Ungulate

Ungulates are a group of big animals with hooves that include a wide range of species. Horses, rhinoceroses, and tapirs are examples of odd-toed ungulates, while cattle, pigs, giraffes, camels, sheep, deer, and hippopotamuses are examples of even-toed ungulates. Cetaceans are likewise ungulates with even toes, however they don't have hooves. When moving, most terrestrial ungulates rely on the tips of their toes, which are usually hoofed, to support their body weight.

The name basically translates to "being hoofed" or "hoofed animal." Cetaceans (whales, dolphins, and porpoises) are usually excluded from the name "ungulate" since they lack most of the anatomical traits of ungulates, although recent studies suggest that they are descended from early artiodactyls. Ungulates are herbivorous by nature, and many have specific gut bacteria that help them digest cellulose. Modern animals, such as pigs, are omnivorous, whereas prehistoric animals, such as mesonychians, were carnivorous.

History of Ungulate 

Ungulata is a clade (or great order in certain taxonomies) of mammals. The Perissodactyla (odd-toed ungulates) and Artiodactyla (even-toed ungulates) were the two ungulate orders (even-toed ungulates). Hyracoidea (hyraxes), Sirenia (sea cows) (dugongs and manatees), and Proboscidea (elephants) were previously classified with the ungulata in a superorder named Paenungulata. These three orders have been grouped together in the Afrotheria clade, whereas Ungulata has been moved to the Laurasiatheria clade.

Characteristics of Ungulate 

The majority of ungulates lack a collar bone, resulting in considerable variety in response to sexual selection and ecological events. Terrestrial ungulates were mostly herbivores, with a few grazers thrown in for good measure. Pigs, peccaries, hippos, and duikers, on the other hand, were known to eat a wide variety of foods. Baleen whales consume much smaller animals in respect to their body size, such as small species of fish and krill; toothed whales consume a wide range of species, depending on the species: squid, fish, sharks, and other mammals such as seals and other whales.

In terms of ecosystems, ungulates have invaded every part of the globe, from mountains to the deepest parts of the ocean; grasslands to deserts; and some have even been tamed by humans.

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Anatomy of Ungulate 

As we have already discussed ungulate meaning, now let's see the anatomy of ungulate.

Ungulates have evolved unique adaptations, particularly in the areas of cranial appendages, dentition, and leg morphology, which includes the replacement of the astragalus (one of the ankle bones at the end of the lower leg) with a short, robust head.

1. Hooves 

An ungulate mammal's hoof is the tip of its toe, which is protected by a thick horny (keratin) covering. A hard or rubbery sole and a hard wall created by a thick nail rolled around the tip of the toe make up the hoof. Both the sole and the border of the hoof wall generally bear the animal's weight. Hooves are constantly growing and being worn down by use. The radius and ulna are fused down the length of the forelimb in most modern ungulates; early ungulates, such as the arctocyonids, did not have this distinctive skeletal feature. An ungulate's forelimb cannot rotate due to the fusion of the radius and ulna.

While the two orders of ungulates were given their names based on the number of toes on their members ("odd-toed" for perissodactyls and "even-toed" for terrestrial artiodactyls), this was not the most accurate rationale for their classification. Even though tapirs have four toes in the front, they belong to the "odd-toed" order; peccaries and modern cetaceans belong to the "even-toed" order, but peccaries have three toes in the front, and whales have flippers instead of hooves. Scientists have classed them based on how their weight was distributed between their toes.

2. Teeth

Most ungulates have bunodont (low, rounded cusps) and hypsodont (high crowned) teeth, as well as shortened canines and specialised molars. The evolution of hypsodonty has piqued researchers' interest because it was significantly linked to the spread of grasslands throughout the Miocene, some 25 million years ago. As forest biomes dwindled, grasslands expanded, allowing mammals to find new homes. Many ungulates converted from browsing to grazing diets, and hypsodonty became frequent, presumably due to abrasive silica in grass. Recent evidence, on the other hand, links the evolution of hypsodonty to open, rocky settings rather than the grass itself. The concept is known as the Grit, not Grass hypothesis.

3. Cranial Appendages

Ungulates developed a number of cranial appendages that are still found in cervoids today (with the exception of musk deer). The horns of oxen and antelope vary significantly in size and shape, but the basic structure is usually a pair of simple bony protrusions without branches, typically spiral, twisted, or fluted, and each wrapped in a permanent keratin sheath. Bovids are distinguished from other pecorans by their distinct horn structure, which is the single unmistakable physical trait. The development of male horns has been connected to sexual selection, but the existence of horns in females is thought to be the result of natural selection.

Females had smaller horns than males, and their horns were sometimes of a distinct shape. Female bovids' horns are assumed to have developed for defence against predators or to display territoriality, as non territorial females who can use crypsis for predator defence do not usually have horns.

