Marsupial
Overview
Marsupials are an infraclass
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

 of mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

, and nearby islands, with the remaining 100 found in the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

, primarily in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

, but with thirteen in Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

, and one in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, north of Mexico.
The relationships between the three extant divisions of mammals (monotreme
Monotreme
Monotremes are mammals that lay eggs instead of giving birth to live young like marsupials and placental mammals...

s, marsupials, and placental mammals) was long a matter of debate among taxonomists
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

.
Encyclopedia
Marsupials are an infraclass
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

 of mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

, and nearby islands, with the remaining 100 found in the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

, primarily in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

, but with thirteen in Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

, and one in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, north of Mexico.

History

The relationships between the three extant divisions of mammals (monotreme
Monotreme
Monotremes are mammals that lay eggs instead of giving birth to live young like marsupials and placental mammals...

s, marsupials, and placental mammals) was long a matter of debate among taxonomists
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

. Most morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

 evidence comparing traits such as number and arrangement of teeth
Dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...

 and structure of the reproductive and waste elimination systems
Genitourinary system
In anatomy, the genitourinary system or urogenital system is the organ system of the reproductive organs and the urinary system. These are grouped together because of their proximity to each other, their common embryological origin and the use of common pathways, like the male urethra...

 favors a closer evolutionary relationship between marsupials and placental mammals than either with the monotremes. Most genetic and molecular
Molecular clock
The molecular clock is a technique in molecular evolution that uses fossil constraints and rates of molecular change to deduce the time in geologic history when two species or other taxa diverged. It is used to estimate the time of occurrence of events called speciation or radiation...

 evidence also supports grouping marsupials and placental mammals as a single clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

, subclass Theria
Theria
Theria is a subclass of mammals that give birth to live young without using a shelled egg, including both eutherians and metatherians . The only omitted extant mammal group is the egg-laying monotremes....

.

Marsupials and placental mammals split from the monotremes during the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 Period. In the absence of soft tissues, such as the pouch and reproductive system, fossil marsupials can be distinguished from placentals by the form of their teeth; primitive marsupials possess four pairs of molar teeth in each jaw, whereas placental mammals never have more than three pairs. Using this criterion, the earliest known marsupial is Sinodelphys szalayi
Sinodelphys
Sinodelphys is an extinct mammal from the Early Cretaceous. To date, it is the oldest metatherian fossil known, estimated to be 125 million years old...

, which lived in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 around 125 million years ago (mya). This makes it almost contemporary to the earliest eutherian fossils
Eomaia
Eomaia is an extinct fossil mammal, discovered in rocks that were found in the Yixian Formation, Liaoning Province, China, and dated to the Barremian Age of the Lower Cretaceous about . The fossil is in length and virtually complete. An estimate of the body weight is between . It is exceptionally...

, which have been found in the same area.

The oldest metatherian fossils
Sinodelphys
Sinodelphys is an extinct mammal from the Early Cretaceous. To date, it is the oldest metatherian fossil known, estimated to be 125 million years old...

 (Metatheria
Metatheria
Metatheria is a grouping within the animal class Mammalia. First proposed by Thomas Henry Huxley in 1880, it is nearly synonymous with the earlier taxon Marsupialia though it is slightly wider since it also contains the nearest fossil relatives of marsupial mammals.The earliest known...

 being a larger clade that groups marsupials with some of their extinct relatives) are found in present-day China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

, and there are a few species of marsupials presently living in Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

 as far west as Sulawesi
Sulawesi
Sulawesi is one of the four larger Sunda Islands of Indonesia and is situated between Borneo and the Maluku Islands. In Indonesia, only Sumatra, Borneo, and Papua are larger in territory, and only Java and Sumatra have larger Indonesian populations.- Etymology :The Portuguese were the first to...

, which is sometimes considered to be in an Asian ecozone. However, these modern marsupials appear to be have reached the islands relatively recently via Australia. About 100 mya, the supercontinent Pangaea
Pangaea
Pangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....

 was in the process of splitting into the northern continent Laurasia
Laurasia
In paleogeography, Laurasia was the northernmost of two supercontinents that formed part of the Pangaea supercontinent from approximately...

 and the southern continent Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...

, with what would become China and Australia already separated by the Tethys Ocean
Tethys Ocean
The Tethys Ocean was an ocean that existed between the continents of Gondwana and Laurasia during the Mesozoic era before the opening of the Indian Ocean.-Modern theory:...

