A tiny yet swift-footed dinosaur from the Jurassic era has fascinated scientists and significantly enhanced our understanding of small plant-eating dinosaurs. Named Enigmacursor mollyborthwickae, this cat-sized runner from Colorado’s Morrison Formation offers valuable insights into dinosaur evolution, behaviour, and ecology. Measuring just about three feet long, it was a fast, agile herbivore that relied on speed to survive among giants. Now proudly displayed at London’s Natural History Museum, the remarkably preserved fossil sheds light on an often-overlooked group of nimble, two-legged plant-eaters. Its discovery helps scientists piece together the complex web of life that once thrived on the Jurassic floodplains over 150 million years ago.
New species Enigmacursor mollyborthwickae shows how small dinosaurs survived
Measuring just about three feet long, Enigmacursor mollyborthwickae may have been small in size, but it represents a major discovery in palaeontology. Unearthed on private land in Colorado between 2021 and 2022, this fossil has since travelled thousands of miles to the UK, where researchers have meticulously analysed its bones. According to lead researcher Susannah Maidment of the Natural History Museum, London, the dinosaur’s name tells part of its story: the genus name Enigmacursor combines “enigma” for its mysterious identity and “cursor,” meaning “runner,” a nod to its swift, long‑legged form. Moreover, a study published in Royal Society Open Science (2025) confirmed that the proportions of its femur, tibia, and ankle structure indicate it was a fast, agile creature perfectly adapted for life on open floodplains, where speed would have been its best defence.
Scientists use a new fossil to redefine small dinosaurs of the Morrison Formation
For over a century, small plant-eating dinosaurs from the Morrison Formation, a vast rock unit spanning the western United States, were often grouped under broad, outdated names like Nanosaurus.
However, a comprehensive 2025 review by palaeontologists Paul Barrett and Susannah Maidment determined that many of these old names were nomina dubia, labels based on incomplete fossils too fragmentary to classify accurately.
Enigmacursor mollyborthwickae provides a crucial turning point. It serves as a holotype, a complete, well-documented reference specimen that defines the species. With its hips, legs, arms, and spine preserved from a single individual, it offers scientists a reliable framework for comparing similar fossils in the future.
When its anatomical features were analysed and scored, Enigmacursor appeared most closely related to Yandusaurus, a small Jurassic dinosaur from China, suggesting a broader global connection among early bird-hipped herbivores known as neornithischians.
What the Morrison Formation reveals about small dinosaurs like Enigmacursor
The Morrison Formation, which dates back around 150 million years, is famous for yielding fossils of gigantic dinosaurs like Apatosaurus, Stegosaurus, and Allosaurus. But among these giants also lived small, fast herbivores like Enigmacursor, darting through the vegetation and feeding on low-growing plants.
For such a small creature, roughly knee-high to a human, life in the shadow of predators and colossal sauropods would have been perilous. Agility, alertness, and quick reflexes were likely its best means of survival.
This discovery paints a more dynamic picture of Jurassic ecosystems. Instead of a world dominated solely by the massive and the mighty, it highlights a thriving community of small, active herbivores that helped sustain the balance of prehistoric environments.
How 3D scanning Enigmacursor mollyborthwickae is revolutionising dinosaur research
What makes Enigmacursor mollyborthwickae even more remarkable is not just its anatomy but how it’s being studied. The fossil was 3D scanned in high detail, allowing researchers worldwide to examine it digitally without risking damage to the original bones.
These digital replicas capture features finer than a millimetre, including muscle attachment marks, bone texture, and growth lines. The scans are now part of open-access datasets, ensuring that scientists across disciplines, from biomechanics to evolutionary biology, can study and compare this specimen freely.
Professor Maidment emphasised that digitisation is transforming modern palaeontology:
“Smaller dinosaurs are often left behind, meaning there are probably many still in the ground. But with digital models, even fragile specimens can become accessible to everyone.”
By turning rare fossils into virtual assets, researchers are accelerating the pace of discovery, verifying old classifications, and preserving delicate finds for future generations.
Small dinosaur discovery reveals new clues about Jurassic evolution
Small dinosaurs like Enigmacursor rarely make headlines, partly because their bones are fragile and often missed during excavation, and partly because collectors have historically focused on larger, more dramatic fossils.
Yet, this discovery is rewriting that narrative. The recognition and proper classification of small dinosaurs help scientists understand how many species truly lived during the Jurassic period and how they interacted within ecosystems.
It also strengthens the evolutionary placement of Yandusaurus and related neornithischians, supporting the idea that the Morrison Formation hosted a greater diversity of small plant-eaters than previously recognised.
Ultimately, Enigmacursor mollyborthwickae is more than just a new name on the dinosaur family tree; it’s a key piece in understanding how speed, agility, and small-body adaptation evolved in an age dominated by giants.
Scientists say Enigmacursor bridges millions of years of evolution
The story of Enigmacursor bridges past and present, from its fossilised bones, buried for millions of years, to its digital scans, accessible in modern research databases.
This “enigmatic runner” reminds us that evolution’s most fascinating experiments weren’t always the biggest or most famous creatures, but sometimes the smallest, those that relied on agility and intelligence to thrive in a dangerous world.