Odd-Toed Ungulates

Odd-toed ungulates are mammals that belong to the biological order Odd-toed ungulates. Perissodactyla are ungulates that have reduced their weight-bearing toes to three (rhinoceroses and tapirs, but tapirs still use four toes on their front legs) or even one (horses, third toe). Non-weight-bearing toes might be present, missing, vestigial, or posteriorly positioned. The even-toed ungulates, on the other hand, bear the majority of their weight evenly on two (an even number) of their five toes: the third and fourth toes.

Odd-toed ungulates digest plant cellulose in their intestines rather than one or more stomach chambers like even-toed ungulates. Equidae (horses, asses, and zebras), Rhinocerotidae (rhinoceroses), and Tapiridae (tapiridae) are the three families that make up the order (tapirs).

Despite their dissimilar appearances, biologist Richard Owen, who also developed the order name, recognised them as related families in the 19th century.

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Scientific Classification

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Clade: Ungulata

Order: Perissodactyla

Anatomy of Odd-toed Ungulates

Rhinoceroses are the largest odd-toed ungulates, and the extinct Paraceratherium, a hornless rhino from the Oligocene, is regarded as one of the world's largest land animals. On the other hand, an early member of the order, the prehistoric horse Eohippus, stood just 30 to 60 cm tall at the withers (12 to 24 in). Perissodactyls, with the exception of dwarf variations of the domestic horse and donkey, have a body length of 180–420 cm (71–165 in) and a weight of 150–4,500 kg (330 to 9,920 lb). Tapirs and horses have dense, short coats, whereas rhinos have sparse hair and a thick skin. The majority of species are grey or brown, with the exception of zebras and young tapirs, which are striped.

1. Limbs 

Both the front and back foot' major axis pass through the third toe, which is always the largest. The size of the remaining toes has been reduced to varied degrees. Tapirs have four toes on their forefeet and three on their hind feet, which allows them to walk on soft ground. Both the front and back feet of living rhinos have three toes. Modern equines have only one toe, but their feet are covered with hooves that almost entirely hide the toe. Rhinos and tapirs, on the other hand, have soft hooves that just cover the leading edge of their toes.

Ungulates must stand on the tips of their toes in certain positions. Equine ungulates with only one digit or hoof have less movement in their limb, which helps them to run quicker and more agilely. The form of the humerus reveals differences in limb structure and physiology between ungulates and other animals. Bones of the largest and heaviest ungulates, such as the Rhinoceros, are frequently shorter and thicker.

2. Skull and Teeth

Odd-toed ungulates have an elongated skull due to their lengthy upper jaw and expanded diastema between the front and cheek teeth. The many types of snouts found in different families are attributable to changes in the shape of the premaxilla. In the eye sockets, the lacrimal bone bears protruding cusps and a wide contact with the nasal bone. The mandible is larger and the temporomandibular joint is elevated.

Rhinos have one or two horns consisting of agglutinated keratin, as opposed to the bone core found in the horns of even-toed ungulates.

3. Gut 

Hindgut fermenters are found in all perissodactyls. In contrast to ruminants, hindgut fermenters keep digested food in an expanded cecum after it has passed through the stomach, where bacteria break down it. There is no gallbladder present. Perissodactyls have a simple stomach, whereas horses have a cecum that may hold up to 90 litres (24 US gal). In horses, the gut can be as long as 26 metres (85 feet). Nutrient extraction from food is inefficient, which explains why no odd-toed ungulates are small; nutritional requirements per unit of body weight are lower for large animals, and the surface-area-to-volume ratio is smaller.

Lifestyle and Diet 

Perissodactyls live in a variety of environments, which leads to a variety of lifestyles. Tapirs are solitary creatures which prefer to live in tropical rainforests. Rhinos like to live alone in dry savannas and wet marsh or woodland environments in Asia. Horses roam in herds and reside in open regions such as grasslands, steppes, and semi-deserts. Odd-toed ungulates are herbivores that eat on grasses, leaves, and other plant parts to varied degrees. Grass-feeding animals (white rhinos, equines) are generally distinguished from leaf-feeding animals (tapirs, other rhinos).

Reproduction and Development 

Odd-toed ungulates have a long gestation period and a small litter size, usually only producing one young. The rhinos have the longest gestation period at 330–500 days. Precocial means that newborn perissodactyls are already quite autonomous when they are born; for example, young horses can begin to follow their mother after only a few hours. The young are nursed for a long time, frequently into their second year, until they attain sexual maturity around the age of eight or ten. Perissodactyls have a lengthy lifespan, with some species, like rhinos, living to be nearly 50 years old in captivity.

