Very fast, but still not supersonic

Photo: Simone Conti/Zachi Evenor The computer model of the dinosaur tail used an
Photo: Simone Conti/Zachi Evenor The computer model of the dinosaur tail used and a diplodocid.

An international research team including the Department of Biology at the University of Hamburg has used computer models and engineering methods to analyze the mobility of dinosaur tails. According to a study published in the journal Scientific Reports, the researchers found that these tails could move at speeds of more than 100 kilometers per hour. Unlike previously assumed, however, they did not reach supersonic speeds.

Diplodocids were large herbivorous dinosaurs with long necks and long tails. In a previous study, it was hypothesized that a hypothetical structure at the end of a diplodocid’s tail, similar to the end of a whip, could move faster than the speed of sound (340 meters per second) and produce a sonic boom.

To test this hypothesis, the international research team simulated the movements of diplodocid tails using a model based on five fossil diplodocid skeletons. The virtual tail model is over 12 meters long, would weigh 1,446 kilograms in real life, and consists of 82 cylinders that are supposed to represent vertebrae and are attached to an immobile virtual pelvis.

-The research was quite challenging because we had to approach the problem using two methods normally used in aerospace engineering: multibody simulation and estimation of the load capacity of the materials-, reports the study’s first author, Simone Conti of Universidade NOVA de Lisboa and Politecnico di Milano.

The researchers now tested whether their model tail could withstand the strain of moving fast enough to produce a sonic boom. To do this, they moved the base of the tail in an arc, creating a whip-like motion. They found that the thin tail could not move at a maximum speed of 340 meters per second without ripping.

They then examined three different hypothetical structures, one meter in length, attached to the end of the model tail to mimic the end of a whip. The first structure consisted of three skin and keratin segments, the second of braided keratin threads, and the third of soft tissue whose shape was modeled on a medieval tool, the flail. The result: none of the structures was able to withstand the stress of moving at 340 meters per second. Thus, both different analyses showed that the tail end of diplodocids probably could not reach supersonic speed.

The simulations suggest that diplodocid tails could only reach a maximum speed of 33 meters per second (more than 100 kilometers per hour). While this is very fast, it is more than ten times slower than the speed of sound and thus too slow to produce a sonic boom, contradicting the earlier study.

-Although the tails of the diplodocids could therefore not move fast enough to produce a sonic boom, it is likely that they could have been used as defensive weapons or in combat with other diplodocids. Whether this was in a territorial battle or in competition for reproductive partners remains speculative, of course-, says paleontologist Dr. Emanuel Tschopp, Alexander von Humboldt Research Fellow in the Department of Biology at the University of Hamburg and co-author of the study.

Original publication:

Multibody analysis and soft tissue strength refute supersonic dinosaur tail, S. Conti, E. Tschopp, O. Mateus, A. Zanoni, P. Masarati, and G. Sala, Scientific Reports, 12:19245 (2022). DOI:­’022 -21633-2