|image from top to left: Giraffe, Plains bison, Dromedary camel, Red deer, Wild boar, Killer whale (Cetacea), Plains zebra, Indian rhinoceros, and Brazilian tapir.|
|Orders and Clades|
Ungulates (pronounced // UNG-gyə-layts) are members of an oul' diverse clade of primarily large mammals with hooves. Story? These include odd-toed ungulates such as horses, rhinoceroses and tapirs, and even-toed ungulates such as cattle, pigs, giraffes, camels, sheep, deer, and hippopotamuses. Jaykers! Cetaceans are also even-toed ungulates, although they do not have hooves, would ye swally that? Most terrestrial ungulates use the bleedin' tips of their toes, usually hoofed, to support their body weight while movin'.
The term means, roughly, "bein' hoofed" or "hoofed animal". Chrisht Almighty. As a descriptive term, "ungulate" normally excludes cetaceans (whales, dolphins, porpoises), as they do not possess most of the oul' typical morphological characteristics of ungulates, but recent discoveries indicate that they were descended from early artiodactyls. Ungulates are typically herbivorous and many employ specialized gut bacteria to allow them to digest cellulose, begorrah. Some modern species, such as pigs, are omnivorous, while some prehistoric species, such as mesonychians, were carnivorous.
Ungulata is a clade (or in some taxonomies, a bleedin' grand order) of mammals. The two orders of ungulates were the feckin' Perissodactyla (odd-toed ungulates) and Artiodactyla (even-toed ungulates). Sufferin' Jaysus. Hyracoidea (hyraxes), Sirenia (sea cows) (dugongs and manatees) and Proboscidea (elephants) were in the oul' past included in a feckin' superorder called Paenungulata which was grouped with the oul' ungulata. These three orders were now considered an oul' clade and grouped in the bleedin' Afrotheria clade while Ungulata is now grouped under the bleedin' Laurasiatheria clade.
In 2009 morphological and molecular work found that aardvarks, hyraxes, sea cows, and elephants were more closely related to each other and to sengis, tenrecs, and golden moles than to the oul' perissodactyls and artiodactyls, and form the feckin' clade Afrotheria, what? Elephants, sea cows, and hyraxes were grouped together in the feckin' clade Paenungulata, while the oul' aardvark has been considered as either a holy close relative to them or a feckin' close relative to sengis in the clade Afroinsectiphilia. This is a bleedin' strikin' example of convergent evolution.
There is now some dispute as to whether this smaller Ungulata is a cladistic (evolution-based) group, or merely a phenetic group (form taxon) or folk taxon (similar, but not necessarily related). G'wan now. Some studies have indeed found the oul' mesaxonian ungulates and paraxonian ungulates to form a feckin' monophyletic lineage, closely related to either the oul' Ferae (the carnivorans and the oul' pangolins) in the feckin' clade Fereuungulata or to the oul' bats. Other studies found the oul' two orders not that closely related, as some place the oul' perissodactyls as close relatives to bats and Ferae in Pegasoferae and others place the artiodactyls as close relatives to bats.
Below is a bleedin' simplified taxonomy (assumin' that ungulates do indeed form a natural groupin') with the feckin' extant families, in order of the oul' relationships. Keep in mind that there were still some grey areas of conflict, such as the feckin' case with relationship of the oul' pecoran families and the oul' baleen whale families. Jaysis. See each family for the relationships of the oul' species as well as the bleedin' controversies in their respective article.
- Ungulata (= Euungulata)
- Perissodactyla (Mesaxonian ungulates)
- Artiodactyla (= Cetartiodactyla) (Paraxonian ungulates)
- Camelidae: Camels and Llamas
- Hippopotamidae: Hippopotamuses
- Platanistidae: Indian river dolphins
- Ziphiidae: Beaked whales
- Lipotidae: Baiji (functionally extinct)
Perissodactyla and Artiodactyla include the feckin' majority of large land mammals, would ye swally that? These two groups first appeared durin' the bleedin' late Paleocene, rapidly spreadin' to a wide variety of species on numerous continents, and have developed in parallel since that time. Some scientists believed that modern ungulates were descended from an evolutionary grade of mammals known as the bleedin' condylarths; the oul' earliest known member of the group was the feckin' tiny Protungulatum, an ungulate that co-existed with the last of non-avian dinosaurs 66 million years ago; however, many authorities do not consider it a true placental, let alone an ungulate. The enigmatic dinoceratans were among the bleedin' first large herbivorous mammals, although their exact relationship with other mammals is still debated with one of the bleedin' theories bein' that they might just be distant relatives to livin' ungulates; the feckin' most recent study recovers them as within the bleedin' true ungulate assemblage, closest to Carodnia.
