A forgotten fossil reveals a fearsome dinosaur with giant claws

The discovery was made by researchers led by University College London (UCL), who examined a fossil skull fragment originally found on the Isle of Wight. Their findings, published in the journal Royal Society Open Science, identify the dinosaur as Invictibellatrix amberina, the first known European member of a mysterious group of carnivorous dinosaurs called megaraptorans.

These agile predators walked on two legs and were closely related to tyrannosaurs, including the famous Tyrannosaurus rex. However, their hunting equipment was strikingly different. Rather than relying primarily on massive jaws, megaraptorans had relatively narrow skulls, powerful arms, and huge curved claws that helped them seize their prey.

Some members of this group eventually became enormous predators, rivaling tyrannosaurs in size. Invictibellatrix, however, was among the earliest and smallest megaraptorans discovered so far.

Its name translates to "unconquered female warrior," a reference to the powerful predators that later emerged from this evolutionary lineage.

A Forgotten Dinosaur That Could Have Hunted Humans

The fossil consists of part of the rear of the dinosaur's skull. Although the Natural History Museum acquired it in 1924, its scientific importance went unrecognized for generations.

By comparing the fragment with fossils from related dinosaurs, researchers were able to estimate what this long-extinct animal might have looked like and how it lived.

Lead author Dr. Cassius Morrison (UCL Earth Sciences) said: "Based on what we know about its closest relatives, Invictibellatrix would have been three to four meters long and just over a meter and a half in height -- about as tall as a human. It would likely have had feathers and its claws might have been about 10cm to 20cm long. It would have eaten small dinosaurs, lizards and mammals -- occupying a similar role in the food chain to the hyena today.

"It was not the apex predator of its time, but for humans this dinosaur would have been more dangerous than a T. rex. We would have been perfectly sized prey, about a third of their body weight. They definitely would have chased us. A T. rex would not have bothered, as we would have been too small.

"It is a real mystery that this fossil was overlooked for so long, sitting in a drawer for nearly 100 years. Lots of bones are found on the Isle of Wight -- who knows what else is waiting to be discovered."

Although humans never encountered these dinosaurs, Morrison's comparison highlights an intriguing difference between predators of different sizes. A relatively small carnivore might have regarded a human as worthwhile prey, whereas an enormous hunter such as T. rex may have preferred much larger animals.

Discovery Solves a Mystery About Dinosaur Evolution

Beyond identifying a previously unknown species, the fossil provides an important missing piece in the evolutionary history of megaraptorans.

These dinosaurs remain among the least understood groups of large meat eaters because their fossils are exceptionally rare. Scientists have long suspected that they first evolved in Asia before spreading through Europe and eventually reaching the southern supercontinent of Gondwana (including present-day Africa, South America and Antarctica).

There was one major problem with that explanation: Until now, no megaraptoran fossils had been identified in Europe.

The discovery of Invictibellatrix provides the evidence researchers needed to support that proposed migration route.

Co-author Charlie Scherer, a PhD student at UCL Earth Sciences, said: "This new species is the first proof we have that megaraptorans were also present in Europe and that they reached Gondwana this way rather than island-hopping further south."

The finding suggests that Europe was an important part of the journey that eventually brought these predators to the southern continents, where some of their descendants became dominant hunters.

CT Scans Reveal the Dinosaur's Hidden Anatomy

To determine exactly what kind of dinosaur they were examining, the scientists used CT scanning technology to investigate the fossil in detail.

The scans allowed them to build a three-dimensional reconstruction of the skull fragment, along with a model of its internal cavity. This provided clues about the shape of the space that once housed the dinosaur's brain.

The team then compared its anatomy with fossils from several other groups of meat-eating dinosaurs, including tyrannosaurs, spinosaurs, raptors, and other predators that walked on two legs.

Several unusual features helped distinguish the specimen from known species. These included an oval opening where the spinal cord connected to the brain and a distinctive crest shaped like an hourglass.

Together, these anatomical characteristics indicated that the fossil represented a previously unidentified dinosaur.

The researchers also used computer algorithms to compare its skeletal features with those of other dinosaurs. These analyses consistently placed Invictibellatrix within the megaraptoran group, providing further support for the identification.

How Giant Megaraptors Conquered the Southern Continents

The team went beyond examining the fossil itself, using mathematical models to reconstruct how megaraptorans spread and evolved over millions of years.

Their analysis combined the available fossil record with evolutionary relationships among dinosaurs, ancient geography, and climate conditions.

The results suggest that megaraptorans were distributed widely around the world during the Early Cretaceous (i.e., at the time of Invictibellatrix).

However, their fortunes appear to have changed dramatically as the Cretaceous continued.

By the Late Cretaceous, tens of millions of years later, megaraptorans had probably disappeared from the northern supercontinent of Laurasia (including modern-day Europe).

In the south, the story was very different. Megaraptorans continued evolving across Gondwana, eventually becoming some of the largest and most formidable predators in their ecosystems.

Some developed claws measuring up to 35cm (14") long. One particularly impressive example, Maip macrothorax, lived in what is now Argentina and is estimated to have reached nine to 10 meters in length, with a body weight comparable to that of an elephant.

Exactly why megaraptorans apparently vanished from northern regions remains uncertain. The researchers suggest several possibilities, including changes in climate, shifts in environmental conditions, and competition from other large carnivorous dinosaurs such as tyrannosaurs.

A Century-Old Museum Fossil Finally Reveals Its Secret

The fossil that made this discovery possible was originally collected by amateur paleontologist Reginald Walter Tooley near the base of a cliff on the southwestern coast of the Isle of Wight.

Tooley discovered more than 1,000 fossil specimens during his lifetime. Following his death, the Natural History Museum acquired his collection, including the skull fragment that would eventually be identified as Invictibellatrix.

The discovery highlights how important fossils can remain unrecognized even after spending decades in museum collections.

Professor Paul Barrett, the study's senior author from the Natural History Museum, said: "Despite over 200 years of collecting, the Isle of Wight continues to surprise us with new dinosaur species, and finds of carnivorous dinosaurs, such as Invictibellatrix, have been particularly elusive.

"Work like this shows the exceptional value of working with historical museum collections where there are still many discoveries to be made."

The researchers also gave the dinosaur's name a deeper meaning.

In their paper, they explained that Invictibellatrix was chosen to "give hope and strength to all those who are bullied, discriminated, victimized, and oppressed that tomorrow will be theirs and not to give up in face of such odds."

The second part of its name, amberina, honors both the amber found in the rock layers where the fossil originated and the female name Amberina.

The study received funding from the Palaeontographical Society, the Royal Society, and UKRI.

With a single forgotten skull fragment revealing an entirely new dinosaur and helping reconstruct the ancient movements of giant predators, the findings demonstrate that some of paleontology's most intriguing discoveries may already be sitting in museum drawers, waiting for someone to take a closer look.