Artiodactyla is an order of mammals in Chordata,[10]Composed of medium to large ungulates.Artiodactyla animals have even numbers of toes on their limbs, which are nearly equal in size, arranged around the axis composed of the highly developed third and fourth toes, and supported by the limb axis above the two toes;The second and fifth toes degenerate, small and backward;Some species grow cave horns or antlers on the frontal bones, canine teeth degenerate in most species with long horns, and are highly developed in species without horns;Having eyelid gland or other exocrine glands is the common feature of this purpose;The bone features include that the talus of the ankle has two pulley shaped surfaces, and the elastic ligaments enable it to walk flexibly and quickly.According to modern molecular analysis, cloven hoofed mammals are closely related to cetaceans, so some classification systems combine them with cetaceans into the same order (Cephalotaxus).[11]
Artiodactyla is widely distributed all over the world except Australia, New Zealand and Antarctica.[12]This order is terrestrial mammals, most of which live in groups. Except for a few omnivores, most of them are herbivores, and run quickly,[13]Social life.[11]
Artiodactyla may originate from an ancient ungulates, ankle arthropods, which have been extinct for a long time. The earliest Artiodactyla was found in the Early Eocene.[14]In the years after the early Eocene, the cloven hoofed animals divided into five large groups, namely Paleodenta, Curved Teeth, Swine, Parapoda and Ruminant.[15]In addition to edible meat, some species of Artiodactyla are valuable medicinal materials, and fur is a good product for leather making and fur clothing;It can also be raised in parks for viewing, and some species can also be domesticated for riding and carrying goods.Most animals have been listed as protected animals, and protection should be strengthened.[13]
Artiodactyla from the 19th centurybritainbiologistRichard Owen (Richard Owen) named it in 1848[1], "Artiodactyla" comes from ancient timesGreek ἄρτιος（ártios, which means "even number") and δ ≤ κτ ν λ ο（dáktylos, meaning "fingers, toes")[4]。
Protection level
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Included in Appendix I, Appendix II and Appendix III of the Convention on International Trade in Endangered Species of Wild Fauna and Flora[9]
Evolutionary history
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Artiodactyla
Articulated hoofed animals arePaleoceneOfCondylarthra Animals evolved from aboutEoceneBegan to differentiate,MioceneandplioceneIs an important period of its evolution.Although there are some successful groups in the early Artiodactyla, they are generally not prosperous. Since MioceneNicheIt is becoming more and more obvious. In modern times, it has an overwhelming absolute advantage, which is far more than other existing ones in terms of variety, quantity and distributionUngulates。
Early cloven hoofed animals resemble modernMurine deer: Small, short legs, feeding on plant stems and leaves.In the late Eocene 46 million years ago, there were four ArtiodactylaSuborderThey have started to differentiate, but they have not occupied the leading ecological positionOdariaIn the boom period of, Artiodactyla can only occupy some marginal niches and reproduce difficultly.However, Artiodactyla began to evolve a complex digestive system at this time, so that it could live on inferior food.
Grass began to appear in Eocene.In Miocene, the global climate became dry with little rainrainforestWither and die,GrasslandIt began to develop and spread to the whole world.Grass itself is a kind of food that is difficult to digest, and Artiodactyla with a complex digestive system can effectively use this crude, low nutrition food.NeogeneLater, cloven hoofed animals replaced the niche of odd hoofed animals and became the main body of herbivores.
Molecular SystematicsResearch shows,CetaceansOriginating from Artiodactyla, it is related to hippopotamusSisterhoodTherefore, the Artiodactyla that does not include whales isDyadic group(i.e. partialEvolutionary branchAre classified into other groups).Based on this, the academic community revised the original classification system and merged Artiodactyla and Cetacea intoMonophylyOfWhale Artiodactyla（Cetartiodactyla）[2]However, when describing non cetacean cloven hoofed animals, the usual name is Artiodactyla.
The latest common ancestor of whales and hippos is a semi aquatic omnivore differentiated from ruminants 59 million years ago. One of them entered the water from South Asia and other places in the Eocene 54 million years ago, and gradually evolved into a completely aquatic whale, which spread to the global sea areas, and some species also entered inland rivers and lakes.In the evolutionary history of species, everythingvertebrateThey all evolved from marine fishes 300 million years ago. The ancestors of whales returned to the ocean 250 million years after leaving the ocean, known as the "second entry", which is a rare major turning event in the history of evolution.
The origin of hippopotamus is not clear, and the earliest knownFossilIs onKenyaThe genus Hippopotamus found in Kenya（Kenyapotamus）They lived in the Miocene between 16 million and 8 million years ago, and there was a 30 million year fossil gap between the differentiation of cetaceans.Occurring in the middle EoceneCarboniferous MammalidaeIt is closely related to hippopotamus, but whether it is the ancestor of hippopotamus has not been recognized.
