In biology

Biology

Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, dactyly is the arrangement of digits (finger

Finger

A finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates....

s and toe

Toe

Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, and other animals that walk on the soles of their feet, are described as being plantigrade; unguligrade animals are those that walk on hooves at the tips of...

s) on the hand

Hand

A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...

s, feet, or sometimes wing

Wing

A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...

s of a tetrapod

Tetrapod

Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...

 animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

. It comes from the Greek word δακτυλος = "finger".

Sometimes the ending "-dactylia" is used. The derived adjectives end with "-dactyl" or "-dactylous".

Tetradactyly

Tetradactyly (from Greek tetra-="four" plus δακτυλος = "finger") is the condition of having four digits on a limb, as in many amphibian

Amphibian

Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

s, bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s, and theropod dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

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

Rhinoceros

Rhinoceros , also known as rhino, is a group of five extant species of odd-toed ungulates in the family Rhinocerotidae. Two of these species are native to Africa and three to southern Asia....

 and ancestors of the horse such as Protohippus

Protohippus

Protohippus is an extinct genus of horse....

and Hipparion

Hipparion

Hipparion is an extinct genus of horse living in North America, Asia, Europe, and Africa during the Miocene through Pleistocene ~23 Mya—781,000 years ago, existing for...

. These all belong to the Perissodactyla. Some birds also have three toes, including emus, bustards, and quail

Quail

Quail is a collective name for several genera of mid-sized birds generally considered in the order Galliformes. Old World quail are found in the family Phasianidae, while New World quail are found in the family Odontophoridae...

.

Didactyly

Didactyly (from Greek di-="two" plus δακτυλος = "finger") or bidactyly is the condition of having two digits on each limb, as in the Hypertragulidae

Hypertragulidae

Hypertragulidae is an extinct family of even-toed ungulates , endemic to North America, Europe, and Asia during the Eocene through Miocene, living 46.2—13.6 Ma, existing for approximately ....

 and Two-toed Sloth

Two-toed sloth

Choloepus is a genus of mammals of Central and South America, within the family Megalonychidae consisting of two-toed sloths. There are only two species of Choloepus : Linnaeus's Two-toed Sloth and Hoffmann's 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

Horse

The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...

s. These belong to the Perissodactyla.

Syndactyly

Syndactyly

Syndactyly

Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and kangaroo, but is an unusual condition in humans.-Classification:...

 (from Greek συν- = "together" plus δακτυλος = "finger") is a condition where two or more digits are fused together. It occurs normally in some mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s, such as the siamang

Siamang

The siamang is a tailless, arboreal, black-furred gibbon native to the forests of Malaysia, Thailand, and Sumatra. The largest of the lesser apes, the siamang can be twice the size of other gibbons, reaching 1 m in height, and weighing up to 14 kg...

 and most diprotodontid marsupial

Marsupial

Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...

s such as kangaroos

KangaROOS

KangaROOS are an American brand of sneaker originally produced from 1979 through the 1980s, with a later revival that continues in present. They were notable for having a small zippered pocket on the side of the shoe, large enough for a small amount of loose change, keys, or more recently,...

. It occurs as an unusual condition in humans.

Polydactyly

Polydactyly

Polydactyly

Polydactyly or polydactylism , also known as hyperdactyly, is a congenital physical anomaly in humans, dogs, and cats having supernumerary fingers or toes....

 (from Greek πολυ- = "many" plus δακτυλος = "finger") is when a limb has more than the usual number of 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
  Polydactyly
  Polydactyly or polydactylism , also known as hyperdactyly, is a congenital physical anomaly in humans, dogs, and cats having supernumerary fingers or toes....
  
  .
• Polydactyly in early tetrapod aquatic animal
  Aquatic animal
  An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
  
  s, 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. The use of a term normally reserved for congenital defects reflects that it was regarded as an anomaly at the time, as it was believed that all modern tetrapods have either five digits or ancestors that did.

Oligodactyly

Oligodactyly (from Greek ὀλιγο- = "few" plus δακτυλος = "finger") is having too few digits when not caused by an amputation

Amputation

Amputation is the removal of a body extremity by trauma, prolonged constriction, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on individuals as a preventative surgery for...

. It is sometimes incorrectly called hypodactyly or confused with aphalangia, the absence of the phalanx bone on one or (commonly) more digits. When all the digits on a hand or foot are absent, it is referred to as adactyly.

Ectrodactyly

Ectrodactyly

Ectrodactyly

Ectrodactyly, sometimes referred to as the “Lobster-Claw Syndrome” involves the deficiency or absence of one or more central digits of the hand or foot and is also known as split hand/split foot malformation...

, also known as split-hand malformation, is the congenital absence of one or more central digits of the hands and feet. Consequently, it is a form of oligodactyly. News anchor Bree Walker

Bree Walker

Bree Walker is a radio talk show host, actress, and disability-rights activist, who gained fame as the first on-air American television network news anchor with ectrodactyly. Walker worked as a news anchor and/or reporter in San Diego, New York City, and Los Angeles.Walker was born in Oakland,...

 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

Vadoma

The Doma, also Vadoma or Wadoma , are a tribe living in the west of Zimbabwe, especially in the Urungwe and Sipolilo districts on the Zambezi river valley...

 in Zimbabwe

Zimbabwe

Zimbabwe is a landlocked country located in the southern part of the African continent, between the Zambezi and Limpopo rivers. It is bordered by South Africa to the south, Botswana to the southwest, Zambia and a tip of Namibia to the northwest and Mozambique to the east. Zimbabwe has three...

