Sloths from Frederic Cuvier's 'Dictionary of Natural Science: Mammals,' Paris, 1816

Maned three-toed sloth, Bradypus torquatus (vulnerable), and Linnaeus's two-toed sloth, Choloepus didactylus. Handcoloured copperplate stipple engraving from Frederic Cuvier's 'Dictionary of Natural Science: Mammals,' Paris, France, 1816. Illustration by J. G. Pretre, engraved by Massard, directed by Pierre Jean-Francois Turpin, and published by F.G. Levrault. Jean Gabriel Pretre (1780-1845) was painter of natural history at Empress Josephine's zoo and later became artist to the Museum of Natural History. Turpin (1775-1840) is considered one of the greatest French botanical illustrators of the 19th century. . (Photo by: Florilegius/Universal Images Group via Getty Images)