 The rails are a bird family comprising nearly 150 species . Although the origins of the group are lost in antiquity , the largest number of species and the most primitive forms are found in the Old World , suggesting that this family originated there . However , the genus Rallus , the group of long @-@ billed reed bed specialists to which the water rail belongs , arose in the New World . Its Old World members , the Water , African and Madagascan rails , form a superspecies , and are thought to have evolved from a single invasion from across the Atlantic . Genetic evidence suggests that the water rail is the most closely related of its genus to the Pacific Gallirallus rails , and is basal to that group . The water rail was first described by Linnaeus in his Systema Naturae in 1758 under its current scientific name , Rallus aquaticus . The binomial name is the Latin equivalent of the English " water rail " . 
