A species is a group of living things reproductively isolated from other groups. The plural of species is species. Specie means money, specifically, coined money.
Other false singulars: Phenomena is plural; its singular is phenomenon. Series is both singular and plural; the singular is not serie. Bacterium is the singular; bacteria is the plural. Criterion: singular; criteria: plural. Biceps is the singular. Bicepses is the plural, though you can use biceps if you insist. There is no such thing as a bicep. Or a tricep. Or a quadricep.
The human species is Homo sapiens. An individual human is still Homo sapiens, not Homo sapien.