A cloven hoof is a hoof split into two toes. This is found on members of the mammalian order Artiodactyla. Examples of mammals that possess this type of hoof are deer and sheep. In folklore and popular culture, a cloven hoof has long been associated with the Devil.
The two digits of cloven hoofed animals are homologous to the third and fourth fingers of the hand. They are called claws and are named for their relative location on the foot: the outer, or lateral, claw and the inner, or medial claw. The space between the two claws is called the interdigital cleft; the area of skin is called the interdigital skin. The hard outer covering of the hoof is called the hoof wall, or horn. It is a hard surface, similar to the human fingernail.
The almost finger-like dexterity available to cloven hoofed mammals like the Mountain Goat and Mountain Sheep combined with a hard outer shell and soft and flexible inner pads provide excellent traction in their precarious habitats.
It is speculated that during the Eocene period, hoofed marsh dwellers carried their body weight mainly on two of the middle toes, which grew to equal size, becoming the Artiodactyla or even-toed hoofed animals. Prior to the close of the Eocene period the side toes of some had dwindled and practically disappeared while the basal pieces or metapodium of the pair of supporting toes became fused together, thus producing the appearance of a cloven hoof.
The mammal with a cloven hoof is an even-toed ungulate of order Artiodactyla as opposed to the odd-toed ungulates of Perissidactyla, like the horse, which have one toe, or the rhinoceros, which has three toes. The five-toed ancestors of the earliest Eocene had already developed feet that suggest odd-toed and even-toed descendants to the modern viewer. Even Phenacodus, the most generalized of the early mammals, has a foot in which the central toe is somewhat larger than the others and could be placed in the division of odd toed ungulates, Perissidactyla. 
Cloven hooves in culture 
Unclean animals in religion 
The distinction between cloven and uncloven hooves is highly relevant for dietary laws of Judaism (Kashrut), as set forth in the Torah and the Talmud. Animals that both chew their cud (ruminate) and have cloven hooves are allowed (kosher), whereas those that have only one of these two characteristics are considered unclean animals and Jews are forbidden to eat them. This rule excludes from the diet the camel because it ruminates but has no cloven hooves, and the pig because it has cloven hooves but does not ruminate.
The Devil 
The cloven hoof is also traditionally associated with the Devil. In works from Shakespeare and Sir Thomas Browne the association is very close and the devil takes pains to hide or disguise the hoof. In other works the Devil and the cloven hoof can be separated, some believe the cloven hoof more mischievous than the devil. But not every cloven hoof is the devil's minion.  In Teutonic Mythology the devil has a non-cloven hoof that is solid like that of a horse, from which he can not be separated.
According to a folk legend, in 1165, the Devil rode like a great black horse before a storm in Yorkshire. The marks of his feet were visible in several places, particularly on the cliff at Scarborough, where he sprang into the sea. In the late 1800s, marks were discovered in various parts the South of England that could not be identified as any known beast or bird. People did not like to say it was the Devil, but no other explanation was offered. Perhaps this extraordinary presence may have been nothing more than cloven hoofs, which in the deep snows of winter are said to haunt the Dewerstone a rocky elevation on the borders of Dartmoor—but this latter phenomenon is reported to be accompanied by a naked human foot. A case occurred in Devonshire and are many cases are collected in "Lancashire Folk Lore" 1867. 
- American Museum of Natural History (1892). Visitors' Guide to the Geological and Palaeontological Collections. Original from the University of Michigan. p. 59.
- "Hoof Anatomy, Care and Management in Livestock" (PDF). Purdue University. October 2004. Retrieved 2007-12-02.
- Jackson, Brenda (1998). North American Wildlife (Revised and Updated). Readers Digest. p. 68. ISBN 0-7621-0020-6.
- Streubel, Donald (2000). "Oreamnos americanus (Mountain Goat)" (Web). Idaho Museum of Natural History. Retrieved 2007-12-02.
- Plekon, Hannah J. (April 2007). "Oreamnos americanus; General description" (Web). Davidson College. Retrieved 2007-12-03.
- British Museum (Natural History) (1906). British Museum Guides: Vertrbrates. Original from the University of Michigan. p. 28.
- Cleland, Herdman Fitzgerald (1916). Geology, Physical and Historical. Original from the University of Michigan: American book company. p. 599.
- Leviticus 11:3-8
- Shulchan Aruch, Yoreh De'ah 79
- Slifkin, Nosson (March 1, 2004). 6 (PDF). "Shafan– The Hyrax". The camel, the hare & the hyrax: a study of the laws of animals with one kosher sign in light of modern zoology. Southfield, MI; Nanuet, NY: Zoo Torah in association with Targum/Feldheim Distributed by Feldheim. pp. 99–135. ISBN 1-56871-312-6. Retrieved April 25, 2012. ISBN 978-1-56871-312-0.
- Glover, Alfred Kingsley (1900). Jewish Laws and Customs: Some of the Laws and Usages of the Children of the Ghetto. Original from Harvard University: W.A. Hammond. p. 157.
- Eisenberg, Ronald L. (2005). The 613 Mitzvot: A Contemporary Guide to the Commandments of Judaism. Schreiber Publishing, Incorporated. p. 251. ISBN 0-88400-303-5.
- Massey, Gerald (1866). Shakespeare's Sonnets Never Before Interpreted: His Private Friends Identified. Original from the University of California: Longmans, Green, and co. p. 518.
- Sir Thomas Browne (1878). The Works of Sir Thomas Browne. Original from Oxford University. p. 79.
- Jefferies, John Richard (1874). The scarlet shawl. Original from Oxford University. p. 176.
- Defoe, Daniel (1871). The Novels and Miscellaneous Works of Daniel Defoe. Original from Oxford University: Bell & Daldy. p. 515.
- Edited by SYLVANUS URBAN (1896). The Gentleman's Magazine: Diabolical Folk Lore in Divers Places. p. 482.
- Grimm, Jacob; Translated by James Steven Stallybrass (1882). Teutonic mythology. Original from Oxford University: G. Bell. p. 281.
- Brand, John (1905). Brand's Popular Antiquities of Great Britain: Faiths and Folklore; a Dictionary. Reeves and Turner. p. 176.