Subordinate classification
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overview
Artiodactyla
CallopodaWas once regarded asRuminantsBecause they are similar in shape and haveRuminationHabits (although digestive system is different)Molecular scienceOur research shows that callopoda is closer to ArtiodactylaEvolutionary treeIts roots are the first to differentiate among living cloven hoofed animals.The callopods were once very diverse,Zodiaceae, Yuechi VeterinarySisyphodontidaeWhen prehistoric groups are classified here, the only way to reproduce isCamelidae, about 46.2 million years agoEoceneIt originated in North America in the middle period,plioceneSpread to Asia, North Africa and South America, there are 3 genera and 7 species, of which 4 species are domestic animals.
PorciformesThere are two existing ones:old worldOfSwine familyAnd the New WorldTayassuidae 。The suborder was once divided into the lower order of archaodontotes, the lower order of curved odontotes, andSuborder of swine, of which the lower eye of the curved tooth beast is established based on hippos, which containsHippocidaeAnd prehistoricCarboniferous MammalidaeEtc., howeverDNA sequencingIt indicates that hippos and their ancient relatives are closer to whales andRuminantsTherefore, the three sub target classifications are invalid.The typical characteristics of the suborder of swine are short trunk and limbs, large head and long snout, which are suitable for digging underground food;Short tail;Body hair is short and hard, and there areMane；Canine toothDeveloped and lifelong growing, the upper canine teeth of adult males tend to protrude out of the mouth, which is a sharp weapon in fighting.They often roll in muddy water to avoid the invasion of parasites and relieve the heat.
RuminantsWith quite complex digestive system, it is the most evolved terrestrial Artiodactyla, and also the most prosperous category of Artiodactyla. There are six existing families:Tragulidae 、Cervidae、Pronghorn、Deer Family、moschidae 、Bovidae(Holocephalaceae), of which Bovidae is the largest family in Artiodactyla.These families are classified into two suborders: Muricidae is the most basal branch of Ruminants, belonging toMurine Deer Lower Eyes；Other 5 familiesHorny suborderIn the five families, except Musk family, there are two horns on the head, but only male deer family has horns (the only exception isreindeer, both sexes have horns), and only males of some cattle families have horns.
The suborder Whales and Hippocampus includes the suborder Whales and the suborder Dentodontida.There are about 90 species of cetaceans in the suborder Cephalales, which belong to two suborders,Baleen whalesThere are 4 existing families of the order:Right Whale Family, new baleen whale family (or small right whale family)Rorqual 、Eschrichtiidae ；Toothed whales9 families of small orders:Spermatidae, small sperm whales (pygmy sperm whales)Gangetidae(Freshwater Dolphinidae)Ziphiidae (Swordbeaked Whale Family)Subfugu, LafugaceaeDolphinidae、Muscaridae、Monoceratidae(Monoceratidae), another oneMonotypeOfBaiji family, is believed to have become extinct at the beginning of the 21st century.There are only 2 genera and 2 species of Hippocampaceae in the order Hypodentata.
Differentiation relationship in Artiodactyla[5]
list
Note: The list is displayed step by step from Artiodactyla tosectionLevel, section level position undetermined, specific togenusLevel.The list only includes the cloven hoofed species in a narrow sense, but does not show the classification of cetaceans (Cephalopoda).The symbol "†" indicates extinction, and "?" indicates doubt.
The first toe of the order Artiodactyla in modern land is completely degenerated, and only some extinct species have the first toe;The central axis of the four feet passes between the third toe and the fourth toe. These two toes are equally developed and bear the weight evenly in a symmetrical form. They are the most developed toes;The second and fifth toes vary from species to species. The second and fifth toes of hippos are complete in shape and function, supporting the body forward together with the third and fourth toes, while the second and fifth toes of other terrestrial cloven hoofed species are relatively small, hanging behind the feet without touching the ground, having no actual function, and even completely degenerated like the first toe[4]。The front of each toe is covered withsheathShape hooves, with protective effect,PorciformesAnd mostRuminantsTouch the ground with toenail.
Hippopotamus has four toes on each foot, with sound functions
Pigs and most ruminants hang their second and fifth toes behind their feet and land on the ground with their third and fourth toed hooves
The second and fifth toes of camels and a small part of ruminants degenerate, and the toenails are not completely specialized into hooves
Thoracolumbar vertebrae of ArtiodactylaOdariaFew,femurNo "third rotor"[7]。IncisorOnly the mandibular incisors are developed, and the upper incisors are small or degenerated to disappear. They feed only on the upper lip of the hard skin.Anterior molarsandMolarsTectonicHigh crown tooth, with chewing surface suitable for grinding.Such as pigBuccal toothIt has many small tumor like processes, called the mound tooth type;The buccal teeth of ruminant cattle, sheep and deer have extended V-shaped or crescent shaped teeth.
Horny suborderAnimals have two horns on their heads, which can be roughly divided into four types: 1Deer FamilyThe antlers growing in early summer are covered with skin. After ossification, the epidermis is detached and bare. After the breeding period, the antlers fall off in the next spring;twogiraffeIts horn is very short and covered with skin, but its horn and skin never fall off and exist for life;threePronghornThe horn is unbranched, but has a small fork, and the horn sheath falls off every year;fourBovidaeThe horn does not fall off or bifurcate. It is covered with a hard horny sheath. The bone core and horny sheath of the horn grow for life. The horn base of aged animals is thick and the horn trunk is long.
