During the early Devonian period, approximately 400 million years ago, Lungfish appeared in the fossil record. They are an ancient group of fish and, along with two extant species of coelacanth, are the only surviving lobe-finned fishes. Lungfish are among the most closely related species to terrestrial vertebrates. Six species of extant lungfish from three families, Ceratodontidae, Lepidosirenidae, and Protopteridae, are currently known. Neoceratodus forsteri is the only species in the family Ceratodontidae and is found in Australia. Lepidosiren paradoxa is the sole representative of the family Lepidosirenidae and is found in South America. The family Protopteridae comprises four species, namely Protopterus amphibius, P. aethiopicus, P. annectens, and P. dolloi, which are all restricted to Africa.