Isle of Wight skull fossil named as new European megaraptoran dinosaur

A fossil fragment collected on the Isle of Wight decades ago has been identified as a new dinosaur species belonging to a group of clawed predators never before confirmed in Europe, the Natural History Museum (NHM) in London announced.

The species has been named Invictibellatrix amberina. It is described in a study published in the journal Royal Society Open Science by a team led by the University College London (UCL).

How the fossil was found and studied

The specimen is a partial braincase, the back portion of the skull. According to the Natural History Museum and Phys.org, it was originally found at the foot of a cliff on the south-west coast of the Isle of Wight by amateur palaeontologist Reginald Walter Tooley, and it was acquired by the museum in 1924, after Tooley's death.

The museum says the fossil sat unstudied for close to a century before the research team examined it. Scientists used CT scanning to build three-dimensional models of the skull and the cavity that once held the animal's brain.

The study was led by Dr Cassius Morrison of UCL Earth Sciences, with Charlie Scherer, a PhD student at UCL, as a co-author, and Professor Paul Barrett of the Natural History Museum as senior author.

What the fossil reveals about the animal

The rocks the fossil came from date to the Early Cretaceous period, about 120 million years ago, according to the Natural History Museum. Based on comparisons with closely related species, researchers estimate Invictibellatrix amberina was three to four metres long and just over a metre and a half tall, roughly the height of a human, and may have been covered in filament-like feathers.

The skull shows an oval opening where the spinal cord entered the brain and a distinctive hourglass-shaped crest, features the researchers used to distinguish it as a new species, the museum said.

Invictibellatrix amberina is classified as a megaraptoran, a group of agile, two-legged carnivorous theropods related to tyrannosaurs but with comparatively slender skulls. Unlike tyrannosaurs, which relied mainly on powerful jaws, megaraptorans are thought to have used large curved hand claws, estimated at roughly 10 to 20 centimetres long, as a primary weapon against prey.

Morrison's point, as reported by the museum, is that a human-sized animal would have been within the prey range of Invictibellatrix amberina, whereas an adult Tyrannosaurus rex is generally considered to have hunted much larger animals.

Why the discovery matters

Before this find, megaraptorans were known mainly from fossils in Asia, Australia and South America, where some later members of the group grew far larger. The Isle of Wight specimen is described by the research team as the first confirmed megaraptoran body fossil from Europe, which they say supports the idea that the group may have dispersed from Asia through Europe before reaching southern continents.

The genus name Invictibellatrix means "unconquered female warrior," while the species name amberina refers to amber found in the rock layer where the fossil was recovered, according to the study's description reported by the museum and by Phys.org.