The dromedary shares the genus "Camelus" with the Bactrian camel ("C. bactrianus") and the wild Bactrian camel ("C. ferus"). The dromedary belongs to the family Camelidae. The ancient Greek philosopher Aristotle (4th century BC) was the first to describe the species of "Camelus". He named two species in his "History of Animals"; the one-humped Arabian camel and the two-humped Bactrian camel. The dromedary was given its current binomial name "Camelus dromedarius" by Swedish zoologist Carl Linnaeus in his 1758 publication "Systema Naturae". In 1927, British veterinarian Arnold Leese classified dromedaries by their basic habitats; the hill camels are small, muscular animals and efficient beasts of burden; the larger plains camels could be further divided into the desert type that can bear light burdens and are apt for riding, and the riverine type – slow animals that can bear heavy burdens; and those intermediate between these two types.