T. rex pulverized bones with an incredible amount of force | Science News for Students

T. rex pulverized bones with an incredible amount of force

A strong bite and powerful teeth let the dinosaur get at nutritious marrow and salts
Nov 12, 2018 — 6:45 am EST
a photo of the skeleton of Sue, a T. rex skeleton at Chicago's Field Museum, against a white background

T. rex didn’t have the ability to clamp its jaws to crush bones, like some mammals do today. Instead, it used its powerful bite and strong teeth to pulverize the bones of its prey.

Connie Ma/Wikimedia Commons (CC BY-SA 2.0)

ALBUQUERQUE, N.M. — A powerful bite, strong teeth and repeated crunching. This is what allowed Tyrannosaurus rex to pulverize the bones of its prey. That’s the conclusion of a new analysis of the giant predator’s chomp.

Bones have an inner cavity containing marrow and other nutrients. To access those goodies, some animals crunch through the dense outer protective layer of bone. Most do so by clamping their jaws together to crush the bone. Some meat-eating mammals, like spotted hyenas and gray wolves, can do this. But bone-crushing is unknown among living reptiles. Their upper and lower teeth simply don’t fit together in a way that allows them to clamp. Instead, most modern reptilian predators swallow bones whole to get at the nutrients.

Fossil evidence suggests tyrannosaurs, including T. rex, somehow pulverized the bones of their prey. But their teeth didn’t fit together like mammals’ do. So how did they crush those bones?

Paul Gignac and Gregory Erickson teamed up to figure this out. Gignac studies body structure as an anatomist at Oklahoma State University in Tulsa. And Erickson is a vertebrate paleontologist at Florida State University in Tallahassee. That means he specializes in fossils of animals with backbones.

Together, the two looked at fossils of the teeth from T. rex and at this dino’s prey. The duo also measured the bite strength of living dino relatives. For that, they studied birds — the only living dinosaurs. They also studied crocodiles, which are dinosaurs’ closest living relatives. From these, the researchers estimated the chomping force of a T. rex bite. They also predicted how much pressure the dinos’ teeth could exert at their tips.

a photo of the head of Sue the T. rex, showing her giant teeth
My what big choppers. This closeup shows the bite of Sue, a T. rex skeleton on display at Chicago’s Field Museum.
Jill Sakai

A single bite could deliver a force up to 34,000 newtons, they now estimate. (A newton is a measure of force.) That’s more than twice the bite strength of a croc, the strongest living chomper. They also showed that the dinos’ teeth could exert intense pressure at their tips. That pressure could reach up to 3 billion pascals, the scientists estimate. (A pascal measures pressure, or the amount of force applied on an area.)

T. rex could crush bones thanks to that bite strength and the shape of its teeth, the scientists say. The massive pressure from those teeth helped create cracks that weakened bones. T. rex would also chomp over and over in the same spot to break bones.

These advantages may have helped the predator get the most out of its prey. Gignac and Erickson described their findings on October 20 here, in New Mexico, at the annual meeting of the Society for Vertebrate Paleontology.

Power Words

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anatomy     See (adj. anatomical) The study of the organs and tissues of animals. Or the characterization of the body or parts of the body on the basis of its structure and tissues. Scientists who work in this field are known as anatomists.

annual     Adjective for something that happens every year.

cavity     (in geology or physics) A large rigid pocketlike structure. (in biology) An open region pocketlike structure surrounded by tissues.

dinosaur     A term that means terrible lizard. These ancient reptiles lived from about 250 million years ago to roughly 65 million years ago. All descended from egg-laying reptiles known as archosaurs. Their descendants eventually split into two lines. For many decades, they have been distinguished by their hips. The lizard-hipped line are believed to have led to the saurichians, such as two-footed theropods like T. rex and the lumbering four-footed Apatosaurus (once known as brontosaurus). A second line of so-called bird-hipped, or ornithischian dinosaurs, appears to have led to a widely differing group of animals that included the stegosaurs and duckbilled dinosaurs. But a new 2017 analysis now calls into question that characterization of relatedness based on hip shape.

force     Some outside influence that can change the motion of a body, hold bodies close to one another, or produce motion or stress in a stationary body.

fossil     Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.

mammal     A warm-blooded animal distinguished by the possession of hair or fur, the secretion of milk by females for feeding their young, and (typically) the bearing of live young.

marrow     (in physiology and medicine) Spongy tissue that develops inside of bones. Most red blood cells, infection-fighting white blood cells and blood platelets form within the marrow.

newton     A unit of force named for Sir Isaac Newton, a 17th century English physicist and mathematician. One newton is an amount that would give a mass of one kilogram an acceleration of one meter per second per second.

nutrient     A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.

paleontology     The branch of science concerned with ancient, fossilized animals and plants. The scientists who study them are known as paleontologists.

pascal     A unit of pressure in the metric system. It is named for Blaise Pascal, the 17th century French scientist and mathematician. He developed what became known as Pascal’s law of pressure. It holds that when a confined liquid is pressed, that pressure will be transmitted throughout the liquid in all directions, without any losses.

predator     (adjective: predatory) A creature that preys on other animals for most or all of its food.

pressure     Force applied uniformly over a surface, measured as force per unit of area.

prey     (n.) Animal species eaten by others. (v.) To attack and eat another species.

reptile     Cold-blooded vertebrate animals, whose skin is covered with scales or horny plates. Snakes, turtles, lizards and alligators are all reptiles.

tyrannosaur     A line of meat-eating dinosaurs that began during the late Jurassic Period, about 150 million years ago. These species persisted into the late Cretaceous Period, about 65 million years ago. The best known member of these species: the late Cretaceous’ Tyrannosaurus rex, a 12-meter (40 foot) long top predator of its time.

vertebrate     The group of animals with a brain, two eyes, and a stiff nerve cord or backbone running down the back. This group includes amphibians, reptiles, birds, mammals and most fish.


Meeting: P.M. Gignac and G.M. Erickson. The biomechanics behind extreme osteophagy in Tyrannosaurus rex. Society of Vertebrate Paleontology 78th Annual Meeting. October 20, 2018. Albuquerque, New Mexico.