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http://animaldiversity.ummz.umich.edu/chordata/mammalia/



Order Perissodactyla

The name Perissodactyla means "odd-toed." This group of ungulates includes horses, tapirs, and rhinos. The name of their order derives from the fact that their middle toe is larger than the others, and the plane of symmetry of the foot passes through it, a condition called mesaxonic. Most species have three digits on the hindfoot and three or four on the forefoot, but in some only a single digit, the third, remains. Some species have horns, but these are dermal structures without bony cores, and they are located on the nasals or frontals in the midline of the skull. This contrasts with the horns of artiodactyls, which have bone cores, are paired, and are located on the frontals. The anterior part of the skull of perissodactyls is elongated and accomodates a full series of large cheek teeth (most have a total of 44 teeth). Molars and premolars are hypsodont in grazing forms such as horses, and brachydont in browsers such as tapirs. Modern species are lophodont (complexly so in equids), in contrast to artiodactyls, which tend to be selenodont or bunodont. Perissodactyls have a simple stomach, in contrast to the chambered structure of most artiodactyls. Their cecum is enlarged and sacculate, and in it some bacterial digestion of cellulose takes place.

Early in the Tertiary, this was a dominant group that included 14 families and many species. One extinct species of rhinoceros, Indricotherium ( = Baluchitherium), was the largest land mammal that ever lived, standing approximately 5.4 m tall at the shoulder and weighing around 30,000 kg (5 times the weight of modern elephants!). Now, all that remain are 3 living families, with 18 species in all. Their decline accelerated during the Oligocene and coincided with the rise of another group of large herbivorous and cursorial mammals, the artiodactyls. 

Modern perissodactyls are native to Africa, south and central Asia, southern North America, and northern South America. Most species are herbivorous.

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Literature and references cited

Carter, D. C.. 1984. Perissodactyls. Pp. 549-562 in Anderson, S. and J. K. Jones, Jr. (eds). Orders and Families of Recent Mammals of the World. John Wiley and Sons, N.Y. xii+686 pp.

Savage, R. J. G. and M. R. Long. 1986. Mammal Evolution, an Illustrated Guide. Facts of File Publications, New York. 259 pp.

Vaughan, T. A. 1986. Mammalogy. Third Edition. Saunders College Publishing, Fort Worth. vii+576 pp.

 

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Click on a name below to find out more about that Family:



Family Equidae
Family Tapiridae
Family Rhinocerotidae


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Equidae

(horses)

This family, made up of the horses, asses and zebras, contains one genus with nine species. Domestic equids range worldwide; in the wild equids occur mainly in East Africa and the Near East to Mongolia. They inhabit a variety of habitats from lush grasslands and savanna to sandy and stony deserts.

Equids are generally thick-skulled animals with stocky bodies. They are heavily haired, but the length of hair is variable. Most species have a mane on the neck and a lock of hair on the forepart of the head known as a forelock. Some are swift runners: these have long thin limbs with only one functional digit (mesaxonic). Equids walk on the tips of their toes (unguligrade). In the equid foreleg, radius and ulna are united, and the ulna is greatly reduced so that all weight is born on the radius. In the hind leg, the enlarged tibia supports the weight and the fibula is reduced and fused to the tibia. Wild equids are large animals, ranging in body size from around 200 to 500 kg. Their domestic descendants are more variable, varying from less than 140 kg to over 1000 kg.

Equids have 40-42 teeth with a dental formula 3/3, 1/1, 3-4/3, 3/3. The canines are vestigial or absent in females. Their cheek teeth have a complex structure; they are hypsodont with four main columns and various infoldings with much cement. Age of an equid is often estimated by the degree to which surface pattern of cheek teeth is worn, but the abrasive character of food plays too large a role in tooth wear to make this entirely accurate.

Equid skulls are long with the nasal bones long, narrow and freely projecting anteriorly to points. The orbit is far back in the skull, behind the teeth, and the postorbital processes are broad. Tympanic bullae are small.

