2025-06-26 06:00:54.634

Scientists have discovered a new species of dinosaur—a dog-sized herbivore that roamed what is now the United States around 150 million years ago. The Enigmacursor mollyborthwickae, named in a study published in the Royal Society Open Science, was about the size of a Labrador Retriever, with a tail making up half its length. While many bones were unearthed from the Morrison Formation in Colorado, its skull and parts of its vertebral column were missing, leaving its precise length uncertain. Professor Paul Barrett of the Natural History Museum, who co-led the study, noted the rarity of finding complete skeletons of these small plant-eating dinosaurs. The skeleton, described as "lightly built" and weighing about as much as a Collie, will be displayed at the Natural History Museum from June 26. Its long hind legs suggest it was a fast runner, allowing it to escape predators. The species name honors donor Molly Borthwick, while the genus name, "Enigmacursor," means "mysterious runner." Its thigh bone has unique muscle attachments, distinguishing it from other known species. Closely related to the Chinese Yandusaurus hongheenis, its wide distribution is hypothesized. While some vertebrae were unfused, suggesting it wasn't fully grown, the cause of death is unclear. The discovery highlights the rarity of finding small dinosaurs, often overlooked or destroyed by scavengers, but adds valuable information about ancient ecosystems.