Perissodactyls were said to have evolved from the bleedin' Phenacodontidae, small, sheep-sized animals that were already showin' signs of anatomical features that their descendants would inherit (the reduction of digit I and V for example). By the feckin' start of the feckin' Eocene, 55 million years ago (Mya), they had diversified and spread out to occupy several continents, fair play. Horses and tapirs both evolved in North America; rhinoceroses appear to have developed in Asia from tapir-like animals and then colonised the bleedin' Americas durin' the feckin' middle Eocene (about 45 Mya). Sure this is it. Of the bleedin' approximately 15 families, only three survive (McKenna and Bell, 1997; Hooker, 2005). C'mere til I tell ya now. These families were very diverse in form and size; they included the enormous brontotheres and the bleedin' bizarre chalicotheres. The largest perissodactyl, an Asian rhinoceros called Paraceratherium, reached 15 tonnes (17 tons), more than twice the weight of an elephant.
It has been found in a bleedin' cladistic study that the anthracobunids and the oul' desmostylians - two lineages that have been previously classified as Afrotherians (more specifically closer to elephants) - have been classified as an oul' clade that is closely related to the bleedin' perissodactyls. The desmostylians were large amphibious quadrupeds with massive limbs and an oul' short tail. They grew to 1.8 metres (6 ft) in length and were thought to have weighed more than 200 kilograms (440 lb), like. Their fossils were known from the feckin' northern Pacific Rim, from southern Japan through Russia, the bleedin' Aleutian Islands and the Pacific coast of North America to the bleedin' southern tip of Baja California. In fairness now. Their dental and skeletal form suggests desmostylians were aquatic herbivores dependent on littoral habitats. Would ye believe this shite?Their name refers to their highly distinctive molars, in which each cusp was modified into hollow columns, so that a bleedin' typical molar would have resembled a feckin' cluster of pipes, or in the case of worn molars, volcanoes. Would ye believe this shite?They were the bleedin' only marine mammals to have gone extinct.
The South American meridiungulates contain the bleedin' somewhat tapir-like pyrotheres and astrapotheres, the feckin' mesaxonic litopterns and the diverse notoungulates. Bejaysus here's a quare one right here now. As a holy whole, meridiungulates were said to have evolved from animals like Hyopsodus. For a bleedin' while their relationships with other ungulates were a holy mystery. Some paleontologists have even challenged the monophyly of Meridiungulata by suggestin' that the oul' pyrotheres may be more closely related to other mammals, such as Embrithopoda (an African order that were related to elephants) than to other South American ungulates. A recent study based on bone collagen has found that at least litopterns and the oul' notoungulates were closely related to the perissodactyls.
The oldest known fossils assigned to Equidae date from the feckin' early Eocene, 54 million years ago. Me head is hurtin' with all this raidin'. They had been assigned to the bleedin' genus Hyracotherium, but the type species of that genus is now considered not a member of this family, but the bleedin' other species have been split off into different genera, the cute hoor. These early Equidae were fox-sized animals with three toes on the feckin' hind feet, and four on the bleedin' front feet, bejaysus. They were herbivorous browsers on relatively soft plants, and already adapted for runnin'. C'mere til I tell yiz. The complexity of their brains suggest that they already were alert and intelligent animals. Later species reduced the bleedin' number of toes, and developed teeth more suited for grindin' up grasses and other tough plant food.
Rhinocerotoids diverged from other perissodactyls by the feckin' early Eocene. Fossils of Hyrachyus eximus found in North America date to this period. Jaysis. This small hornless ancestor resembled an oul' tapir or small horse more than an oul' rhino. Three families, sometimes grouped together as the feckin' superfamily Rhinocerotoidea, evolved in the feckin' late Eocene: Hyracodontidae, Amynodontidae and Rhinocerotidae, thus creatin' an explosion of diversity unmatched for an oul' while until environmental changes drastically eliminated several species.
The first tapirids, such as Heptodon, appeared in the oul' early Eocene. They appeared very similar to modern forms, but were about half the oul' size, and lacked the bleedin' proboscis, to be sure. The first true tapirs appeared in the feckin' Oligocene. Whisht now. By the Miocene, such genera as Miotapirus were almost indistinguishable from the bleedin' extant species. Asian and American tapirs were believed to have diverged around 20 to 30 million years ago; and tapirs migrated from North America to South America around 3 million years ago, as part of the bleedin' Great American Interchange.
