Flesh-eating theropods were extremely fast

Through an analysis of fossil footprint tracks, a new study led by the University of La Rioja has found that, about 100 million years ago in what is now La Rioja province in northern Spain, two bipedal meat-eating theropods reached running speeds of almost 45 kilometers per hour.

About 35 years ago, researchers discovered a few three-toed dinosaur footprints in La Rioja. Recently, further excavations at the site revealed more prints forming two short trails. The analysis of the footprints suggest that they were made by two medium-sized dinosaurs, each about four to five meters long and two meters tall, belonging to either the spinosaur or the carcharodontosaur family of predatory therapods. 

By analyzing the distance between consecutive footprints (the stride length), a research team from the University of La Rioja has found that the two dinosaurs were incredibly fast, reaching speeds of up to 45 kilometers per hour. Moreover, abrupt changes in speed suggested that the creatures switched directions as they ran.

“High-velocity trackways are very scarce around the world,” said study senior author Angélica Torices, a paleontologist at the University of La Rioja. According to her, speed helped these dinosaurs not only in hunting, but also in fleeing danger such as “bigger theropods that could see them as their prey.”

“Their capacity to run very quickly and their maneuvering abilities surely allowed them to chase prey very efficiently. And of course I wouldn’t like to be caught by this guy on a riverbank,” added study lead author Pablo Navarro-Lorbes, a doctoral student at the same university.

“There are several factors that dictate the running ability of a dinosaur,” Navarro-Lorbes explained. “One of them is size. Some paleontologists think that theropods with sizes between 100 and 1,000 kilograms (220-2,200 pounds) could have been some of the best dinosaur runners because of the relationship between their weight and muscular performance.” Another factor is the dinosaurs’ elongated legs, which was of crucial importance for allowing them reach such speeds.

Further research is needed to clarify the precise mechanics characterizing these theropods’ movements, as well as their relations with other animal species with which they shared their environment.

The study is published in the journal Nature Scientific Reports.

—

By Andrei Ionescu, Earth.com Staff Writer