Evolutionary History

1. Origin 

Perissodactyla's evolutionary history is well recorded in the fossil record. Numerous discoveries attest to this group's adaptive radiation, which was formerly considerably more diverse and widely scattered. Radinskya, a late Paleocene ungulate from East Asia, is often regarded as one of the ungulates' earliest near relatives. Its 8 cm skull belonged to a small, primitive mammal with a -shaped crown pattern on the enamel of its back teeth, comparable to that of perissodactyls and their cousins, particularly rhinos. Cambaytherium and Kalitherium were discovered in the Cambay shale in western India, indicating that they originated in Asia around 54.5 million years ago.

Their teeth are likewise comparable to those of Radinsky and the Tethytheria clade. The mesaxonic architecture of the front and hind feet, as well as the saddle-shaped navicular joints, indicate a close kinship to Tethytheria. This structure, however, differs from that of Cambaytherium, indicating that it belongs to a sister group. Perissodactyla's ancestors may have arrived on the Indian subcontinent via an island bridge as it moved north towards Asia from the Afro-Arab landmass. Cambaytherium was discovered in India prior to or near its collision with Asia, according to a study.

2. Phylogeny 

In the form of phenacodontids and hyopsodontids, the Perissodactyla arise quite suddenly in the beginning of the Lower Paleocene about 63 million years ago, both in North America and Asia. Sifrhippus, an ancestor of the horses from the Willswood lineup in northwestern Wyoming, is one of the oldest findings from an existing group. Not long later, distant ancestors of tapirs, such as Ganderalophus, Rhinolophus from the Chalicotherium line, or Eotitanops from the brontotheriidae group, arrived in the Ghazij lineup in Balochistan.

Initially, the members of the various lineages appeared to have a similar appearance, with an arched back and four toes on the front and three on the back foot. Outwardly, Eohippus, a member of the horse family, resembled Hyrachyus, the first representative of the rhino and tapir line. All were little in comparison to later species and lived in forests as fruit and foliage eaters. The brontotheres were the first megafauna to appear in the Middle and Upper Eocene. Megacerops was a North American dinosaur that grew to a height of 2.5 metres (8 feet 2 inches) and weighed slightly over 3 tonnes (3.3 short tons)

When dense jungles gave way to steppe at the end of the Eocene, more successful lines of odd-toed ungulates appeared, such as the chalicotheriid rhinos and their immediate cousins; their development likewise began with extremely small forms. During this time, Paraceratherium, one of the world's largest mammals, evolved. They lived during the Oligocene in Eurasia and weighed up to 20 metric tonnes (22 short tonnes). Perissodactyls initially arrived in Africa some 20 million years ago, at the start of the Miocene, when it became connected to Eurasia due to the closing of the Tethys Ocean.

Interaction With Humans 

Domestic horses and donkeys have played a significant role in human history as transportation, labour, and pack animals. Both species were domesticated several millennia before Christ. In Western industrial countries, such use has diminished drastically as a result of the motorisation of agriculture and the spread of automotive traffic; riding is now more commonly done as a pleasure or sport. Traditional usage for these animals are still prevalent in less developed regions of the world. Horses and donkeys are also raised for their meat and milk, albeit to a lesser extent.

Almost all other odd-toed ungulate species, on the other hand, have seen their wild populations plummet as a result of hunting and habitat degradation. The quagga is no longer alive, and Przewalski's horse was once completely extinct in the wild.

According to the International Union for Conservation of Nature (2012), the following are the current threat levels:

• The Javan rhinoceros, Sumatran rhinoceros, black rhinoceros, and African wild ass are all considered severely endangered.

• The mountain tapir, Central American tapir, Malayan tapir, wild horse, and Grévy's zebra are all endangered species.

• The Indian rhinoceros, the South American tapir, and the mole are three endangered species.

• The onager, plains zebra, and white rhinoceros are all near-threatened; however, the northern subspecies of the white rhinoceros, Ceratotherium simum cottoni (northern white rhinoceros), is on the verge of extinction.

• The kiang is not thought to be endangered.

Conclusion

Ungulates are large animals with hooves that come in a variety of species. Odd-toed ungulates include horses, rhinoceroses, and tapirs, while even-toed ungulates include cattle, pigs, giraffes, camels, sheep, deer, and hippopotamuses. Cetaceans are similar to ungulates in that they have even toes but no hooves. When moving, most terrestrial ungulates maintain their body weight on the tips of their toes, which are usually hoofed.

Odd-toed ungulates are mammals that belong to the Odd-toed ungulates biological order. Perissodactyla are ungulates with three (rhinoceroses and tapirs, however tapirs still have four toes on their front legs) or even one weight-bearing toe (horses, third toe). Toes that do not bear weight may be present, absent, vestigial, or positioned posteriorly. Even-toed ungulates, on the other hand, distribute their weight evenly across two (an even number) of their five toes: the third and fourth.