The armpits of some pigsgroinIt has two rows of breasts, while most other Artiodactyla have only one or two pairs of breasts.
Artiodactyla is the most diverse order in mammals. The smallest mouse deer weighs only 4 kg, and the largest blue whale can reach 33 meters long and 190 tons, making it the largest animal in the world[3]。In addition, hippopotamus is the largest one in Artiodactyla except whales, with the maximum weight of more than 3 tons;The giraffe is the tallest animal in existence, and its head can be more than 5 meters from the ground.
For the morphological characteristics of cetaceans, see also the subject“Cetaceans”。
digestive system
RuminantsAnd callopoda camelsRestoring stomach, all have ruminant characteristics.becausePlant fibreIt is difficult to digest, and the process of feeding is usually in a hurry. Most food is swallowed without sufficient chewing. Therefore, rumination is a special function evolved to shorten the feeding time and strengthen the digestion of coarse food.
The stomach of Ruminants is divided into four chambers:rumen(There are many on the inner walltumourProtuberance)Reticulum(also known as the honeycomb stomach, the inner wall has mesh like folds similar to the honeycomb)Omasum stomach(also known as the double flap stomach, with many overlapping leaf flaps of different sizes on the inner wall)abomasum(also known as true stomach, with many folds on the inner wall), none of the first three ventriclesgastric glandThe overall function is to ferment, filter, grind and roughly absorb the nutrients of food. Only the abomasum is secretedDigestive juicePart of, equivalent toMonogastric animalStomach.There is also a vestibule in the rumen, which is sometimes regarded as an independent stomach chamber. Some scholars also combine the rumen and reticulum into one unit, so according to different data sourcesRuminantsThere are four to five stomach chambers.Camel stomach is divided into three chambers, and the omasum and abomasum are combined into one.PorciformesAnd the stomach of the suborder Whale Hippo also has multiple chambers (details vary by species), but does not ruminate.
Stomach of Ruminant (arrow indicates the direction of food flow)[8]
RuminantsWhen eating, only chew the food roughly and swallow it.Food arrives at the rumen through the vestibule of the rumen. After being softened and decomposed by rumen microorganisms, it becomes semi digested pulp, which is constantly passed from the rumen to the reticulum, and is constantly ground and mixed in the process.Through the reverse peristalsis between the rumen vestibule and the reticulum, a small part of the food slurry returns to the mouth for careful chewing after reverse emesis, and again mixes with saliva to swallow into the rumen.The slurry can be directly regurgitated from the rumen to the mouth, or it can enter the reticulum from the rumen first, and then return to the mouth from the reticulum, and be chewed carefully before being swallowed into the rumen;This process can be repeated many times until the food is thoroughly chewed, and then from the rumen to the omasum through the reticulum.The reticulum has the function of "filtering". The coarse food stays in the reticulum and the fine food enters the omasum.There are many parallel leaves on the inner wall of the omasumLouver）These leaves crush and grind the food into finer piecesChymeAnd absorb some water and low-gradefatty acidFinally, the thickened food paste is put into the abomasum for digestion, and these digestive products willsmall intestineIs absorbed in.
Growth and reproduction
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Artiodactylathe temperate zoneandFrigid zoneThe species in the area have a fixed breeding season,tropicThe species in the area reproduce throughout the year.Many Artiodactyla practice“Polygamy”That is to say, the male will fight out a single winner and get the right to mate with all females within a certain range.
ArtiodactylaPregnancyGenerally, they are longer and produce fewer cubs.The gestation period of small ruminants and pigs varies from 4 to 5 months;6 to 10 months for medium-sized and large deer, cattle and hippopotamus;10-13 months for camels;Giraffes are 14-15 months old.Most pigs give birth to 1-2 piglets per litter, and a small number of pigs can give birth to more than 10 piglets per litter, which is the largest number of piglets in Artiodactyla.
Artiodactyla larvae are highly developed. They can open their eyes at birth, and their limbs are fully functional. They can learn to run and integrate into the group in a short time.
The natural life span of most Artiodactylas is 20-30 years;Like many mammals, larger species have a longer life span, and vice versa.Among the land cloven hoofed animals, hippos, cows and camels have the longest life span of 40-50 years, while large whales can live for more than 100 years.
Value function
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Artiodactyla is of great value to human beingsAnimal HusbandryandAgricultureAs an important part of, it has been the main source of meat, milk and fur products for tens of thousands of years, and is also widely used in servitude and entertainment activities.
In prehistoric times, humans hunted them for meat and fur, and used their bones and teeth as weapons or tools.Around 8000 BC, Artiodactyla began to be domesticated, which was one of the earliest domesticated animal families of human beings. At firstproteinThe source was eaten, and it was used as a slave to assist human work since about 3000 BC.Artiodactyla exists in almost all human civilizations in the world, such asold worldCattle, sheep, pigs and camels in various civilizations, South AmericaIndianCamels and alpacas in civilization.
