In 1758, in his seminal work "Systema Naturae", Linnaeus (1707–1778) classified horses ("Equus") together with hippos ("Hippopotamus"). At that time, this category also included the tapirs ("Tapirus"), more precisely the lowland or South American tapir ("Tapirus terrestus"), the only tapir then known in Europe. Linnaeus classified this tapir as "Hippopotamus terrestris" and put both genera in the group of the "Belluae" ("beasts"). He combined the rhinos with the Glires, a group now consisting of the lagomorphs and rodents. Mathurin Jacques Brisson (1723–1806) first separated the tapirs and hippos in 1762 with the introduction of the concept "le tapir". He also separated the rhinos from the rodents, but did not combine the three families now known as the odd-toed ungulates. In the transition to the 19th century, the individual perissodactyl genera were associated with various other groups, such as the proboscidean and even-toed ungulates. In 1795, Étienne Geoffroy Saint-Hilaire (1772–1844) and Georges Cuvier (1769–1832) introduced the term "pachyderm" (Pachydermata), including in it not only the rhinos and elephants, but also the hippos, pigs, peccaries, tapirs and hyrax . The horses were still generally regarded as a group separate from other mammals and were often classified under the name "Solidungula" or "Solipèdes", meaning "one-hoof animal".