Marsupial

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Marsupial is an inflation member of the mammal Marsupialia . All of the marsupials are endemic in Australasia and America. A typical characteristic common to this species is that most young people are carried in pockets. The famous Marsupials include kangaroos, wallabies, koalas, possums, opossums, wombats, and Tasmanian demons. Some of the lesser known marsupials are potoroo and quokka.

Marsupials represent clades derived from the last ancestors of metheidians that still exist. Like other mammals in Metatheria, they give birth to relatively undeveloped infants who are often in pockets located in their mother's abdomen for a period of time. Almost 70% of the 334 extant species occur in the Australian continent (mainland, Tasmania, New Guinea and nearby islands). The remaining 100 are found in America - mainly in South America, but thirteen in Central America, and one in North America, north of Mexico.

The word marsupial is derived from marsupium , a technical term for the abdominal pouch. This, in turn, was borrowed from Latin and finally from the ancient Greek ????????? , which means "pockets."

Video Marsupial

Taxonomy

Marsupials are taxonomically identified as members of the infant mammals Marsupialia, first described as a family under the command of Pollicata by the German zoologist Johann Karl Wilhelm Illiger in his work in 1811 Prodromus Systematis Mammalium et Avium . However, James Rennie, author of The Natural History of Monkeys, Opossums and Lemurs (1838), points out that the placement of five different groups of mammals - monkeys, lemurs, tarsiers, aye-aye and marsupials (with the exception of kangaroos , placed under the Salientia command) - under one command (Pollicata) does not seem to have strong justification. In 1816, the French zoologist George Cuvier classified all the marsupials under the Marsupialian order. In 1997, researchers J. A. W. Kirsch and others were given infraclass ratings to Marsupialia. There are two main divisions: American marsupial (Ameridelphia) and Australian marsupial (Australidelphia).

Classification

Marsupialia is subdivided as follows:

- Destroyed

• Superorder Ameridelphia
  • Didelphimorphia orders (93 species)
    • The Didelphidae family: opossum
  • Pauciadd infotuberculata messages (seven species)
    • Caenolestidae family: squirrel drizzle
• Superorder Australidelphia
  • Microbiotherapy order (one species)
    • Microbiotherapy family: monito del monte
  • Yalkaparidontia message ( incertae sedis )
  • Dasyuromorphia message (75 species)
    • The Thylacinidae family: thylacine
    • The Dasyuridae family: antechinuses, quolls, dunnarts, Tasmanian devils, and relatives
    • The Myrmecobiidae family: numbat
  • Notoryctemorphia message (two species)
    • Family Notoryctidae: marsupial moles
  • Peramelemorphia messages (24 species)
    • The Thylacomyidae family: bilbies
    • The Chaeropodidae family: pig-legged bandicoot
    • The Peramelidae family: bandicoots and affiliates
  • Protodontion messages (137 species)
    • Family Phascolarctidae: koala
    • The Vombatidae family: wombat
    • Diprotodontidae family: diprotodon
    • Phalangeridae family: poses and brush comb
    • Families of Palorchestidae Tapir Marsupial
    • The Burramyidae family: pygmy position
    • Tarsipedidae family: honey possum
    • The Mapuridae family: striped possum, Leadbeater possum, yellow launcher, sugar glider, mahjong glider, squirrel glider
    • The Pseudocheiridae family: parent bracket and relatives
    • The Potoroidae family: potoroos, rat kangaroos, bettong
    • The Acrobatidae family: glider feathertail and tail feathers
    • Family Hypsiprymnodontidae: musky rat-kangaroo
    • The Macropodidae family: kangaroos, wallabies, and relatives
    • The family of Thylacoleonidae: marsupial lion

Phylogenetic relationships

Consisting of over 300 extant species, several attempts have been made to accurately interpret the phylogenetic relationship between different marsupial orders. The study differs on whether Didelphimorphia or Paucituberculata are sister groups for all other marsupials. Although the order of Microbiotheria (which has only one species, monito del monte) is found in South America, the morphological similarity suggests that it is closely related to Australian marsupials. Molecular analyzes in 2010 and 2011 identified Mikrobiotheria as a sister group for all Australian marsupials. However, the relationship between the four orders of Australidelphid is not well understood. The cladogram below, which illustrates the relationship between the various marsupial commands, is based on phylogenetic studies 2015.

DNA evidence supports the origin of South American marsupials, with Australian marsupials emerging from a single Gondwanan marsupial migration from South America to Australia. There are many small arboreal species in each group. The term "opossum" is used to refer to American species (although "possum" is a common species), whereas a true Australian species is called "possum".

