New Dog-Sized Dinosaur Had Quite the Tail

Hidden among the giants of the Jurassic era, a dog-sized dinosaur has been uncovered as a new species, rewriting what scientists thought they knew about these ancient ecosystems. Enigmacursor mollyborthwickae, meaning "puzzling runner," now on display at London's Natural History Museum (NHM), offers rare insight into the small but significant creatures that once thrived in the shadows of dinosaurs like Stegosaurus. Researchers at NHM established that Enigmacursor—previously misclassified as Nanosaurus, a category of dinosaur now formally erased—actually represents a distinct species, per the BBC.

The two-legged herbivore, described in Royal Society Open Science, lived around 150 million years ago and coexisted with much larger dinosaurs such as Stegosaurus in what is now the Western United States. The species was about the size of a Labrador, but with much larger feet and a tail "probably longer than the rest of the dinosaur," NHM palaeontologist Susannah Maidment tells the BBC. The nearly complete skeleton of a presumed teenage Enigmacursor, excavated at a commercial quarry in 2021-22, offers rare insight into the anatomy and lifestyle of small dinosaurs, with features suggesting it ran quickly, per a release. "It also had a relatively small head, so it was probably not the brightest," says Maidment.