Body armor over flexible armor: how dinosaurs survived high-speed collisions.

Millions of years ago, dinosaurs were the dominant species on Earth, at least until a giant asteroid, like many other animals on the planet, led to their extinction. For centuries, scientists around the globe have been discovering dinosaur fossils and attempting to reconstruct their appearance and behaviors, as reported by Live Science.

In a new study, researchers focused on examining the armor of the ankylosaur (Borealopelta markmitchelli) and found that it was likely adapted for battles between members of the species. It is believed that the armor could withstand high-speed collisions, as evidenced by the best-preserved dinosaur fossil in the history of research.

The fossil is known to belong to a nodosaur, a herbivorous dinosaur that measured about 110-112 million years in length and lived during the early Cretaceous period. According to co-author of the study, biomechanical paleontologist Michael Habib from the University of California, the fossil is incredibly well-preserved, allowing them to assess the strength of the keratin plates and bony spikes that covered it.

Scientists believe that the dinosaur's armor could likely withstand a collision with a high-speed F150 pickup truck. Notably, researchers had previously discovered fossils of armored dinosaurs that retained only bony spikes. This is attributed to keratin—dead cells that make up structures such as hair and nails—which fossilizes poorly. Consequently, scientists hypothesized that the primary defense of armored dinosaurs came from the bony structures of the armor that remained in the fossil. It is also thought that this armor might have been covered by a thin layer of keratin, similar to a turtle's shell.

Everything changed in 2017 when an exceptionally well-preserved fossil of a newly identified nodosaur species—Borealopelta markmitchelli—was discovered in a Canadian mine. According to evolutionary biologist Emma Shachner from the University of Florida, who was not involved in the new study, the fossil is incredibly beautiful and remarkably well-preserved.

In fact, the fossil was preserved so well that scientists were able to analyze the color of the armor and even peek into the dinosaur's stomach to examine its last meal. No previous armored dinosaur had been preserved well enough to keep the keratin intact.

As a result, researchers were able to detect a layer of keratin on the bone, which was significantly thicker than previously thought—reaching up to 16 centimeters in some areas. In comparison, the keratin covering in the horn of modern cattle is only about 1.5 centimeters thick. Subsequently, scientists compared the structure and size of the keratin shells with modern species and were able to calculate the magnitude of the force that the nodosaur's armor could withstand.

Moreover, researchers also replicated synthetic nodosaur armor and tested its strength using the bite force of an acrocanthosaurus. The calculations indicated that nodosaurs could likely withstand over 125,000 joules of energy per square meter—equivalent to the force of a high-speed car collision. Scientists note that these animals were not merely "dressed" in plastic armor; essentially, they wore a vest over the plastic armor. Such an adaptation makes sense given their habitat.