Maps Marsupial

Anatomy

Marsupials are characteristic of mammals - for example, milk glands, three middle ear bones, and genuine hair. Nevertheless, there are striking differences as well as a number of anatomical features that separate them from Eutherians.

In addition to the front pockets, which contain multiple nipples for the protection and food of their children, the marsupial has other common structural features. Scattered patellae is not found in modern marsupials (although a small number of exceptions are reported) and epipubic bone are present. Marsupial (and monotremate) also have no dirty communication (corpus callosum) between right and left brain hemispheres.

Description

Skulls and teeth

The skull has a particularity compared to the higher mammals. In general, the skull is relatively small and tight. The hole ( foramen lacrimale ) is located in the front of the orbit. The cheekbone enlarges and extends farther back. The angular extension ( processus angularis ) of the lower jaw is bent toward the center. Another feature is the hard palate which, unlike the higher mammalian foramina, always has more openings. Teeth differ from placental mammals, so all taxa except wombats have different incisors in the upper and lower jaws. The earliest marsupials have a dental formula of 5/4-1/1-3/3-4/4, that is, per half pine; they had five upper jaws or four mandibular incisors, one canine tooth, three premolar teeth and four molars, totaling 50 teeth. Some taxa, such as opossum, have a number of original teeth. In other groups, the number of teeth decreases. Marsupials in most cases have 40 to 50 teeth, much more than placental mammals. The upper jaw has a high number of incisors, up to ten, and they have more molars than premolars. The second set of teeth grows only in premolar 3: all remaining teeth are already made as permanent teeth.

Torso

Some common characteristics describe their framework. In addition to the details in ankle construction, the bone ( Ossa epubica ) is characteristic, two of the pelvic pubic bone, which is the bone projecting forward. Since it is present in men and species without pockets, it is believed that they originally had nothing to do with reproduction, but were presented in a muscular approach to rear-end movements. The egg-laying platypus has a marsupial bone. This can be explained by the features of the original mammal. The marsupial reproductive organs differ from the higher mammals. For them, the reproductive tract is duplicated. Females have two uteri and two vaginas, and before birth, birth canal forms between them, the median vagina. Men have penis split or doubled in front of the scrotum.

Sacs exist in some but not all species. Some marsupials have a permanent pouch, whereas in others the pouch develops during pregnancy, as in mouse opossum, where the young is only hidden by the skin folds or in the mother's fur. Pocket settings vary to allow children to receive maximum protection. Kangaroo locomotives have pocket openings on the front, while many others that walk or climb crawling have openings in the back. Typically, only females have pockets, but male water opossums have pockets that are used to accommodate his cock while swimming or running.

General and convergence

Marsupials have adapted to many habitats, reflected in various kinds in their building. The largest marsupial giant, red kangaroo, grows up to 1.8 meters (5.9 feet) and 90 kilograms (200 pounds) by weight, but the extinct genera, such as Diprotodon, are significantly larger and heavier. The smallest member of this group is marsupial mice, which often reach only 5 cm (2.0 inches) in body length.

Some species resemble higher mammals and are examples of convergent evolution. The extinct Thylacine is very similar to the placental wolf, hence the nickname "Tasmanian wolf". Flying and related abilities to glide occur both with marsupials (such as with sugar gliders) and some higher mammals (such as with flying squirrels), which are independently developed. Other groups such as kangaroos, however, have no placental partners.

The reproductive system

The marsupial reproductive system is very different from that of placental mammals. During embryonic development, the placenta choriovitelline forms in all marsupials. In bandicoots, an additional chorioallantoic placenta form, although it lacks the chorionic villi found in the eutherian placenta.

The evolution of reproduction in marsupials, and speculation about the ancestral state of mammalian reproduction, has been engaged in discussions since the late 19th century. Both sexes have a cloaca, which is connected to the urogenital sac used to store the waste prior to expulsion. The bladder of the marsupial serves as a place to concentrate urine and boils down to the common urogenital sinuses both in women and men.

Male reproductive system

Most male marsupials, except macropods and marsupial moles, have branched penises, separated into two columns, so the penis has two ends associated with two female vaginas. The penis is used only during copulation, and separated from the urinary tract. Curve forward when erect, and when it is not erect, it is pulled into the body in an S.-shaped curve Both marsupial and monotrem have a baculum. The glans penis shape varies among marsupial species.

The male thylacine has a pouch that acts as a protective sheath, covering the external reproductive organs as it runs through a thick brush.

