Allosaurus - a smaller cousin of the mighty T rex - fed on its prey in a manner similar to modern-day falcons, a new study has found.
While the Tyrannosaurus rex thrashed its massive head from side to side to dismember prey, the Allosaurus was a 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 like a falcon that recruited the neck and body to strip flesh from the bones.
"Many people think of Allosaurus as a smaller and earlier version of T rex, but our engineering analyses show that they were very different predators," said Ohio University paleontologist Eric Snively, lead author of the study.
The researchers started with a high-resolution cast of the five-foot-long skull plus neck of the 150-million-year-old predatory theropod dinosaur Allosaurus.
They CT-scanned the bones at O'Bleness Memorial Hospital in Athens, which produced digital data that the authors could manipulate in a computer.
They ran sophisticated simulations of the head and neck movements Allosaurus made when attacking prey, stripping flesh from a carcass or even just looking around.
The anatomical structure of modern-day dinosaur relatives, such as birds and crocodilians, combined with tell-tale clues on the dinosaur bones, allowed the team to build in neck and jaw muscles, air sinuses, the windpipe and other soft tissues into their Allosaurus 3D computer model.
A key 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.
"This neck muscle acts like a rider pulling on the reins of a horse's bridle. 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," Snively said.
The 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."
"Allosaurus 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.
In the 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.
The study was published in journal Palaeontologia Electronica.
