Long-Clawed Dinosaur Rediscovered in Natural History Museum Is Britain's First Megaraptoran

In 2020, Paul Barrett, a palaeontologist at the Natural History Museum in London, was looking through the fossil collections when he picked out a small chunk of bone. He recognised it as the braincase, an important part of a dinosaur skull. Museum records showed it had been found on a beach near Sudmoor Point on the Isle of Wight, the island off England's south coast known for its dinosaur fossils. It had been in storage for more than a century.

The museum holds over 30 million specimens and is nearly 150 years old, so the authors of the new study say it is easy to see how one fossil could be forgotten. Knowing the bone came from the Isle of Wight, Barrett asked Cassius Morrison, then a PhD student specialising in dinosaur braincases, to study it in detail and work out what animal it belonged to.

The answer was unexpected. The roughly 120 million year old fossil was unlike anything previously found on the island. It belonged to a new species in the Megaraptora, a family of carnivores that includes the long-clawed predators. The researchers named it Invictibellatrix amberina. The name translates to "unconquered [female] warrior of the amber" and honours the role megaraptorans later played as apex predators in the late Cretaceous of South America.

Megaraptorans are known for slender skulls, lightly built skeletons and huge hand claws, which on some larger species exceed a foot in length. Most known species come from South America, particularly Argentina. Invictibellatrix was small by comparison: about 5 metres from head to tail and about as heavy as a large tiger, which makes it the smallest known megaraptoran.

To identify it, the team compared the braincase directly with the skulls of other carnivores, a kind of scientific spot-the-difference. They also used computed tomography (CT) scanning, which combines X-rays and computer processing, to look inside the braincase and study what they could of the brain. They then fed their findings into a computer algorithm to place the species on the family tree, a step meant to limit bias in their interpretations.

The results suggest Invictibellatrix belongs to the early days of megaraptoran evolution, showing what these animals looked like before they grew very large, as their relatives the tyrannosaurs also did. That matters because of how thin the record was. Before this find, megaraptorans were known only from early Cretaceous species (130 to 120 million years ago) in Thailand and Japan, and from several larger late Cretaceous species (85 to 66 million years ago) in Australia and Argentina.

The authors argue that, because large animals could not swim the oceans separating the continents, megaraptorans must have been more widespread than their fossils show. As the first European megaraptoran, Invictibellatrix is strong evidence, they say, that the group travelled to the southern continents from Asia via Europe and Africa, then spread across South America and Australia during or perhaps before the early Cretaceous. It also implies that other megaraptorans may be waiting to be found in Africa and even Antarctica.

On the Isle of Wight it probably shared its world with other carnivores: Neovenator, a relative of Allosaurus; Ceratosuchops, a relative of Spinosaurus; and Eotyrannus, an early relative of Tyrannosaurus rex. They likely hunted different prey. The spinosaur specialised in fish, while the others took land animals. Invictibellatrix probably fed on small dinosaurs, mammals, lizards and even crocodiles.

The fossil does not settle everything. Scientists still do not know when megaraptorans first evolved, though this braincase offers clues. The authors point to the museum shelves as a place where more answers may be waiting.