Females come into heat several times a year or until they become pregnant. Most species give birth every 2 years to a single offspring after a gestation period of 11-13 months. Weaning occurs after about 6-8 months and offspring become sexually mature at about 2 years. Potential lifespan is 25-35 years.

All equids are relatively swift, alert runners and generally flee from danger rather than fight. However, among their own kind or in attempting defense, they kick with the hind feet, strike with the forefeet and sometimes bite. Equids are active both day and night but are mainly crepuscular. They are entirely herbivorous, feeding largely on grass and some browse. Most drink water daily, although they can go without water for long periods of time.

Equids are polygynous herd animals that generally live in extended family groups occupying large territories in open country (grasslands, semi-arid areas, deserts, and mountains). Communication of moods and other information takes place with changes in ear, mouth, and tail positions. Also, some vocal communication through nickering takes place in horses and zebras.

The fossil record of horses is especially rich. It has provided classic examples that supposedly document gradual change in teeth and limbs. The first horse, Hyracotherium (=Eohippus), is known from the early Eocene and appears to have been derived from a condylarth. It was a small animal with relatively simple quadrate teeth, a modestly enlarged third metacarpal, and digitigrade stance. Through the Oligocene, Miocene, and Pliocene horses increased in size, their lateral digits shrank and lost contact with the ground, their brains enlarged, and their molariform teeth became much more complex. The first true grazer, Merychippus, lived in Miocene times. Its cheek teeth were hypsodont and had strongly developed lophs on their occlusal surfaces. Three of its toes contacted the ground. The first one-toed horse, Pliohippus, lived in the late Miocene. The genus Equus first appeared during the Pliocene. Horses were once widespread, inhabiting temporal grasslands, savannahs, and steppe habitats through North America, Asia, Africa, and Europe. North America has been the center of equid evolution. Equids disappeared completely from that continent around 8000 years ago, not to return until Europeans brought them in their ships a few hundred years ago.

Technical characters

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Species included in the Animal Diversity Web:


  Equus asinus (Ass) -pt- 
  Equus burchellii (Burchell's or Plains Zebra) -pt- 
  Equus caballus (Domestic Horse) -ta- 
  Equus caballus przewalskii (Przewalski's Wild Horse, Mongolian Wild Horse) -t- 
  Equus grevyi (Grevy's Zebra) -pt- 
  Equus hemionus (Asian Wild Ass) -t- 
  Equus kiang (Wild Ass) -t- 
  Equus quagga (Quagga) -t- 
  Equus zebra (Mountain Zebra) -t- 


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Tapiridae

(tapirs)

The family Tapiridae contains tapirs. They are placed in one genus, Tapirus, with four species. Three of these species live in South America, ranging from southern Mexico through central America to Venezuela, and south to Paraguay and Brazil. The fourth species, the Malayan tapir, inhabits Burma and Thailand south to Malaya and Sumatra. Tapirs are shy, reclusive rainforest animals that live in nearly any wooded or grassy habitat with a permanent supply of water. They have also been found in dry deciduous forests and mountain forests.

Species included in the Animal Diversity Web:
  Tapirus bairdii (Baird's Tapir) -t- 
  Tapirus indicus (Malayan Tapir) -pta- 
  Tapirus pinchaque (Mountain Tapir) -t- 
  Tapirus terrestris (Brazilian Tapir) -ta- 

Accounts marked with a p contain pictures, t contain narrative text (student authored), a contain anatomical still/QTVR images, and s contain digitized sound clips. 

Tapirs are about the size of a donkey. Their body is rounded in back and tapering in front-- well suited for rapid movement through thick underbrush. They also have a very short tail. Tapirs have bristly hairs scattered all over the body, and an inconspicuous mane is present on two of the South American species. All the South American tapirs are uniform dark brown or gray in color, whereas the Malayan tapir is black on its hind legs and the entire front of its body, and creamy white through its midsection. All tapirs have a short, fleshy proboscis formed by the snout and upper lips. This proboscis is more elongated in the South American species. Tapir eyes are small and flush with the side of the head; their ears are oval, erect, and not very mobile.

