Bulgaria is a country in southeastern Europe situated entirely in the Balkan peninsula. Bulgaria is inhabited by 22 amphibian species, which makes the amphibians the least diverse class of vertebrates in the country. They include nine species of newts and salamanders from a single family, Salamandridae, as well as 13 frog and toad species from five families—Bombinatoridae, Bufonidae, Hylidae, Pelobatidae and Ranidae. The most recently classified species are the northern crested newt, identified in 2005, and the Macedonian crested newt, identified in 2007. In 2017 genetic studies suggested that the smooth newt was a species complex and was split in six species, of which three are fount in Bulgaria—the smooth newt "sensu lato", the Greek smooth newt and the Schmidtler's smooth newt. Some of the most common species include the European green toad, yellow-bellied toad, and marsh frog.