The urethral groove shape of the male genitalia is used to distinguish between Monodelphis brevicaudata Monodelphis domestica and Monodelphis americana. The grooves form 2 separate channels that form the ventral and dorsal folds of erectile tissue. Some marsupial dasyurid species can also be distinguished by their penis morphology.

The only accessory of the marsupial sex glands is the prostate and bulbourethral glands. There are no ampullae, seminal vesicles or coagulation glands. Prostate is proportionally larger in marsupial than in placental mammals. During the mating season, the male prostate tammar wallaby and bulbourethral gland grow. However, there seems to be no seasonal difference in the weight of the testes.

Female reproductive system

Female mamupials have two lateral vaginas, which cause separate uteri, but both are open externally through the same hole. The third channel, the median vagina, is used for birth. This channel can be temporary or permanent.

Marsupials give birth at an early stage of development; after birth, the newborn marsupials crawl their mother's body and attach themselves to the nipple, located at the bottom of the mother, either in a bag called marsupium, or open to the environment. There they remain for several weeks, attached to the nipple. Her offspring can finally leave marsupium for a short time, returning there for warmth, protection, and food.

Initial development

Early births eliminate growing marsupials from the mother's body faster than in placental mammals, so marsupials do not develop a complex placenta to protect the embryo from its mother's immune system. Although early births place small-born marsupials at greater environmental risk, it significantly reduces the dangers associated with long pregnancies, since there is no need to bring a large fetus to full condition in a bad season. Marsupials are very altricial animals, need to be treated intensively immediately after birth (cf. precocial).

Because newborn marsupials must climb onto their mother's nipples, their front limbs and facial structures are much more developed than the rest of their bodies at birth. This requirement has reasoned to have resulted in the limited reach of locomotor adaptation in marsupials compared with placenta. Marsupials must develop a gripping footing during their youth, making the evolutionary transition from these limbs to nails, wings, or fins, as some groups of placental mammals have done so, more difficult. However, some marsupials have an atypical foot front morphology, such as the legged forelimbs of pig-footed feet, indicating that the range of forelimb specialization is not limited as assumed.

The marsupial baby is known as joey . Marsupials have very short gestation periods (about four to five weeks), and joey is born in a fetal state basically. Blind, furless, miniature baby, the size of a jelly bean, crawling on her mother's fur to get into the bag, where she sticks to the pacifier for food. It will not reappear for several months, during which time it develops completely. After this period, joey begins to spend a long time getting out of the bag, feeding, and learning survival skills. However, he returned to the sleeping bag, and if the danger threatened, he would seek refuge in his parent pouch for salvation.

Joeys lived in pockets for up to a year in some species, or until the next joey was born. A joey marsupial can not regulate its own body temperature and relies on an external heat source. Until the joey is well hairy and old enough to leave the bag, the bag temperature 30-32Ã, Â ° C (86-90Ã, Â ° F) should be kept.

Joeys was born with an "oral shield". In species without bags or with an imperfect pouch this is more developed than in the form with a well-developed pouch, implying a role in maintaining the youth attached to the nipple.

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Interaction with humans

The first American marsupial animals that Europeans encountered were common oposums. Vicente YÃÆ'¡ÃÆ' Â ± ez PinzÃÆ'³n, commander of NiÃÆ' Â ± a on Christopher Columbus's first voyage in the late 1400s, collecting young women's opossums in his pockets off the coast of Brazil. He gave it to the kings of Spain, though by that time the young people had disappeared and the woman had died. The animal is famous for its odd bag or "second stomach", and how the descendants reached the pouch was a mystery.

On the other hand, the Portuguese first described the Australian marsupials. AntÃÆ'³nio GalvÃÆ'Â o o, a Portuguese administrator in Ternate (1536-40), wrote a detailed account of the northern general cuscus (Phalanger orientalis):

Some animals resemble weasels, only slightly larger. They are called Kusus. They have a long tail that they hang from a tree where they live continuously, winding once or twice around the branch. In their stomachs, they have a pocket like a central balcony; as soon as they give birth to the young, they plant it in the nipple until it is no longer necessary to breastfeed. As soon as she gives birth and nurtures her, the mother becomes pregnant again.

From the beginning of the 17th century more stories about marsupials arrived. For example, the records of 1606 animals, who were killed on the southern coast of New Guinea, described it as "in the form of a dog, smaller than a greyhound", with "scaly tail like a snake" and hanging testicles. The meat tasted like venison, and the stomach contained ginger leaves. This description appears very similar to dusky pademelon ( Thylogale brunii ), which in this case is the earliest European record of a member of the kangaroo family (Macropodidae).

