Dr Angela Milner compares the two dinosaurs
Scientists have identified the most ancient fossil relative of the dinosaur Tyrannosaurus rex.
The new addition to
T. rex's clan is known from a 30cm-long skull uncovered during excavations in Gloucestershire in the 1900s.
The well-preserved fossil is held in London's Natural History Museum.
A British-German team has now uncovered evidence linking it to what may be the most famous dinosaur family of all.
The dinosaur, named
Proceratosaurus, lived about 165m years ago, during the middle Jurassic Period.
The two-legged meat-eater would have measured about 3m long and weighed up to 60kg.
The palaeontologists used computed tomography (CT) techniques to generate a 3D image of the delicate skull to investigate its internal structure in meticulous detail.
Dr Angela Milner, associate keeper of palaeontology at the Natural History Museum, told BBC News: "This is a unique specimen. It is the only one of its kind known in the world."
She added: "It was quite a surprise when our analysis showed we had the oldest known relative of T. rex.
"Fossils collected a century ago can now be studied again with the benefit of much greater knowledge of dinosaurs from around the world."
Originally described in 1910 as a new species of
Megalosaurus, the fossil was presented to the museum in 1942.
The skull had been unearthed during excavations for a reservoir close to Minchinhampton in Gloucestershire.
T. rex lived during the Cretaceous Period
Dr Milner said that despite obvious differences between the skulls of
Proceratosaurus and T. rex - such as their divergent sizes - the two shared many similarities.
"If you look at the animal (
Proceratosaurus) in detail, it has the same kinds of windows in the side of the skull for increasing the jaw muscles," she told BBC News.
"It has the same kinds of teeth - particularly at the front of the jaws. They're small teeth and almost banana-shaped, which are just the kind of teeth
T. rex has."
"Inside the skull, which we were able to look at using CT scanning, there are lots of internal air spaces.
Tyrannosaurus had those as well."
Although the skull has attracted much interest because of its exquisite preservation, it has not been closely studied until now, thus, its link to the tyrannosaurs remained undiscovered.
"This is still one of the best-preserved dinosaur skulls found in Europe," said co-author Dr Oliver Rauhut from the Bavarian State Collection for Palaeontology and Geology in Munich.
"It is really surprising that it has received so little attention since its original description."