Perissodactyls were the dominant group of large terrestrial browsers right through the bleedin' Oligocene. G'wan now. However, the feckin' rise of grasses in the feckin' Miocene (about 20 Mya) saw a feckin' major change: the feckin' artiodactyl species with their more complex stomachs were better able to adapt to a feckin' coarse, low-nutrition diet, and soon rose to prominence. Right so. Nevertheless, many perissodactyl species survived and prospered until the bleedin' late Pleistocene (about 10,000 years ago) when they faced the pressure of human huntin' and habitat change.
The artiodactyls were thought to have evolved from a small group of condylarths, Arctocyonidae, which were unspecialized, superficially raccoon-like to bear-like omnivores from the feckin' Early Paleocene (about 65 to 60 million years ago). They had relatively short limbs lackin' specializations associated with their relatives (e.g. Jesus, Mary and Joseph. reduced side digits, fused bones, and hooves), and long, heavy tails. Jesus, Mary and holy Saint Joseph. Their primitive anatomy makes it unlikely that they were able to run down prey, but with their powerful proportions, claws, and long canines, they may have been able to overpower smaller animals in surprise attacks. Evidently these mammals soon evolved into two separate lineages: the mesonychians and the bleedin' artiodactyls.
Mesonychians were depicted as "wolves on hooves" and were the feckin' first major mammalian predators, appearin' in the feckin' Paleocene. Early mesonychids had five digits on their feet, which probably rested flat on the bleedin' ground durin' walkin' (plantigrade locomotion), but later mesonychids had four digits that ended in tiny hooves on all of their toes and were increasingly well adapted to runnin', like. Like runnin' members of the oul' even-toed ungulates, mesonychids (Pachyaena, for example) walked on their digits (digitigrade locomotion). Mesonychians fared very poorly at the feckin' close of the feckin' Eocene epoch, with only one genus, Mongolestes, survivin' into the feckin' Early Oligocene epoch, as the feckin' climate changed and fierce competition arose from the oul' better adapted creodonts.
The first artiodactyls looked like today's chevrotains or pigs: small, short-legged creatures that ate leaves and the feckin' soft parts of plants. G'wan now and listen to this wan. By the oul' Late Eocene (46 million years ago), the oul' three modern suborders had already developed: Suina (the pig group); Tylopoda (the camel group); and Ruminantia (the goat and cattle group). Whisht now and eist liom. Nevertheless, artiodactyls were far from dominant at that time: the bleedin' perissodactyls were much more successful and far more numerous, would ye swally that? Artiodactyls survived in niche roles, usually occupyin' marginal habitats, and it is presumably at that time that they developed their complex digestive systems, which allowed them to survive on lower-grade food. While most artiodactyls were takin' over the feckin' niches left behind by several extinct perissodactyls, one lineage of artiodactyls began to venture out into the oul' seas.
The traditional theory of cetacean evolution was that cetaceans were related to the bleedin' mesonychids. Arra' would ye listen to this shite? These animals had unusual triangular teeth very similar to those of primitive cetaceans. This is why scientists long believed that cetaceans evolved from a holy form of mesonychid. Today, many scientists believe cetaceans evolved from the same stock that gave rise to hippopotamuses. This hypothesized ancestral group likely split into two branches around . One branch would evolve into cetaceans, possibly beginnin' about with the bleedin' proto-whale Pakicetus and other early cetacean ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the feckin' completely aquatic cetaceans. The other branch became the feckin' anthracotheres, a feckin' large family of four-legged beasts, the bleedin' earliest of whom in the bleedin' late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads. Jesus, Mary and Joseph. All branches of the bleedin' anthracotheres, except that which evolved into Hippopotamidae, became extinct durin' the Pliocene without leavin' any descendants.
The family Raoellidae is said to be the feckin' closest artiodactyl family to the oul' cetaceans. Consequentially, new theories in cetacean evolution hypothesize that whales and their ancestors escaped predation, not competition, by shlowly adaptin' to the oul' ocean.
Ungulates were in high diversity in response to sexual selection and ecological events; the oul' majority of ungulates lack an oul' collar bone. Terrestrial ungulates were for the bleedin' most part herbivores, with some of them bein' grazers, the shitehawk. However, there were exceptions to this as pigs, peccaries, hippos and duikers were known to have an omnivorous diet. Jasus. Some cetaceans were the only modern ungulates that were carnivores; baleen whales consume significantly smaller animals in relation to their body size, such as small species of fish and krill; toothed whales, dependin' on the oul' species, can consume a wide range of species: squid, fish, sharks, and other species of mammals such as seals and other whales. In fairness now. In terms of ecosystem ungulates have colonized all corners of the planet, from mountains to the bleedin' ocean depths; grasslands to deserts and some have been domesticated by humans.