. Marsupials spread westward into modern North America (still attached to Eurasia) and then to South America, which was connected to North America until around 65 mya. Laurasian marsupials eventually died off, possibly due to competition from placental mammals for their ecological niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

s.

In South America, the opossums
Didelphimorphia
Opossums make up the largest order of marsupials in the Western Hemisphere, including 103 or more species in 19 genera. They are also commonly called possums, though that term technically refers to Australian fauna of the suborder Phalangeriformes. The Virginia opossum was the first animal to be...

 retained a strong presence, and the Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

 saw the evolution of shrew opossum
Shrew opossum
The order Paucituberculata contains the six surviving species of shrew opossum: small, shrew-like marsupials which are confined to the Andes mountains of South America. It is thought that the order diverged from the ancestral marsupial line very early. As recently as 20 million years ago, there...

s (Paucituberculata) and metatherian predators such as the borhyaenid
Borhyaenidae
The borhyaenids, members of the Borhyaenidae family of metatherians , were a carnivorous group of otter/wolverine-shaped marsupials in the order Sparassodonta. They lived in the Miocene of South America . Like most metatherians, they had a pouch to carry their offspring around...

s and the saber-toothed Thylacosmilus
Thylacosmilus
Thylacosmilus was a genus of sabre-toothed metatherian predators that first appeared during the Miocene. Remains of the animal have been found in parts of South America, primarily Argentina...

. South American niches for mammalian carnivores were dominated by these marsupial and sparassodont
Sparassodonta
Sparassodonta is an extinct order of carnivorous metatherian mammals native to South America. They were once considered to be true marsupials, but are now thought to be a sister taxon to them. A number of these mammalian predators closely resemble placental predators that evolved separately on...

 metatherians. While placental predators were absent, the metatherians did have to contend with avian (terror bird
Phorusrhacidae
Phorusrhacids , colloquially known as "terror birds" as the larger species were apex predators during the Miocene, were a clade of large carnivorous flightless birds that were the dominant predators in South America during the Cenozoic, 62–2 million years ago. They were roughly 1–3 meters tall...

) and terrestrial crocodilian competition. South America and Antarctica remained connected until 35 mya, as shown by the unique fossils found there. North and South America remained disjointed until about three million years ago, when the Isthmus of Panama
Isthmus of Panama
The Isthmus of Panama, also historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country of Panama and the Panama Canal...

 formed. This led to the Great American Interchange
Great American Interchange
The Great American Interchange was an important paleozoogeographic event in which land and freshwater fauna migrated from North America via Central America to South America and vice versa, as the volcanic Isthmus of Panama rose up from the sea floor and bridged the formerly separated continents...

. Competition from placental mammals from the north drove sparassodonts to extinction, while didelphimorphs (opossums) invaded Central America, with the Virginia opossum
Virginia Opossum
The Virginia opossum , commonly known as the North American opossum or tlacuache in Mexico, is the only marsupial found in North America north of Mexico. A solitary and nocturnal animal about the size of a domestic cat, and thus the largest opossum, it is a successful opportunist...

 reaching as far north as Canada.

Marsupials reached Australia via Antarctica about 50 mya, shortly after Australia had split off. This suggests a single dispersion event of just one species, most likely a relative to South America's monito del monte
Monito del Monte
The Monito del Monte The Monito del Monte The Monito del Monte (Spanish for "little mountain monkey", Dromiciops gliroides, is a diminutive marsupial native only to southwestern South America (Chile and Argentina). It is the only extant species in the ancient order Microbiotheria, and the sole New...

 (a microbiothere
Microbiotheria
The Monito del Monte is the only extant member of its family and the only surviving member of an ancient order, the Microbiotheria. The oldest microbiothere currently recognised is Khasia cordillerensis, based on fossil teeth from Early Palaeocene deposits at Tiupampa, Bolivia...

