Isle of Wight fossil Europe's first known long-clawed megaraptoran dinosaur

A new species of dinosaur—a long-clawed predator the size of a large tiger—has been discovered by a UCL-led team from a fossil found on the Isle of Wight. The dinosaur, described in a new paper in the journal Royal Society Open Science, belongs to a group of agile, two-legged carnivores called megaraptorans and is the first of this group to be found in Europe.

Megaraptorans were closely related to tyrannosaurs including Tyrannosaurus rex but had slender heads, attacking prey with their large arms and giant curved claws instead of their jaws.

While some species grew to gigantic sizes, just as tyrannosaurs did, this new species is one of the smallest and earliest of the group to be found, living in the U.K. in the Early Cretaceous period about 120 million years ago.

It has been named Invictibellatrix amberina. Invictibellatrix means "unconquered female warrior"—honoring megaraptorans' future role as massive apex predators.

The fossil, a chunk of the back of a skull, was acquired by the Natural History Museum in 1924 and had been overlooked for study until now.

A human-sized hunter with giant claws

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 (10 to 13 feet) long and just over a meter and a half (5 feet) in height—about as tall as a human. It would likely have had feathers and its claws might have been about 10cm to 20cm (4 to 8 inches) 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."

Evidence for a migration route through Europe

Megaraptors are regarded as the most mysterious of the large, meat-eating dinosaurs, as few megaraptor fossils have been found.

They are thought to have originated in Asia, before migrating through Europe and becoming apex predators throughout the southern landmass of Gondwana (including present-day Africa, South America and Antarctica).

But until now, this theory was missing key fossil evidence, as no megaraptorans had been found in Europe.

Co-author Charlie Scherer, a Ph.D. 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."

Skull features reveal a distinct species

For the study, researchers undertook a CT scan of the fossil, creating a 3D model of this part of the skull as well as a model of the interior of the skull, i.e., the brain.

The researchers compared the fossil with skulls and brain cases from tyrannosaurs, spinosaurs, raptors and other two-legged meat-eating dinosaurs.

A unique combination of skull features, including an oval hole where the spinal cord entered the brain and an hourglass-shaped crest, led researchers to conclude it was a new species.

Computer algorithms analyzing how the traits of the skull fit in with those of other species consistently found the specimen belonged to the megaraptoran family.

Southern dominance and northern decline

The research team also used mathematical modeling to investigate how the spread of megaraptors around the world might have changed over time, based on fossils discovered so far, dinosaurs' evolutionary trees, geography and climate.

The team concluded that megaraptors were globally widespread in the Early Cretaceous (i.e., at the time of Invictibellatrix), but by the Late Cretaceous tens of millions of years later they had likely become extinct in the giant northern landmass of Laurasia (including modern-day Europe).

During this later period, megaraptors became apex predators throughout Gondwana in the south, reaching gigantic sizes, with claws up to 35cm (14in) long.

The study did not explain why megaraptors likely died out in the north, but this may have been a result of shifts in climate or environment, or the presence of competing predators such as other tyrannosaurs.

Discoveries still waiting in museum collections

The Invictibellatrix fossil was originally found at the foot of a cliff on the southwest coast of the Isle of Wight by amateur paleontologist Reginald Walter Tooley. It was one of more than 1,000 specimens discovered by Tooley that were acquired by the Natural History Museum after his death.

Professor Paul Barrett, the study's senior author from the Natural History Museum, adds, "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."

In the paper, the researchers said the name Invictibellatrix was intended to "give hope and strength to all those who are bullied, discriminated against, victimized and oppressed that tomorrow will be theirs and not to give up in the face of such odds." Amberina, meanwhile, refers to the amber found in the rocks where the fossil was discovered, as well as to the female name.