Diplodocids, large long-necked herbivorous dinosaurs including diplodocus and brontosaurus, could whip their tails at speeds of up to 33 meters per second (more than 100 kilometers per hour). The finding, published in ‘Scientific Reports’, contradicts a previous study that proposed that a hypothetical structure attached to the end of the tail of these animals – similar to a lock at the end of a whip – could move faster than the speed of sound ( 340 meters per second) and create a small sonic boom.
Researchers at the Milan Polytechnic simulated diplodocid tail movements using a model based on five fossilized specimens. The model’s tail is more than 12 meters long, weighs 1,446 kilograms and consists of 82 cylinders, representing vertebrae, attached to an immovable base of the hip bone.
When the base of the tail moves in an arc, it generates a whip-like movement with a maximum speed of 33 meters per second, more than ten times slower than the speed of sound in standard air and too slow to create a supersonic boom.
The authors tested whether their model’s tail would be able to withstand the stress of moving fast enough to create a supersonic boom. They found that the thin, whip-like tail could not move at a top speed of 340 meters per second without breaking.
The end of a whip
The authors then tested whether adding three different hypothetical meter-long structures, which mimic the end of a whip, to the end of the model’s tail could allow it to reach the speed of sound without breaking.
The first structure consisted of three segments made of skin and keratin, the second consisted of braided keratin filaments, and the third had a flail-like structure composed of soft tissues. None of the structures could withstand the effort of moving at 340 meters per second without breaking the tail.
Together, the findings suggest that the tails of diplodocus and more were not capable of moving fast enough to create a small supersonic boom. However, the authors speculate that it is possible that these dinosaurs could still use their tails as a defensive weapon or to fight with their conspecifics.