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Evolution

The relationship between the three remaining mammalian divisions (monotrem, marsupial, and placenta) has long been debated among taxonomists. Most of the morphological evidence comparing features such as the number and structure of teeth and structures of the reproductive and waste disposal systems and most of the genetic and molecular evidence supports a closer evolutionary relationship between marsupials and placental mammals rather than monotremates.

The marsupial ancestors, part of a larger group called metatherians, may be separated from placental mammals (eutherians) during the mid-Jurassic period, although no fossil evidence from metachians itself is known from this period. From DNA and protein analysis, the divergence time of two lineages is estimated to be about 100 to 120 mya. Metallic fossils are distinguished from eutherians by the shape of their teeth; methers have four pairs of molars in each jaw, whereas eutherian mammals (including the true placenta) have never had more than three pairs. Using this criterion, the earliest known metologist was Sinodelphys szalayi , who lived in China about 125 mya. This makes it contemporary for some of the earliest eutherian species that have been found in the same area. While placental fossils predominate in Asia, marsupial fossils occur in larger numbers in North America.

The oldest methane fossils are found in present-day China. About 100 mya, the supercontinent Pangea is in the process of splitting into the northern continent of Laurasia and the southern continent of Gondwana, with what will be China and Australia separated by the Tethys Ocean. From there, the metropolitan people spread westward to modern North America (still attached to Eurasia), where the earliest true marsupials were found. Marsupials are difficult to distinguish from other fossils, as they are characterized by the usually non-fossilized aspects of the reproductive system (including the pockets) and by the subtle changes in bone and tooth structure that indicate a methane expert is part of the marsupial crown group (the most exclusive group containing all marsupials life). The earliest known marsupial fossil belonging to the Peradectes minor species, from the Paleocene of Montana, dates back about 65 million years ago. From their point of origin in Laurasia, the marsupials spread to South America, which probably connected to North America around 65 mya through a ridge that has since turned into the Caribbean Islands. Marsupial Laurasian eventually died, for not entirely clear reasons; conventions say that they disappear because of competition with the placenta, but this is no longer accepted as the main reason.

Marsurpial, Peradectes and related Herpetotheriidae nest in clade metatherians which also include various North American crater taxis.

In South America, opossums evolved and developed a strong presence, and Paleogen also saw the evolution of squirrel sprigs (Paucituberculata) with non-marsupial methane predators such as borhyaenid and saber teeth Thylacosmilus . The subtleties of South America for mammalian carnivores are dominated by marsupials and sparassodonts. While placenta predators do not exist, meteorologists do have to compete with birds (bird terror) and terrestrial crocodylomorph competitions. South America and Antarctica remain connected to 35 mya, as shown by the unique fossils found there. North and South America broke off until about three million years ago, when the Panama Islands was formed. This leads to the Great American Sisters Intersection. Sparassodonts disappear for no apparent reason - again, it is classically assumed as a competition of the carnivorous placenta, but the latter sparassodonts live together with some small carnivores such as procyonids and canine teeth, and disappear long before the arrival of macropredatory forms such as felines, while didelphimorphs (opossum ) attacked Central America, with Virginia oposum reaching as far north as Canada.

Marsupials reached Australia via Antarctica about 50 mya, shortly after Australia broke away. This shows a single species dispersal event, most likely relative to South American monito del monte (microbiotere, the only australidelphian New World). This ancestor may have crossed a widening gap, but still narrow, between Australia and Antarctica. In Australia, they radiate into the kinds seen today. Modern marsupials seem to have reached the islands in New Guinea and Sulawesi relatively recently through Australia. The 2010 analysis of retroposon insertion sites in various nuclear DNA marsupials has confirmed all living marsupials have a South American ancestor. The bifurcation sequence of the marsupial commands shown by the study puts Didelphimorphia at its most basic position, followed by Paucituberculata, then Microbiotheria, and ends with Australian marsupial radiation. This indicates that Australidelphia appeared in South America, and reached Australia after Microbiotheria split up.

In Australia, terrestrial placental mammals disappear earlier in Cenozoikum (their most recent known fossil is a 55-million-year-old tooth that resembles dental gear) for unclear reasons, allowing marsupials to dominate the Australian ecosystem. Existing Australian terrestrial terrestrial terrestrial mammals (such as jumping mice) are relatively recent immigrants, coming through islands migrating from Southeast Asia.

Genetic analysis shows the date of difference between marsupial and placental on 160 million years ago . The number of ancestral chromosomes has been estimated to be 2n = 14.

Source of the article : Wikipedia