Sonic boom of a jet.

© Ensign John Gay, USS Constellation, US Navy

Some sauropod tails look like whips--and the resemblance may not be coincidence. Both are long, relatively broad at the base and narrow at the tip. Recent computer models comparing sauropod tails and bullwhips has revealed a surprise: If moved in particular ways, some tails, like noisemaking whips, could reach supersonic speeds.

Apatosaurus might have swung its tail from side to side by shifting its weight or stamping its feet. The force of the huge animal's movement, traveling down the tapering structure in a wave, could have created an impressive noise.

But why would a sauropod crack the whip? Perhaps the noise was a form of warning, either to a predator or other sauropods. Or could it have been a form of display? Perhaps sauropods, like males of many species, tried to outdo one another when competing for females.

© John Gurche

Breaking the Sound Barrier

When an object moves faster than about 1,200 kilometers (over 700 miles) per hour it compresses the sound waves in front of it, creating a loud noise. The moment the tip of a bullwhip exceeds supersonic speed, we hear an explosive sonic boom.

Stupid Dinosaur Tricks?

Though some of the smaller sauropods may have been able to rear up briefly, they wouldn't have done it often. Why? For one thing, sauropods probably had very primitive balance centers in their tiny brains--and you'd hate to see a dinosaur this big fall over!