department
of Mechanical Engineering in the Russ College of Engineering and
Technology (John Cotton and Eric Snively) and the Heritage
College of Osteopathic Medicine (Witmer, Ridgely, and Snively).
• Download the article here:
• Related images and animations can be downloaded from the
• A fact sheet can be accessed here:
(all Eastern Standard Time):
1. Eric Snively, 740-591-8928,
2. Lawrence Witmer, 740-591-7712,