Dinosaurs: Ancient Fossils, New Discoveries California Academy of Sciences Dinosaurs - Ancient Fossils, New Discoveries


How did Dinosaurs Really Move?

Not all dinosaurs were big, but the biggest ones outweighed anything that walks the Earth today. How they really moved, while supporting their massive necks and tails, has puzzled the curious for nearly 200 years.

Today, the scientific field of biomechanics is making great headway providing answers to these questions. Experts examine fossils then compare their findings with the principles of physics and engineering revealed by studying the biological movement and musculature of animals. As a result, they are able to piece together a highly accurate sense of motion, which when combined with computers can bring scientifically accurate representations of Dinosaur movement to life.

:: Learn more about sauropod biomechanics at AMNH ::

from AMNH video
© 2005
from AMNH video
© 2005

Vertebrates have similar muscle tissue

One thing scientists know is all vertebrates have a common ancestor, because they all have similar muscle tissue; under a microscope, it's difficult to tell the muscle of a crocodile from that of a mouse or an elephant. As a result of these similarities, scientists think that the muscles of living animals hold clues to the muscles of dinosaurs.

How fast did Tyrannosaurus rex really run?

Dinosaur Exhibit: T. rex simulator
© 2005 AMNH
By studying living animals, such as chickens and humans, researchers have figured out how much leg muscle it takes for an animal to run fast. Then they applied their findings to extinct dinosaurs, varying factors such as posture and weight, which affect movement.

Their results? A sprinting T. rex was a physical impossibility. While a small theropod could run fairly quickly, a six-ton tyrannosaur would have required about three tons of leg muscle to reach speeds of 70 kilometers (45 miles) per hour!

An old-fashioned barnyard chicken is fairly fast. Like any animal, it owes its speed partly to muscle anatomy. The muscles in each leg represent up to 10 percent of a chickenís body weight. In fact, chickens are overbuilt for speed: an animal of a chicken's weight and shape could run fast with only half that amount of leg muscle.

The scientists who created the computer model of T. rex decided to enlarge a speedy chicken to T. rex's size while keeping its design the same, a process called scaling up. The result? A 6,000 kilogram (13,000-pound) chicken would need fantastically muscular legs just to walk. Instead of 10 percent, a running mega-fowl would need 62 percent of its body weight as muscle in each huge limb, which is a mathematical and biological impossibility.

:: Learn more about theropod biomechanics at AMNH ::

Bigger Animals Run with Straight Legs

Studying elephants in trackways research
From AMNH video © 2005
Stand with bent legs while you count slowly to 10. Feel how tired your legs get? It takes 50 percent more energy to stand or move with bent legs than with legs held comfortably straight. Some researchers think T. rex—170 times heavier than the average 10-year-old—moved about on straight legs, as elephants do, to conserve energy.

Elephants and rhinos walk with straighter legs than small, fast animals do, because it conserves energy.

Attaining a weight of 1,000 kilograms (2,200 pounds) was an important milestone in the life of a young tyrannosaur. Below that weight, the animal could move fairly fast; above it, life shifted into the slow lane.

Fast running would have been useful to a juvenile dinosaur. The young are more vulnerable to predators than are their full-grown parents; speed might have helped to offset the risks of small size.

Elephants are capable of their fastest speeds at about age two. Still relatively small at that age, they are vulnerable to predators, so speed may provide a slight advantage.

:: Learn more about dinosaur biomechanics at AMNH ::

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