Enigmacursor mollyborthwickae, the newcomer at the Natural History Museum © Trustees of the Natural History Museum

Museum experts have carried out critical scientific research on the specimen, settling a century-long taxonomic tangle and defining this fossil as a new species to science.

A new species of dinosaur, Enigmacursor mollyborthwickae, a two-legged herbivore from the famous Morrison Formation in the USA, has been officially recognised by science – and from Thursday 26 June is on display at the home of dinosaurs, the Natural History Museum, for visitors to meet.

Wind the clock back 145 to 150 million years, and Enigmacursor mollyborthwickae, standing at half a metre tall and a little over a metre long, would have been darting around the floodplains of the western United States in the shadows of giants like Diplodocus (such as Dippy) and Stegosaurus (like Sophie, who also resides in the Museum’s Earth Hall).

There are signs that the dinosaur was not fully grown: the top section of vertebrae (the neural arches), which form separately to the lower parts and fuse together as the animal ages, were not fully fused in place, suggesting Enigmacursor may have been quite young.

It would also have been a speedy runner, hence the latter part of its genus name, ‘cursor’. ‘Enigma’ relates to the mystery surrounding the taxonomic tangle that has been resolved today by new research published in the journal Royal Society Open Science (paper here), co-authored by Museum palaeontologists Prof. Susannah Maidment and Prof. Paul Barrett.

Prof. Susannah Maidment, co-lead author of the new study, comments: “The generous donation of this rare specimen has had quite unexpected scientific repercussions. By studying its anatomy in detail, we’ve been able to clarify this species’ evolutionary relationships, its taxonomy and the diversity of a previously poorly understood group of small dinosaurs."

“Getting taxonomy right is vital; it underpins everything we do as palaeontologists and if we get it wrong, everything else collapses. Rather than simply assigning fossils to familiar names, this discovery shows just how vital rigorous taxonomic work is – which requires us to get in front of and scrutinise new fossils – to inform our understanding of the evolution of these fascinating creatures."

Prof. Paul Barrett, co-lead author, adds: ‘‘Unveiling Enigmacursor mollyborthwickae in our world-class natural history museum, whilst also placing it reliably onto the evolutionary tree, is an incredibly exciting milestone. Enabling access to a high-quality specimen, made possible by donation, for our millions of visitors is an important part of our work to inspire an appreciation of the wonders of the natural world and its deep history.”

Unearthed back in 2021/2022 from a commercial quarry, Enigmacursor was acquired from the gallery David Aaron Ltd thanks to the support of David and Molly Lowell Borthwick.

At the time, it was thought to be a Nanosaurus – a poorly-known species of small herbivorous dinosaur first named in the 1870s. However, on closer inspection, Susie and Paul deemed the original Nanosaurus specimen too poorly preserved to serve as a reliable reference for identification.

With better-quality fossils having been found, they officially set aside the name Nanosaurus in the interest of taxonomic stability. Differences between the original specimen and the Museum’s new specimen were the final pieces of the puzzle to confirm it as a new genus and species.

More research is now needed to confirm whether other specimens around the world previously thought to be Nanosaurus are also different species, all of which once shared the Morrison landscape with Enigmacursor.

Enigmacursor mollyborthwickae will be on permanent public display on the first-floor mezzanine in Earth Hall from Thursday 26th June 2025.

With thanks to the support of David and Molly Lowell Borthwick.

Along with the planned gallery redevelopments ahead of the Museum’s 150th anniversary, this awe-inspiring new display forms part of its commitment to showcase natural world treasures and create new advocates for the planet.

Visitors should book a free ticket in advance online for guaranteed entry to the Museum. Members, Patrons and Corporate Supporters do not need to book general admission or exhibition tickets. Arrive at any time and you will have priority access.

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Images are available here.

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