The BBC reports that student Roy Smith discovered the fossils of the mysterious storehouse after searching collections at the Setwick Museum in Cambridge and the Booth Museum in Brighton.
The collection of fossils he examined was collected in southern England between 1851 and 1900.
Mr Smith, who is studying at the University of Portsmouth, said previous researchers had not noticed the key details.
“One such feature is the tiny little holes where the veins come to the surface and are used for sensitive food,” Mr Smith said.
“Shark paddle vertebrates do not have these, but early archaeologists missed these features.
“The two specimens found can be identified as a steroid called ornithostoma, but one additional specimen is clearly different and refers to a new species – which is an ancient mystery.”
Mr. Smith, the new species cannot be named because the model is so fragmented.
He said more fossils are unlikely to be found as the rock is no longer exposed.
But Mr Smith said he would continue to search for reptile remains in other museum collections when the UK lifts epidemic controls.