Diplodocus was already huge - close to 90 feet long from nose to tail - but its tail wasn’t just for size. Its 80+ vertebrae got thinner and thinner the further from the body, ending in a string of tiny bones like the lash of a giant whip.
In 1997 a scientist modeled how that tail could move and got a wild answer: a properly-swung Diplodocus tail tip might break the sound barrier with a thundercrack. Twenty-five years later, a 2022 study re-ran the maths with a more realistic muscle and bone model. The verdict? The whip-thin tail bones would shatter long before the tip got anywhere near supersonic speed. The new estimate is more like 70 mph - still fast, but no sonic boom.
The tail was probably for communication, balance, and warning predators. A 70 mph slap from a 70-foot dinosaur is plenty motivating for an Allosaurus to find an easier meal.
