Dactyly
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2008-07-01T10:56:10Z
Secret Squïrrel
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Theropods have four toes - moved to correct section, other minor fixes
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In [[biology]], '''dactyly''' is the arrangement of [[wikt:digit|digits]] ([[finger]]s and [[toe]]s) on the [[hand]]s, [[Foot|feet]], or sometimes [[wing]]s of a [[tetrapod]] [[animal]]. It comes from the [[Greek (language)|Greek]] word δακτυλος = "finger".
Sometimes the ending "-dactylia" is used. The derived adjectives end with "-dactyl" or "-dactylous".
==Pentadactyly==
Pentadactyly (from [[Greek language|Greek]] pente-="five" plus δακτυλος = "finger") is the condition of having five digits on each limb. It is believed that all living tetrapods are descended from an ancestor with a pentadactyl limb, although many species have now lost or transformed some or all of their digits by the process of [[evolution]]. Despite the individual variations listed below, the relationship is to the original five-digit 'model'.
==Tetradactyly==
Tetradactyly (from Greek tetra-="four" plus δακτυλος = "finger") is the condition of having four digits on a limb, as in many [[amphibian]]s, [[bird]]s, and [[theropod]] [[dinosaur]]s. Some mammals also exhibit tetradactyly (for example pigs and the hind limbs of dogs and cats). Cartoon characters are commonly drawn with four digits on each hand/foot as it's clearer to see than five.
==Tridactyly==
Tridactyly (from Greek tri- = "three" plus δακτυλος = "finger") is the condition of having three digits on a limb, as in the [[Rhinoceros]] and ancestors of the horse such as ''[[Protohippus]]'' and ''[[Hipparion]]''. These all belong to the [[Perissodactyla]]. Some birds also have three toes, including [[emus]], [[bustards]], and [[quail]].
==Didactyly==
Didactyly (from Greek di-="two" plus δακτυλος = "finger") or bidactyly is the condition of having two digits on each limb, as in the [[Two-toed Sloth]], ''Choloepus didactylus''. In humans this name is used for an abnormality in which the middle digits are missing, leaving only the thumb and fifth finger, or big and little toes. Cloven-hoofed mammals (such as deer, sheep and cattle - '[[Artiodactyla]]') have only two digits, as do [[ostriches]].
==Monodactyly==
Monodactyly (from Greek monos- = "one" plus δακτυλος = "finger") is the condition of having a single digit on a limb, as in modern [[horse]]s. These belong to the [[Perissodactyla]].
==Syndactyly==
[[Image:Celldeath.jpg|thumb|Human foot with partial simple syndactyly.]]
[[Syndactyly]] (from Greek συν- = "together" plus δακτυλος = "finger") is a condition where two or more digits are fused together. It occurs normally in some [[mammal]]s, such as the [[siamang]] and most [[diprotodont]]id [[marsupial]]s such as [[kangaroos]]. It occurs as an unusual condition in humans.
==Polydactyly==
[[Polydactyly]] (from Greek πολυ- = "many" plus δακτυλος = "finger") (or '''hyperdactyly''', from Greek hyper- = "too many" plus δακτυλος = "finger") is when a limb has more than five digits. This can be:-
*As a result of congenital abnormality in a normally pentadactyl animal. Polydactyly is very common among domestic cats. For more information, see [[polydactyly]].
*Normality in some early [[tetrapod]] aquatic animals, such as ''[[Acanthostega gunnari]]'' (Jarvik 1952), which is one of an increasing number of genera of stem-tetrapods known from the Upper [[Devonian]], which are providing insights into the appearance of tetrapods and the origin of limbs with digits. It also occurs secondarily in some later tetrapods, such as [[ichthyosaurs]].
==Hypodactyly==
Hypodactyly (from Greek hypo- = "too few" plus δακτυλος = "finger") is having too few digits when not caused by an [[amputation]].
==Ectrodactyly==
[[Ectrodactyly]] is the congenital absence of all or part of one or more fingers or toes. This term is used for a range of conditions from '''aphalangia''' (in which some of the [[phalanges]] or finger bones are missing), to '''adactyly''' (the absence of a digit).
A fusing of almost all digits on all of the hands and feet is '''ectrodactyly'''. News anchor [[Bree Walker]] is probably the best-known person with this condition, which affects about one in 91,000 people. It is conspicuously more common in the [[Vadoma]] in [[Zimbabwe]].
==Schizodactyly==
'''Schizodactyly''' is a [[primate]] term for grasping and clinging with the second and third digit, instead of the thumb and second digit.
==In birds==<!-- This section is linked from [[Parrot]] -->
[[Image:Bird-feets.png|thumb|types of bird feet]]
===Anisodactyly===
Anisodactyly is the most common arrangement of digits in birds, with three toes forward and one back. This is common in [[songbird]]s and other [[perching bird]]s, as well as hunting birds like [[eagle]]s, [[hawk]]s, and [[falcon]]s.
===Syndactyly===
Syndactyly, as it occurs in birds, is like anisodactyly, except that the third and fourth toes (the outer and middle forward-pointing toes), or three toes, are fused together, as in the [[Belted Kingfisher]] ''Ceryle alcyon''. This is characteristic of [[Coraciiformes]] ([[Kingfisher]]s, [[Bee-eater]]s, [[Roller]]s, and relatives).
===Zygodactyly===
Zygodactyly (from Greek ζυγον, a [[yoke]]) is an arrangement of digits in birds, with two toes facing forward (digits 2 and 3) and two back (digits 1 and 4). This arrangement is most common in [[arboreal]] species, particularly those that climb [[tree]] trunks or clamber through foliage. Zygodactyly occurs in the [[woodpecker]]s (including [[flicker (bird)|flicker]]s), in some [[owls]], in [[cuckoo]]s, and in [[parrot]]s.
===Heterodactyly===
Heterodactyly is like zygodactyly, except that digits 3 and 4 point forward and digits 1 and 2 point back. This is only found in [[trogon]]s.
===Pamprodactyly===
Pamprodactyly is an arrangement in which all four toes point forward. It is a characteristic of [[swift]]s ([[Apodidae]]).
{{Congenital malformations and deformations of musculoskeletal system}}
[[Category:Zoology]]
[[Category:Anatomy]]
[[Category:Comparative anatomy]]
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