Like the 18th-century German naturalist August Johann Rösel von Rosenhof, whose beautifully illustrated Historia naturalis ranarum nostratium (Natural history of the native frogs) he describes in an essay in Natural Histories, Curator Darrel R. Frost has created a comprehensive reference about amphibians. He manages Amphibian Species of the World, an online database and classification system for about 7,000 amphibian species, of which about 6,200 are frogs.