Anura, comprised of frogs or toads, is the most diverse of the three existing amphibian orders. There is no formal distinction between frogs and toads, just that toads are typically a more warty frog species. Frogs live in every biome except in extremely dry deserts and polar regions, however, their species diversity is most abundant in the tropics. Frogs are typically carnivores though some eat fruit, and all adult frogs, except one species, do not have tails—thus where the the name Anura, meaning “without tail,” came from. There are about 4,000 different species of frogs with the earliest known fossils dating back to the Jurassic period.