.

Anisodactyly

Anisodactyly is the most common arrangement of digits in birds, with three toes forward and one back. This is common in songbird

Songbird

A songbird is a bird belonging to the suborder Passeri of the perching birds . Another name that is sometimes seen as scientific or vernacular name is Oscines, from Latin oscen, "a songbird"...

s and other perching birds, as well as hunting birds like eagle

Eagle

Eagles are members of the bird family Accipitridae, and belong to several genera which are not necessarily closely related to each other. Most of the more than 60 species occur in Eurasia and Africa. Outside this area, just two species can be found in the United States and Canada, nine more in...

s, hawk

Hawk

The term hawk can be used in several ways:* In strict usage in Australia and Africa, to mean any of the species in the subfamily Accipitrinae, which comprises the genera Accipiter, Micronisus, Melierax, Urotriorchis and Megatriorchis. The large and widespread Accipiter genus includes goshawks,...

s, and falcon

Falcon

A falcon is any species of raptor in the genus Falco. The genus contains 37 species, widely distributed throughout Europe, Asia, and North America....

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

Belted Kingfisher

The Belted Kingfisher is a large, conspicuous water kingfisher, the only member of that group commonly found in the northern United States and Canada. It is depicted on the 1986 series Canadian $5 note. All kingfishers were formerly placed in one family, Alcedinidae, but recent research suggests...

 Ceryle alcyon. This is characteristic of Coraciiformes

Coraciiformes

The Coraciiformes are a group of usually colorful near passerine birds including the kingfishers, the Hoopoe, the bee-eaters, the rollers, and the hornbills...

 (Kingfisher

Kingfisher

Kingfishers are a group of small to medium sized brightly coloured birds in the order Coraciiformes. They have a cosmopolitan distribution, with most species being found in the Old World and Australia...

s, Bee-eater

Bee-eater

The bee-eaters are a group of near-passerine birds in the family Meropidae. Most species are found in Africa and Asia but others occur in southern Europe, Australia, and New Guinea. They are characterised by richly coloured plumage, slender bodies, and usually elongated central tail feathers...

s, Roller

Roller

The rollers are an Old World family, Coraciidae, of near passerine birds. The group gets its name from the aerial acrobatics some of these birds perform during courtship or territorial flights. Rollers resemble crows in size and build, and share the colourful appearance of kingfishers and...

s, and relatives).

Zygodactyly

Zygodactyly (from Greek ζυγον, a yoke

Yoke

A yoke is a wooden beam, normally used between a pair of oxen or other animals to enable them to pull together on a load when working in pairs, as oxen usually do; some yokes are fitted to individual animals. There are several types of yoke, used in different cultures, and for different types of oxen...

) 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

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

 trunks or clamber through foliage. Zygodactyly occurs in the parrot

Parrot

Parrots, also known as psittacines , are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes, found in most tropical and subtropical regions. The order is subdivided into three families: the Psittacidae , the Cacatuidae and the Strigopidae...

s, woodpecker

Woodpecker

Woodpeckers are near passerine birds of the order Piciformes. They are one subfamily in the family Picidae, which also includes the piculets and wrynecks. They are found worldwide and include about 180 species....

s (including flickers), cuckoo

Cuckoo

The cuckoos are a family, Cuculidae, of near passerine birds. The order Cuculiformes, in addition to the cuckoos, also includes the turacos . Some zoologists and taxonomists have also included the unique Hoatzin in the Cuculiformes, but its taxonomy remains in dispute...

s (including roadrunners

Geococcyx

The roadrunners are two species of bird in the genus Geococcyx of the cuckoo family, Cuculidae, native to North and Central America...

), and some owls

OWLS

OWLS is a mnemonic used by general aviation airplane pilots to assess an unprepared surface for a precautionary landing.Like all mnemonics this check has become part of aviation culture and folklore.OWLS:* Obstacles* Wind direction...

. Zygodactyl tracks have been found dating to 120-110 Ma (early Cretaceous

Cretaceous

The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

), 50 million years before the first identified zygodactyl fossils.

Heterodactyly

Heterodactyly is like zygodactyly, except that digits 3 and 4 point forward and digits 1 and 2 point back. This is found only in trogon

Trogon

The trogons and quetzals are birds in the order Trogoniformes which contains only one family, the Trogonidae. The family contains 39 species in eight genera. The fossil record of the trogons dates back 49 million years to the mid-Eocene. They might constitute a member of the basal radiation of...

s.

Pamprodactyl

Pamprodactyl is an arrangement in which all four toes point forward. It is a characteristic of swift

Swift

The swifts are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows, but are actually not closely related to passerine species at all; swifts are in the separate order Apodiformes, which they share with hummingbirds...

s (Apodidae).

Chameleons

The feet of chameleons are fused into a group of two and a group of three toes which oppose one another to grasp branches in a pincer-like arrangement. This has been called zygodactyly or didactyly, though the details of the arrangements differ.

Schizodactyly

Schizodactyly is a primate

Primate

A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...

term for grasping and clinging with the second and third digit, instead of the thumb and second digit.