In the hot, dry Hell Creek Formation of South Dakota, scientists may have found the answer to one of Tyrannosaurs rex’s most pressing secrets.

Anyone who has ever owned a plastic dinosaur is familiar with the popular theory that T. rex was a predacious killing machine. The theory goes that it used its 15 feet of height, 40 feet of length, powerful jaws, and treelike legs to take down the whale-sized herbivores that otherwise would have had nothing to fear.

There is, of course, the other theory, much less popular, that T. rex was actually a scavenger. Like a vulture, it lived the much easier lifestyle of searching for food that was already dead and generally keeping the landscapes of the late Cretaceous clean. Its role was much more like that of garbage disposal than the tyrant of the ecosystem.

While it lacks Hollywood appeal, there is more than a little evidence pointing towards a scavenger lifestyle for T. rex. Unlike most living predators, which often rely upon a keen sense of sight, T. rex had small, beady eyes which may not have been good enough for hunting. However, the olfactory lobes of its brain are thought to have been very large, meaning its sense of smell was acute, an attribute very useful to a scavenger.

Perhaps most convincing, are the doubts about how fast T. rex could have run. The six ton dinosaur may simply not have been able to catch fleeing prey. Its legs, while long, may actually be structured better for walking long distances (searching for carrion) than for short sprints (chasing prey).

The first Tyrannosaurus rex skeleton was described by scientists in 1905 and the debate about its role in the prehistoric ecosystem has been raging ever since. With convincing arguments on both sides, it was easy to despair of ever coming to a conclusive conclusion. As Greg Erickson, professor of anatomy and vertebrate paleobiology at Florida State University remarked, “Bones fossilize really well, but unfortunately behavior doesn’t.”

However, Robert A. DePalma of the Department of Paleontology at the Palm Beach Museum of Natural History, David A. Burnham, Larry D. Martin, and Bruce M. Rothschild of the Division of Vertebrate Paleontology at University of Kansas, and Peter L. Larson of Black Hills Institute of Geological Research have published a paper in Proceedings of the National Academy of Sciences of the United States of America that finally proves T. rex attacked living prey.

While dinosaur bones showing damage from T. rex teeth are common, proof that these animals were alive when the damage happened was non-existent until Burnham and his associates made their discovery.

They report on the tail bones of a hadrosaur, a type of duck billed dinosaur, which had received damage but had clearly begun to heal, proving that the creature was alive when it was bitten. Also difficult to discover is proof that T. rex was responsible for the attack, and not some other predator. Luckily, the hadrosaur’s attacker is also clear beyond a doubt: the T. rex tooth was still lodged inside the healing bone.


T. rex tooth crown embedded between hadrosaur vertebrae and surrounded by bone overgrowth. Image courtesy of Fallon Cohen (Palm Beach Museum of Natural History).

Even this concrete evidence that T. rex did do some hunting will probably not lay the debate completely to rest. Like hyenas or other modern day predators, T. rex probably did a little hunting and a little scavenging. The question really is which it did more.

However, Burnham and his colleges have all but settled the debate over whether Tyrannosaurus rex was capable of hunting, even if its preferences still remain a mystery. T. rex fans can breathe a sigh of relief. At least one childhood fantasy has proven true.

Read the study, “Physical evidence of predatory behavior in Tyrannosaurus rex“, in the journal Proceedings of the National Academy of Sciences.

The Paleontological Research Institution, Ithaca, New York, is pleased to sponsor Paleontology content for This View of Life. Founded in 1932, PRI has outstanding programs in research, collections, and publications, and is a national leader in development of informal Earth science education resources for educators and the general public.

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Published On: September 12, 2013

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