Skeletal features include short, slender legs with radius and ulna separate and equally developed. The fibula is also complete. The feet are mesaxonic. The forefoot has 3 main digits, and a smaller one (the fifth) is only used when the tapir is walking on soft ground. The hind feet have 3 digits. All the toes are hoofed. Tapirs have relatively long, laterally compressed skulls with a high braincase and convex profile. The nasal bones are short, arched and freely projecting. The nasal opening is very large.

The dental formula of tapirs is similar to that of the equids: 3/3, 1/1, 4/3-4, and 3/3 for a total of 42-44 teeth. The incisors are chisel-shaped and canines are conical. All cheek teeth lack cement. They are low-crowned and strongly lophodont.

Tapirs have one offspring after a gestation of about 13-14 months. Young of all four species have striped markings which are lost after the first 6 months of life. The young are weaned after 10-12 months, and sexual maturity is reached at about 2-4 years. Tapirs live for approximately 30 years.

Tapirs are exclusively herbivorous, sheltering in thickets by day and emerging at night to feed in bordering areas of grasses or shrubs. They eat the leaves, buds, twigs and fruits of low-growing, terrestrial plants and also consume aquatic vegetation. They are very good swimmers and are fond of splashing in water and wallowing in mud. Tapirs are essentially solitary except for females with offspring.

The earliest records of tapirids in the fossil record are from the Early Oligocene. The Eocene genus Heptodon was remarkably similar to modern tapirs, except that it lacked a proboscis. Tapirs were once widespread in distribution, present in North America, Europe, and Asia until the late Pleistocene.

Tapirs have been extensively hunted for food and sport in some areas, although some Indian tribes refuse to kill tapirs for religious reasons. They have been known to damage corn crops and other grains in Central America, although they are not in general considered a pest species. Populations of all species have declined in recent years because of clearing of forests by humans for agricultural reasons. All species are currently classified by USDI as endangered.

Technical characters

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References and literature cited:

Carter, D.C. 1984. Perissodactyls. Pp. 549-562 in Anderson, S. and J. K. Jones, Jr. (eds). Orders and Families of Recent Mammals of the World. John Wiley and Sons, N.Y. xii+686 pp.

Nowak, R.M. and J.L. Paradiso. 1983. Walker's Mammals of the World, 4th edition. John Hopkins University Press, Baltimore, MD.

Parker, S.P., ed. 1990. Grzimek's Encyclopedia of Mammals, Vol. III. McGraw-Hill Publishing Company, New York.

Savage, R. J. G. and M. R. Long. 1986. Mammal Evolution: An Illustrated Guide. Facts on File Publications, UK. 251 pp.

Wilson, D. E., and D. M. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. 2nd edition. Smithsonian Institution Press, Washington. xviii+1206 pp. 


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Rhinocerotidae

(Rhinoceros)

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The family Rhinoceroteridae contains living rhinoceroses. They are represented by 5 species placed in 4 genera. Three of these species are found in south-central Asia and the other two live in Africa south of the Sahara. Rhinoceroses generally inhabit savannahs, shrubby regions and dense forests, and the African species usually live in more open areas than do the Asiatic species. All rhinos are generally restricted to areas where a daily trip to water is possible.



Species included in the Animal Diversity Web:
  Ceratotherium simum (White Rhinoceros) -pt- 
  Dicerorhinus sumatrensis (Sumatran Rhinoceros) -t- 
  Diceros bicornis (Black Rhinoceros) -pta- 
  Rhinoceros sondaicus (Javan Rhinoceros) -t- 
  Rhinoceros unicornis (Greater Indian Rhinoceros) -pt- 

Accounts marked with a p contain pictures, t contain narrative text (student authored), a contain anatomical still/QTVR images, and s contain digitized sound clips. 

Rhinos have massive bodies and a large head with 1-2 horns. The horns are dermal in origin; they are very solid and are composed of compressed, fibrous keratin. Rhinos have a broad chest and short, stumpy legs. The radius/ulna and tibia/fibula are only slightly moveable, but they are well-developed and separate. Both hind and forefeet are mesaxonic with 3 digits each; each digit with a small hoof. Rhinos have small eyes and fairly short but prominent and erect ears. Their thick skin is scantily-haired and wrinkled, furrowed or pleated, producing the appearance of riveted armor plates in some species. The tail bears stiff bristles.

