It is a 113-million-year-old bone of contention.

After Stuttgart’s museum of natural history bought a fossilised dinosaur skull in 1991, researchers found it was the most complete spinosaurid skull known to date, belonging to a previously unknown genus of the huge meat-eating dinosaurs.

Palaeontologists studying the skull in 1996 dubbed the genus Irritator – reflecting the annoyance they felt when they discovered the snout had been tinkered with – and the particular species challengeri , after Professor Challenger from Arthur Conan Doyle’s dinosaur adventure novel, The Lost World.

But as study after study was published, other interested parties were watching with irritations of their own: experts in Brazil , where the skull is believed to have originated.

According to a Brazilian law passed in 1942, fossils found in the country belong to the state , and, since 1990, specimens can be exported only with a permit and a partnership with a Brazilian scientific institution.

No one knows exactly when Irritator…