Why a century-old taxonomic tangle finally revealed a new dinosaur species
In short: For decades, paleontologists overlooked small herbivores in the famous Morrison Formation, favoring the giants. A recent discovery, Enigmacursor mollyborthwickae, proves that even well-studied regions hide secrets. By re-examining fossils once dismissed as poorly preserved, scientists are correcting historic assumptions and uncovering a hidden world of speedy, small-bodied dinosaurs.
The Morrison Formation in the western United States is world-renowned for iconic dinosaurs like Allosaurus and Stegosaurus. However, its smaller inhabitants have long been ignored by researchers focused on the largest, most impressive specimens. This bias created a 'taxonomic tangle' that persisted for over a century, leaving many smaller species misidentified or forgotten in the ground. The recent naming of Enigmacursor mollyborthwickae, a small herbivore from the Late Jurassic period, serves as a correction to this historical oversight.
Enigmacursor, meaning 'mysterious runner,' lived between 152 and 145 million years ago. Roughly one metre long, this dinosaur possessed long legs that likely allowed it to dart away from predators like Ceratosaurus. Researchers Susannah Maidment and Paul Barrett identified the specimen after it was unearthed on private land between 2021 and 2022. Initially marketed as Nanosaurus—a poorly defined species named in 1877—the fossils underwent rigorous analysis at the Natural History Museum in London. The team discovered that the original Nanosaurus classification relied on impressions in hardened sand that were insufficient for modern scientific standards.
The study of Enigmacursor highlights how much paleontological methods have evolved since the 19th century. By examining neural arches in the vertebrae, experts suggest the specimen was likely still growing, though previous preparation of the fossil makes this difficult to confirm. This discovery is significant not just for the animal itself, but for what it represents: a shift in focus toward the smaller, often-overlooked dinosaurs that populated ancient riverbanks. Experts believe this is likely the first of many such discoveries to emerge from the Morrison Formation, proving that even in well-studied regions, the history of life on Earth is far from fully written.
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Sources
- Summary by Intellect · source: Five new species of dinosaur discovered in 2021 | Natural History Museum
- Also: New species of ‘mystery’ dinosaur unveiled at the Natural History Museum | Natural History Museum
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