A partial dinosaur braincase that sat unstudied in the Natural History Museum in London for roughly a century has been identified as a new genus and species of predatory dinosaur, researchers report in Royal Society Open Science. The animal, named Invictibellatrix amberina, was a megaraptoran theropod distantly related to Tyrannosaurus rex and is the first member of that group ever found in Europe.
The fossil was acquired by the museum from Reverend Reginald Hooley in 1924, two years after it was collected from 120-million-year-old rocks of the Lower Cretaceous Wessex Formation on the south-west coast of the Isle of Wight. «It was sitting unstudied in the museum for about 100 years, which is very surreal,» said Cassius Morrison, now at the University of Leeds, who led the work.
Morrison and his colleagues used CT scans to build a three-dimensional model of the braincase and compared its anatomy with that of other dinosaurs. The closest match was Murusraptor, an Argentinian megaraptoran that lived about 80 million years ago. On that basis, the team concludes the Isle of Wight specimen belongs to a previously unknown species within Megaraptora, a group of carnivorous dinosaurs otherwise known from Asia, Australia and South America.
The genus name Invictibellatrix translates as «unconquered female warrior.» The researchers estimate the animal was an agile, two-legged carnivore about 3 to 4 metres long, roughly 1.5 metres tall and weighing between 200 and 300 kilograms. Morrison says it likely bore feathers and carried claws 10 to 20 centimetres long, used to attack small dinosaurs, lizards and mammals. «Had we been around then, humans would have been perfect-sized prey, about a third of their body weight,» he said.
At the time Invictibellatrix lived, the Isle of Wight was still firmly attached to mainland Britain and the rest of Europe, and the local environment was subtropical. A similar-looking dinosaur, the 5-metre-long Eotyrannus, is known from a few million years earlier in the same formation. But the two specimens do not overlap in the bones preserved, making direct comparison difficult, and Eotyrannus has previously been considered a possible megaraptoran relative.
Morrison proposes that Invictibellatrix descended from Asian megaraptorans that dispersed into Europe around 130 million years ago. Megaraptorans then spread from Europe to Africa and onward to South America and Australia before the continents fully separated. A European megaraptoran would help connect those scattered fossil records into a single narrative.
Jake Kotevski of Monash University in Melbourne called the limited comparison with Eotyrannus unfortunate. «If Invictibellatrix is indeed a megaraptoran, it expands the palaeobiogeographic range of the group and plugs a significant gap in our knowledge, linking those from South-East Asia to Australia and South America via Europe and Africa,» he said. «However, more fossils are required to support or reject this hypothesis.»
The finding adds to the growing picture of Early Cretaceous ecosystems on the Isle of Wight, where the Wessex Formation has yielded a diverse assemblage of dinosaurs and other vertebrates. For now, the century-old braincase stands as the first European evidence of a group whose evolutionary history spanned multiple continents.