Rhinos have an elongate skull, which is elevated posteriorly. They have a small braincase, and the nasal bones project forward freely and may extend beyond and above the premaxillae. The surface of the nasals where the horns sit is roughened. There is a strongly developed occipital crest. Rhinos have 24-34 teeth, mostly premolars and molars for grinding (dental formula 1-2/0-1, 0/1-1, 3-4/3-4, 3/3). The canines and incisors are vestigial except for the lower incisors in Asian rhinos, which are developed into powerful slashing tusks. In grazing rhinos (Ceratotherium), the cheek teeth are hypsodont, but they are brachydont in the other genera. Cheek teeth of all species have prominent transverse lophs of enamel.

Female rhinos give birth every 2 years to a single calf, which is active soon after birth and remains with the mother until the next offspring is born. Gestation is 420-570 days. Sexual maturity is reached at 7-10 years for bulls and 4-6 years for cows. The potential lifespan is approximately 50 years.

In general, African rhinos are more aggressive than Asian species. Asian forms fight with their bottom teeth (slashing) whereas African species fight with their horns, using them to toss and gore their adversaries. African rhinos tend to feed low to the ground whereas Asian rhinos usually browse on leaves. Both Asian and African rhinos are more active in the evening, through the night and in early morning, spending their days resting in heavy cover. Members of both groups are herbivores, but they may feed primarily on grasses or on branches, depending on the species. Rhinos sleep in both standing and laying positions and are fond of wallowing in muddy pools and sandy riverbeds. They penetrate dense thickets by shear force, often leaving behind a trail that other animals later use. Rhinos run with a cumbersome motion, reaching top speed at a canter. They can, however, attain speeds of up to 45 km per hour for short distances.

Rhinoceroses are basically solitary and territorial except for the mother-child unit. Groups of adult cows or bachelor bulls are sometimes formed, however, and during the mating season pairs of rhinos may stay together for up to 4 months. Rhinos mark their territories with urine and by dropping their dung in well-defined piles that can reach up to 1 m in height. They often furrow the areas around these piles with their horns, making the piles even more conspicuous.

Fossil rhinos are known from the late Eocene. A closely related family, Hyracodontidae, produced the largest land mammal to have ever lived, Indricotherium. This rhinoceros is believed to have stood 5.4 m tall at the shoulder and to have been capable of reaching vegetation over 8 m above the ground. It probably weighed around 30,000 kg -- over 4 times the weight of a modern elephant. Rhinocerotids were abundant in North America, Europe, and Africa from Miocene through Pleistocene times. Rhino species grazed temperate grasslands and tundra, and many were covered with a thick coat of hair. One of these species, the woolly rhino (Coelodonta), is clearly shown in the cave paintings of early humans.

All species of rhinos are extremely endangered due to overhunting and destruction of their habitat. Humans have hunted rhinos extensively because nearly all parts of the animal have been used in folk medicine. The most prized part of the rhino is its horn, which has been used as an aphrodisiac, fever-reducing drug, dagger handle, and as a potion for detecting poison.

Technical characters

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References and literature cited:

Carter, D.C. 1984. Perissodactyls. Pp. 549-562 in Anderson, S. and J. K. Jones, Jr. (eds). Orders and Families of Recent Mammals of the World. John Wiley and Sons, N.Y. xii+686 pp.

Nowak, R.M. and J.L. Paradiso. 1983. Walker's Mammals of the World, 4th edition. John Hopkins University Press, Baltimore, MD.

Parker, S.P., ed. 1990. Grzimek's Encyclopedia of Mammals, Vol. III. McGraw-Hill Publishing Company, New York.

Savage, R. J. G. and M. R. Long. 1986. Mammal Evolution: An Illustrated Guide. Facts on File Publications, UK. 251 pp.

Wilson, D. E., and D. M. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. 2nd edition. Smithsonian Institution Press, Washington. xviii+1206 pp.