A researcher at Coventry University is championing the British ancestry of an extinct frog.
Chris Gleed-Owen's research will determine whether the pool frog was officially Britain's seventh species of amphibian or an illegal immigrant. The pool frog's case will be presented to English Nature to make a decision about the species' future.
Lucky, the last of the pool frogs, died of old age last month, aged 11.
Pool frogs started declining when their fenland habitat was drained in the 1600s. Records of the species date back to the early 1800s, but it was often confused with the Edible Frog, introduced by naturalists about the same time.
English Nature will reintroduce the pool frog only if it can be proven that it is a native species. Dr Gleed-Owen has looked for archaeological remains from almost 40 sites. One pool frog bone comes from Gosberton, Lincolnshire, and dates back to AD600-900.
Lucky had been bred with other European pool frogs, so offspring with British genes exist and could be brought back.
Tony Gent of English Nature said: "By April 2000 we will know for sure and can decide whether we should begin reintroducing the pool frog to East Anglia."