London – June 26, 2025: A labrador-sized dinosaur misidentified for decades has been reclassified as a brand-new species, marking the first new dinosaur to be exhibited at London’s Natural History Museum in over a decade.
Named Enigmacursor mollyborthwickae—meaning “puzzling runner”—the dinosaur once thought to be a Nanosaurus was found to be something altogether unique.
This revelation is not only a triumph for palaeontology but also a fascinating glimpse into the evolutionary story of how small dinosaurs evolved into some of the most iconic giants of the prehistoric world.
Discovered in the renowned Morrison Formation of the western United States, Enigmacursor lived around 150 million years ago, during the Late Jurassic period, sprinting among massive contemporaries such as Stegosaurus.
Despite its comparatively diminutive size—standing 64 cm tall and stretching 1.8 metres long—it is now considered one of the most complete and significant skeletons of a small early dinosaur ever found.
Long Misidentified
For years, the specimen had been stored at the Natural History Museum (NHM) under the classification of Nanosaurus, a label historically applied to many small, bipedal dinosaurs discovered since the 19th century. But doubts lingered.
“When the dinosaur was donated to the museum, it was assumed to be Nanosaurus,” explained Professor Susannah Maidment, palaeontologist at NHM. “But we suspected it might not be that simple.”
That suspicion led to a rigorous investigation. Scientists from the NHM carried scans and photographs of the London specimen to the United States to compare it with the original Nanosaurus type specimen—only to find that the latter was not a full skeleton but merely a rock bearing some faint impressions of bone.
“It could be any number of dinosaurs,” Maidment remarked, underscoring the limitations of early fossil classification. In contrast, the NHM’s dinosaur was well-preserved, boasting nearly an entire skeleton with distinctive features, especially in its leg bones, that clearly set it apart from previously known species.
A Star Display After a Decade
On Thursday, Enigmacursor will make its public debut as the first new dinosaur to be displayed at NHM since 2014. It will be installed on a balcony overlooking the museum’s Earth Hall, sharing the space with another resident of the Morrison Formation—Sophie the Stegosaurus.
The unveiling has required meticulous preparation. Conservators Lu Allington-Jones and Kieran Miles were tasked with assembling the fragile remains onto a specially designed metal frame within a custom glass case.
“I don’t want to damage it at this stage before it’s revealed to everybody,” said Allington-Jones, NHM’s head of conservation.
Miles pointed out the physical features that define Enigmacursor’s athleticism. “The solid dense hips tell us it was built for speed. But look at the front limbs—they’re tiny and held off the ground. It may have used them to shovel plants into its mouth,” he said.
Despite its running capabilities, Enigmacursor likely wasn’t a very bright dinosaur. “It had a relatively small head, so it probably wasn’t the brightest,” noted Professor Maidment, who also confirmed the specimen was likely an adolescent when it died.
Filling Gaps in Dinosaur Evolution
The naming of Enigmacursor mollyborthwickae—the species named in honour of Molly Borthwick, a supporter of palaeontological research—is more than a case of scientific correction. It has wide-reaching implications for how scientists understand dinosaur evolution and diversity during the Late Jurassic.
“Specimens like this help fill in some of those gaps in our knowledge, showing us how those changes occurred gradually over time,” said Professor Paul Barrett, a fellow palaeontologist at the NHM.
“Smaller dinosaurs like this one are very close to the origins of the large groups of dinosaurs that later became very prominent—and often bizarre.”
The leg bones in particular were critical to the reclassification. “When we’re trying to identify a new species, we’re looking for minute differences in bone structures,” said Maidment. “In Enigmacursor, the leg morphology just didn’t match any known species.”
The scientists also used the opportunity to erase the Nanosaurus classification from scientific literature. “It’s foundational to our work to understand how many species we actually have. If we’ve got that wrong, everything else falls apart,” added Maidment.
The complete findings have been published in the journal Royal Society Open Science, alongside detailed illustrations and descriptions of the new dinosaur.
A Spotlight on Small Dinosaurs
The discovery is a timely reminder that while massive, headline-grabbing fossils tend to dominate public and academic attention, smaller species are crucial to understanding the full ecological picture of the prehistoric world.
“When you’re looking for those very big dinosaurs, sometimes it’s easy to overlook the smaller ones living alongside them,” said Barrett. “But now I hope people will keep their eyes close to the ground, looking for these little ones.”
Smaller dinosaurs often lived in the shadows of their larger counterparts—literally and figuratively. Yet, as Enigmacursor demonstrates, they hold key insights into evolutionary pressures and adaptations.
These creatures likely gave rise to later, more dramatic evolutionary branches that included horned, armoured, and crested dinosaurs.
A New Era of Classification
The story of Enigmacursor highlights how palaeontology is increasingly reliant on international collaboration, digital imaging, and meticulous comparative anatomy. By travelling across continents and revisiting historical records with modern tools, today’s scientists are rewriting the narrative of life on Earth.
For museum visitors, Enigmacursor offers not only a glimpse into a lost world but also a testament to the ever-evolving nature of science itself. Its elegant display, beside its Jurassic cousin Stegosaurus, is a reminder that even the smallest dinosaurs can make the biggest impact.
As conservationist Kieran Miles puts it: “Every bone tells a story. We’re just now learning how to listen more carefully.”