, the only New World australidelphia
Australidelphia
Australidelphia is the superorder that contains roughly three-quarters of all marsupials, including all those native to Australasia and a single species from South America...

n). This progenitor may have rafted
Rafting event
Oceanic dispersal is a type of biological dispersal that occurs when organisms transfer from one land mass to another by way of a sea crossing on large clumps of floating vegetation. Such matted clumps of vegetation are often seen floating down major rivers in the tropics and washing out to sea,...

 across the widening, but still narrow, gap between Australia and Antarctica. In Australia, they radiated into the wide variety we see today, island hopping
Island hopping
Island hopping is a term that refers to the means of crossing an ocean by a series of shorter journeys between islands, as opposed to a single journey directly across the ocean to the destination.- Forms :...

 some way through the Indonesian archipelago. A 2010 analysis of retrotransposon insertion sites
Retrotransposon Marker
Retrotransposon markers are retrotransposons that are used as cladistic markers.The analysis of SINEs – Short INterspersed Elements – LINEs – Long INterspersed Elements – or truncated LTRs – Long Terminal Repeats – as molecular cladistic markers represents a particularly interesting complement to...

 in the nuclear DNA
Nuclear DNA
Nuclear DNA, nuclear deoxyribonucleic acid , is DNA contained within a nucleus of eukaryotic organisms. In mammals and vertebrates, nuclear DNA encodes more of the genome than the mitochondrial DNA and is composed of information inherited from two parents, one male, and one female, rather than...

 of a variety of marsupials has confirmed all living marsupials have South American ancestors. The branching sequence of marsupial orders indicated by the study puts Didelphimorphia in the most basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

 position, followed by Paucituberculata, then Microbiotheria, and ending with the radiation of Australian marsupials. This indicates that Australidelphia arose in South America, and reached Australia after Microbiotheria split off.

In Australia, terrestrial placental mammals disappeared early in the Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...

 (their most recent known fossils being 55 million year old teeth resembling those of condylarth
Condylarth
Condylarthra is an order of extinct placental mammals known primarily from the Paleocene and Eocene epochs. Condylarths are among the most characteristic Paleocene mammals and they illustrate the evolutionary level of the Paleocene mammal fauna....

s) for reasons that are not clear, allowing marsupials to dominate the Australian ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

. Extant native Australian terrestrial placental mammals (such as hopping mice
Hopping mouse
A hopping mouse is any of about ten different Australian native mice in the genus Notomys. They are rodents, not marsupials, and their ancestors are thought to have arrived from Asia about 5 million years ago....

) are relatively recent immigrants, arriving via island hopping from southeast Asia.

Early development

An early birth removes a developing marsupial from its parent's body much sooner than in placental mammals, and thus marsupials have not developed a complex placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

 to protect the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

 from its mother's immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

. Though early birth places the tiny newborn marsupial at a greater environmental risk, it significantly reduces the dangers associated with long pregnancies, as there is no need to carry a large fetus to full-term in bad seasons.

Because newborn marsupials must climb up to their mother's nipples, their front limbs are much more developed than the rest of the body at the time of birth. It is possible that this requirement has resulted in the limited range of locomotor adaptations in marsupials compared to placentals. Marsupials must develop a grasping forepaw during their early youth, making the transition from this limb into a hoof
Hoof
A hoof , plural hooves or hoofs , is the tip of a toe of an ungulate mammal, strengthened by a thick horny covering. The hoof consists of a hard or rubbery sole, and a hard wall formed by a thick nail rolled around the tip of the toe. The weight of the animal is normally borne by both the sole...

, wing
Wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...

, or flipper
Flipper (anatomy)
A flipper is a typically flat limb evolved for movement through water. Various creatures have evolved flippers, for example penguins , cetaceans A flipper is a typically flat limb evolved for movement through water. Various creatures have evolved flippers, for example penguins (also called...

, as some groups of placental mammals have done, far more difficult.

An infant marsupial is known as a joey. Marsupials have an extremely short gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....

 period (about 4–5 weeks), and the joey is 'born' essentially in a fetal
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 state. The blind, furless, miniature newborn, the size of a jelly bean
Jelly bean
Jelly beans are a small bean-shaped type of confectionery with a hard candy shell and a gummy interior which come in a wide variety of flavors. The confection is primarily made of sugar.-History:...

, crawls across its mother's fur to make its way into the pouch
Pouch (marsupial)
The pouch is a distinguishing feature of female marsupials ; the name marsupial is derived from the Latin marsupium, meaning "pouch". Marsupials give birth to a live but relatively undeveloped fetus called a joey. When the joey is born it crawls from inside the mother to the pouch...

, where it latches onto a teat for food. It will not re-emerge for several months, during which time it develops fully. After this period, the joey begins to spend increasing lengths of time out of the pouch, feeding and learning survival skills. However, it returns to the pouch to sleep, and if danger threatens it will seek refuge in its mother's pouch for safety.

