The new species, dubbed Tyrannoneustes lythrodectikos or "blood-biting tyrant swimmer," belonged to a group of ancient crocodiles with dolphin-like features, they said.
The reptile's partial skeleton, including a jawbone and teeth, has been housed in the Hunterian Museum at the University of Glasgow since an amateur fossil hunter found it in a clay pit near Peterborough in England in the early 1900s.
Experts have only now been able to confirm the identity of the remains, The Scotsman reported Tuesday.
"It is satisfying to be able to classify a specimen that has been unexamined for more than 100 years, and doubly so to find that this discovery improves our understanding of the evolution of marine reptiles," University of Edinburgh researcher Mark Young said.
Little research had been carried out on the specimen since its arrival at the museum in 1919, Hunterian paleontology curator Neil Clark said.
"It is comforting to know that new species can still be found in museums as new research is carried out on old collections," he said. "It is not just the new species that are important, but an increase in our understanding of how life evolved and the variety of life forms that existed 163 million years ago in the warm Jurassic seas around what is now Britain."