Ungulates have developed specialized adaptations, especially in the feckin' areas of cranial appendages, dentition, and leg morphology includin' the oul' modification of the oul' astragalus (one of the feckin' ankle bones at the oul' end of the lower leg) with a holy short, robust head.
The hoof is the bleedin' tip of an oul' toe of an ungulate mammal, strengthened by a thick horny (keratin) coverin'. The hoof consists of a bleedin' hard or rubbery sole, and an oul' hard wall formed by a holy thick nail rolled around the oul' tip of the bleedin' toe, you know yerself. The weight of the bleedin' animal is normally borne by both the sole and the feckin' edge of the oul' hoof wall. In fairness now. Hooves grow continuously, and were constantly worn down by use, enda story. In most modern ungulates, the oul' radius and ulna were fused along the feckin' length of the forelimb; early ungulates, such as the arctocyonids, did not share this unique skeletal structure. The fusion of the oul' radius and ulna prevents an ungulate from rotatin' its forelimb, to be sure. Since this skeletal structure has no specific function in ungulates, it is considered a holy homologous characteristic that ungulates share with other mammals. This trait would have been passed down from a bleedin' common ancestor. While the bleedin' two orders of ungulates colloquial names were based on the oul' number of toes of their members ("odd-toed" for the bleedin' perissodactyls and "even-toed" for the terrestrial artiodactyls), it is not an accurate reason they were grouped. Bejaysus here's a quare one right here now. Tapirs have four toes in the oul' front, yet they were members of the feckin' "odd-toed" order; peccaries and modern cetaceans were members of the oul' "even-toed" order, yet peccaries have three toes in the bleedin' front and whales were an extreme example as they have flippers instead of hooves. Whisht now and eist liom. Scientists had classified them accordin' to the feckin' distribution of their weight to their toes.
Perissodactyls have a mesaxonic foot meanin' that the bleedin' weight is distributed on the third toe on all legs thanks to the oul' plane symmetry of their feet. There has been reduction of toes from the common ancestor, with the bleedin' classic example bein' horses with their single hooves. C'mere til I tell yiz. In consequence, there was an alternative name for the perissodactyls the feckin' nearly obsolete Mesaxonia. Perissodactyls were not the oul' only lineage of mammals to have evolved this trait; the bleedin' meridiungulates have evolved mesaxonic feet numerous times.
Terrestrial artiodactyls have a feckin' paraxonic foot meanin' that the feckin' weight is distributed on the feckin' third and the oul' fourth toe on all legs. Jesus, Mary and Joseph. The majority of these mammals have cloven hooves, with two smaller ones known as the feckin' dewclaws that were located further up on the leg. Soft oul' day. The earliest cetaceans (the archaeocetes), also have this characteristic in the feckin' addition of also havin' both an astragalus and cuboid bone in the oul' ankle, which were further diagnostic traits of artiodactyls.
In modern cetaceans, the front limbs have become pectoral fins and the feckin' hind parts were internal and reduced. Would ye believe this shite?Occasionally, the genes that code for longer extremities cause a modern cetacean to develop miniature legs (known as atavism). Listen up now to this fierce wan. The main method of movin' is an up-and-down motion with the feckin' tail fin, called the fluke, which is used for propulsion, while the pectoral fins together with the feckin' entire tail section provide directional control. Bejaysus this is a quare tale altogether. All modern cetaceans still retain their digits despite the bleedin' external appearance suggestin' otherwise.
Most ungulates have developed reduced canine teeth and specialized molars, includin' bunodont (low, rounded cusps) and hypsodont (high crowned) teeth. The development of hypsodonty has been of particular interest as this adaptation was strongly associated with the oul' spread of grasslands durin' the oul' Miocene about 25 million years. Jesus Mother of Chrisht almighty. As forest biomes declined, grasslands spread, openin' new niches for mammals. G'wan now and listen to this wan. Many ungulates switched from browsin' diets to grazin' diets, and possibly driven by abrasive silica in grass, hypsodonty became common. C'mere til I tell ya. However, recent evidence ties the oul' evolution of hypsodonty to open, gritty habitats and not the oul' grass itself. This is termed the Grit, not grass hypothesis.