As palaeontologists continue to revisit old collections and explore new sites, they believe many more small dinosaurs remain undiscovered, waiting to add their chapters to Earth’s ancient story.
Also read | The deadly lake that turns animals to stone: Unravelling the mystery of Lake Natron’s red glow
New species Enigmacursor mollyborthwickae shows how small dinosaurs survived
Measuring just about three feet long, Enigmacursor mollyborthwickae may have been small in size, but it represents a major discovery in palaeontology. Unearthed on private land in Colorado between 2021 and 2022, this fossil has since travelled thousands of miles to the UK, where researchers have meticulously analysed its bones. According to lead researcher Susannah Maidment of the Natural History Museum, London, the dinosaur’s name tells part of its story: the genus name Enigmacursor combines “enigma” for its mysterious identity and “cursor,” meaning “runner,” a nod to its swift, long‑legged form. Moreover, a study published in Royal Society Open Science (2025) confirmed that the proportions of its femur, tibia, and ankle structure indicate it was a fast, agile creature perfectly adapted for life on open floodplains, where speed would have been its best defence.
Scientists use a new fossil to redefine small dinosaurs of the Morrison Formation
For over a century, small plant-eating dinosaurs from the Morrison Formation, a vast rock unit spanning the western United States, were often grouped under broad, outdated names like Nanosaurus.
However, a comprehensive 2025 review by palaeontologists Paul Barrett and Susannah Maidment determined that many of these old names were nomina dubia, labels based on incomplete fossils too fragmentary to classify accurately.
Enigmacursor mollyborthwickae provides a crucial turning point. It serves as a holotype, a complete, well-documented reference specimen that defines the species. With its hips, legs, arms, and spine preserved from a single individual, it offers scientists a reliable framework for comparing similar fossils in the future.
When its anatomical features were analysed and scored, Enigmacursor appeared most closely related to Yandusaurus, a small Jurassic dinosaur from China, suggesting a broader global connection among early bird-hipped herbivores known as neornithischians.
What the Morrison Formation reveals about small dinosaurs like Enigmacursor
The Morrison Formation, which dates back around 150 million years, is famous for yielding fossils of gigantic dinosaurs like Apatosaurus, Stegosaurus, and Allosaurus. But among these giants also lived small, fast herbivores like Enigmacursor, darting through the vegetation and feeding on low-growing plants.
For such a small creature, roughly knee-high to a human, life in the shadow of predators and colossal sauropods would have been perilous. Agility, alertness, and quick reflexes were likely its best means of survival.
This discovery paints a more dynamic picture of Jurassic ecosystems. Instead of a world dominated solely by the massive and the mighty, it highlights a thriving community of small, active herbivores that helped sustain the balance of prehistoric environments.
How 3D scanning Enigmacursor mollyborthwickae is revolutionising dinosaur research
What makes Enigmacursor mollyborthwickae even more remarkable is not just its anatomy but how it’s being studied. The fossil was 3D scanned in high detail, allowing researchers worldwide to examine it digitally without risking damage to the original bones.
These digital replicas capture features finer than a millimetre, including muscle attachment marks, bone texture, and growth lines. The scans are now part of open-access datasets, ensuring that scientists across disciplines, from biomechanics to evolutionary biology, can study and compare this specimen freely.
Professor Maidment emphasised that digitisation is transforming modern palaeontology:
“Smaller dinosaurs are often left behind, meaning there are probably many still in the ground. But with digital models, even fragile specimens can become accessible to everyone.”
By turning rare fossils into virtual assets, researchers are accelerating the pace of discovery, verifying old classifications, and preserving delicate finds for future generations.
Small dinosaur discovery reveals new clues about Jurassic evolution
Small dinosaurs like Enigmacursor rarely make headlines, partly because their bones are fragile and often missed during excavation, and partly because collectors have historically focused on larger, more dramatic fossils.
Yet, this discovery is rewriting that narrative. The recognition and proper classification of small dinosaurs help scientists understand how many species truly lived during the Jurassic period and how they interacted within ecosystems.
It also strengthens the evolutionary placement of Yandusaurus and related neornithischians, supporting the idea that the Morrison Formation hosted a greater diversity of small plant-eaters than previously recognised.
Ultimately, Enigmacursor mollyborthwickae is more than just a new name on the dinosaur family tree; it’s a key piece in understanding how speed, agility, and small-body adaptation evolved in an age dominated by giants.
Scientists say Enigmacursor bridges millions of years of evolution
The story of Enigmacursor bridges past and present, from its fossilised bones, buried for millions of years, to its digital scans, accessible in modern research databases.
This “enigmatic runner” reminds us that evolution’s most fascinating experiments weren’t always the biggest or most famous creatures, but sometimes the smallest, those that relied on agility and intelligence to thrive in a dangerous world.
As palaeontologists continue to revisit old collections and explore new sites, they believe many more small dinosaurs remain undiscovered, waiting to add their chapters to Earth’s ancient story.
Also read | The deadly lake that turns animals to stone: Unravelling the mystery of Lake Natron’s red glow
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