A new species of one of the most recognisable types of dinosaur is also the oldest of its kind ever discovered, British scientists believe.

Remains of a stegosaurus, an armoured dinosaur instantly recognisable by the plate-like bones protruding from its spine and spikes on its tails, were studied by a team from the Natural History Museum and belong to a new genus that walked the earth around 168m years ago.

Despite the specimen including only a few vertebrae and an upper-arm bone, scientists concluded it was a new species and genus which dates to the middle Jurassic period – much earlier than most known stegosaurs.

The team, led by Dr Susannah Maidment, named it Adratiklit boulahfa, meaning “mountain lizard” in the Berber language.

Boulahfa is a reference to the area in the Middle Atlas mountains of Morocco where the specimen was found.

“The discovery of Adratiklit boulahfa is particularly exciting as we have dated it to the middle Jurassic,” said Maidment.

“Most known stegosaurs date from far later in the Jurassic period, making this the oldest definite stegosaur described and helping to increase our understanding of the evolution of this group of dinosaurs.”

The specimen is the first stegosaur, a thyreophoran dinosaur, to be found in North Africa. Thyreophoran dinosaurs are found across much of the globe and have been mainly attributed to Laurasian rock formations, the team explained.

This has suggested that when the Earth was divided into two supercontinents, Laurasia and Gondwana, thyreophorans were more common and diverse in Laurasia. But the recent discovery could dispute that.

Maidment added: “Most stegosaurs we know of, including the Natural History Museum’s Sophie, the most complete stegosaur discovered, have been found in Laurasian rock formations.

“This, however, may not mean that stegosaurs were not so common in Gondwana and in fact may be due to the fact that Gondwana rock formations have been subject to far fewer excavations and detailed studies.”

The team said the discovery adds to the theory the Gondwanan fossil record of armoured dinosaurs is significantly biased by geological factors and collection efforts.

Maidment said: “What is exciting about this is that there could be many more thyreophoran dinosaurs to find in places that until now have not been excavated.”

Further discoveries in the region will provide an improved view of the distribution of this group of dinosaurs and could result in a more complete specimen of Adratiklit boulahfa, the team said.