Some ungulates completely lack upper incisors and instead have a bleedin' dental pad to assist in browsin'. It can be found in camels, ruminants, and some toothed whales; modern baleen whales were remarkable in that they have baleen instead to filter out the bleedin' krill from the feckin' water. Be the hokey here's a quare wan. On the oul' other spectrum teeth have been evolved as weapons or sexual display seen in pigs and peccaries, some species of deer, musk deer, hippopotamuses, beaked whales and the bleedin' Narwhal, with its long canine tooth.
Ungulates evolved an oul' variety of cranial appendages that today can be found in cervoids (with the oul' exception of musk deer). Holy blatherin' Joseph, listen to this. In oxen and antelope, the oul' size and shape of the feckin' horns vary greatly, but the oul' basic structure is always a bleedin' pair of simple bony protrusions without branches, often havin' a holy spiral, twisted or fluted form, each covered in a permanent sheath of keratin. The unique horn structure is the bleedin' only unambiguous morphological feature of bovids that distinguishes them from other pecorans. Male horn development has been linked to sexual selection, while the bleedin' presence of horns in females is likely due to natural selection. The horns of females were usually smaller than those of males, and were sometimes of a feckin' different shape. The horns of female bovids were thought to have evolved for defense against predators or to express territoriality, as nonterritorial females, which were able to use crypsis for predator defense, often do not have horns.
Rhinoceros horns, unlike those of other horned mammals, only consist of keratin, the shitehawk. The horns rest on the bleedin' nasal ridge of the feckin' animals skull.
Antlers were unique to cervids and found mostly on males: only caribou and reindeer have antlers on the feckin' females, and these were normally smaller than those of the oul' males. Jaykers! Nevertheless, fertile does from other species of deer have the capacity to produce antlers on occasion, usually due to increased testosterone levels. Each antler grows from an attachment point on the oul' skull called a holy pedicle, fair play. While an antler is growin', it is covered with highly vascular skin called velvet, which supplies oxygen and nutrients to the feckin' growin' bone. Antlers were considered one of the oul' most exaggerated cases of male secondary sexual traits in the feckin' animal kingdom, and grow faster than any other mammal bone. Growth occurs at the tip, and is initially cartilage, which is mineralized to become bone, begorrah. Once the antler has achieved its full size, the bleedin' velvet is lost and the feckin' antler's bone dies. This dead bone structure is the oul' mature antler, begorrah. In most cases, the bone at the base is destroyed by osteoclasts and the bleedin' antlers fall off at some point. As a holy result of their fast growth rate, antlers were considered a handicap since there is an incredible nutritional demand on deer to re-grow antlers annually, and thus can be honest signals of metabolic efficiency and food gatherin' capability.
Ossicones were horn-like (or antler-like) protuberances that can be found on the heads of giraffes and male okapis today. Here's a quare one. They were similar to the oul' horns of antelopes and cattle, save that they were derived from ossified cartilage, and that the oul' ossicones remain covered in skin and fur, rather than horn. Antlers (such as on deer) were derived from bone tissue: when mature, the bleedin' skin and fur coverin' of the bleedin' antlers, termed "velvet", is shloughed and scraped off to expose the bleedin' bone of the oul' antlers.
Pronghorn were unique when compared to their relatives. Each "horn" of the pronghorn is composed of an oul' shlender, laterally flattened blade of bone that grows from the oul' frontal bones of the skull, formin' a permanent core. Jesus, Mary and Joseph. As in the Giraffidae, skin covers the feckin' bony cores, but in the bleedin' pronghorn it develops into an oul' keratinous sheath which is shed and regrown on an annual basis, for the craic. Unlike the feckin' horns of the family Bovidae, the oul' horn sheaths of the bleedin' pronghorn were branched, each sheath possessin' a forward-pointin' tine (hence the feckin' name pronghorn). Jaysis. The horns of males were well developed.
- Cooper, L, would ye believe it? N.; Seiffert, E, to be sure. R.; Clementz, M.; Madar, S. I.; Bajpai, S.; Hussain, S, be the hokey! T.; Thewissen, J, would ye believe it? G. Bejaysus. M. Jaykers! (2014-10-08), fair play. "Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls". PLOS ONE. 9 (10): e109232, fair play. doi:10.1371/journal.pone.0109232. PMC 4189980. Me head is hurtin' with all this raidin'. PMID 25295875.
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- Burger, Benjamin J. (15 October 2015). The Systematic Position of the oul' Saber-Toothed and Horned Giants of the bleedin' Eocene: The Uintatheres (Order Dinocerata) (PDF), like. Society of Vertebrate Paleontology 75th Annual Meetin'. Dallas. Retrieved 20 February 2020. Conference abstract (p. Jesus Mother of Chrisht almighty. 99), the hoor. Explanation and conclusions: on YouTube.
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