The Chadwick Beach cotton mouse (Peromyscus gossypinus restrictus) was a rare subspecies of the cotton mouse (Peromyscus gossypinus) that was known only on a small area of Manasota Key.
Fifteen specimens of the Chadwick Beach cotton mouse were captured by a researcher in 1938, and in so doing, he may have contributed to wiping out the very tiny species. They soon vanished, though deforestation and predation by cats have been alternately blamed. The mouse is now presumed extinct after extensive surveys in the 1980s failed to find a single example of it.
It was smaller and paler than the common cotton mouse - so named because it likes to build nests from wild cotton - and had a white/pink belly. It also differed from common cotton mice with its smaller dorsal stripe.
As Florida becomes more and more populated, there's no telling how many more species not even discovered have come and gone, with mankind oblivious and unaware.