Tyrannosaurus rex was a thrasher, prone to vigorously shaking its powerful, prey-packed jaws from side-to-side like a crocodile. But new simulations reveal Allosaurus was equipped to dismember its prey with a little more decorum, stripping flesh from bone not with the head-swinging motion of a croc, but the meticulous tug-tug-tug of a falcon.
Top image by Simon Farrell – for more examples of his stunning work, visit his website.
In the latest issue of Palaeontologia Electronica, a team of experts in biomechanics, computer visualization and dinosaur anatomy have produced some fantastic simulations of Allosaurus anatomy, which reveal the bird-like eating habits of the formidable predator. Led by Ohio University paleontologist Eric Snively, the researchers first performed CT scans on a high-resolution cast of an Allosaur head and neck (which you may recognize as a replica of "Big Al"):
The researchers then converted the data into a 3D model, and added musculature, a windpipe and other soft tissues to the skeletal frame. Borrowing an engineering method known as "multibody dynamics" from the field of robotics, Snively and his team conducted a series of motion simulations, which allowed them to analyze head and neck function in Allosaurus and examine their role in feeding mechanics:
Their analysis revealed that Allosaurus, unlike T. rex, had a relatively light-weight head, which, by their measurements, could be moved around with speed and precision. Snively compares the dinosaurs' differences in head-motion to the rotational inertia of a figure skater:
"Allosaurus, with its lighter head and neck, was like a skater who starts spinning with her arms tucked in," said Snively in a statement, "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 going."
The analysis also suggests that the unusual placement of a muscle called "longissimus capitis superficialis" would have enabled Allosaurus to drive its teeth downward into flesh while retracting its head, in a manner not unlike modern day falcons:
"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," said Snively, "kind of like how a power shovel or backhoe rips into the ground."
Snively and his colleagues acknowledge Allosaurus was probably not limited to a single strategy for "defleshing" its prey (side note: awesome terminology). Its dental structure, for example, suggests "forceful alternating tugs to either side of the head, as seen in Komodo dragons," would also have been effective at ripping meat from a kill.
The researchers also hypothesize that Allosaurus' ability to, in Snively's words, "power shovel or backhoe" her prey may have enabled her to brace prey with her feet, "holding flesh with the head highly flexed, and pulling up and back with their legs," in a manner similar to modern raptorial birds, like Merlins:
Photo by Steve Mills via National Geographic
"Although Allosaurus has large bladelike teeth and lacks the hooked beak of raptorial birds, similarly energetic ventroflexion may have enabled analogous behavior," write the researchers in their newly published paper. "Assessing the likelihood of such action awaits fullbody simulations that combine leg and neck function."
The researchers' work is published in the latest issue of Palaeontologia Electronica. See also the following illustration, created by Snively's team – what is hands down the single best dino/human/kestrel silhouette we've ever seen. We think it deserves a place in our ever-growing inventory of amusing journal figures: