How many mammal species are there?

355.

As presented in the Living Planet Report 2008, issued by WWF International, there are 355 mammal species on earth. Among them, 292 belong to the terrestrial system, 49 to the marine system and 14 to the freshwater system. From 1970 to 2005, the number of mammal species decreased 19%. Mammals represent 21% of all vertebrates in the world.