Joeys stay in the pouch for up to a year in some species, or until the next joey is born. A marsupial joey is unable to regulate its own body temperature, and thus relies upon an external heat source. Until the joey is well-furred and old enough to leave the pouch, a pouch temperature between 30–32 °C (86–89.6 F) must be constantly maintained.

Reproductive system

Marsupials' reproductive systems differ markedly from those of placental mammals (Placentalia
Eutheria
Eutheria is a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials . They are distinguished from noneutherians by various features of the feet, ankles, jaws and teeth...

). Females have two lateral vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

s, which lead to separate uteri but both open externally through the same orifice. A third canal, the median vagina, is used for birth. This canal can be transitory or permanent. The males generally have a two-pronged penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...

, which corresponds to the females' two vaginas. The penis is used only for discharging semen
Semen
Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...

 into females, and there is instead a urogenital sac used to store waste before expulsion.

Pregnant females develop a kind of yolk sac in their wombs, which delivers nutrients to the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

. Marsupials give birth at a very early stage of development (about 4–5 weeks); after birth, newborn marsupials crawl up the bodies of their mothers and attach themselves to a nipple, which is located on the underside of the mother either inside a pouch called the marsupium or open to the environment. To crawl to the nipple and attach to it, the marsupial must have well developed forelimbs and facial structures. This is accomplished by accelerating forelimb and facial development in marsupials compared to placental mammals. As a result, there is decelerated development of such structures as the hindlimb and brain. There they remain for a number of weeks, attached to the nipple. The offspring are eventually able to leave the marsupium for short periods, returning to it for warmth, protection and nourishment.

Characteristics

Marsupials are characterized by giving birth to relatively undeveloped young. They lack a complex placenta to protect the embryo from its mother's immune system. They have a front pouch
Pouch (marsupial)
The pouch is a distinguishing feature of female marsupials ; the name marsupial is derived from the Latin marsupium, meaning "pouch". Marsupials give birth to a live but relatively undeveloped fetus called a joey. When the joey is born it crawls from inside the mother to the pouch...

 containing multiple nipples for protection and sustenance of the young.

Some common structural features can be found among marsupials. Ossified
Ossification
Ossification is the process of laying down new bone material by cells called osteoblasts. It is synonymous with bone tissue formation...

 patellae are absent. Marsupials (and also monotreme
Monotreme
Monotremes are mammals that lay eggs instead of giving birth to live young like marsupials and placental mammals...

s) also lack a gross communication (corpus callosum
Corpus callosum
The corpus callosum , also known as the colossal commissure, is a wide, flat bundle of neural fibers beneath the cortex in the eutherian brain at the longitudinal fissure. It connects the left and right cerebral hemispheres and facilitates interhemispheric communication...

) between the right and left brain hemisphere.

Taxonomy

Taxonomically
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

, there are two primary divisions of Marsupialia: American
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

 marsupials and the Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

n marsupials. The Order Microbiotheria
Microbiotheria
The Monito del Monte is the only extant member of its family and the only surviving member of an ancient order, the Microbiotheria. The oldest microbiothere currently recognised is Khasia cordillerensis, based on fossil teeth from Early Palaeocene deposits at Tiupampa, Bolivia...

 (which has only one species, the monito del monte) is found in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

, but is believed to be more closely related to the Australian marsupials. There are many small arboreal species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in each group. The term opossums is properly used to refer to the American species (though possum is a common diminutive), while similar Australian species are properly called possum
Possum
A possum is any of about 70 small to medium-sized arboreal marsupial species native to Australia, New Guinea, and Sulawesi .Possums are quadrupedal diprotodont marsupials with long tails...

s
.
    • Order †Sparassodonta
      Sparassodonta
      Sparassodonta is an extinct order of carnivorous metatherian mammals native to South America. They were once considered to be true marsupials, but are now thought to be a sister taxon to them. A number of these mammalian predators closely resemble placental predators that evolved separately on...

       (formerly viewed as marsupials, now as a sister group of metatheria
      Metatheria
      Metatheria is a grouping within the animal class Mammalia. First proposed by Thomas Henry Huxley in 1880, it is nearly synonymous with the earlier taxon Marsupialia though it is slightly wider since it also contains the nearest fossil relatives of marsupial mammals.The earliest known...

      ns)
  • Superorder Ameridelphia
    Ameridelphia
    Ameridelphia is traditionally a superorder that includes all marsupials living in the Americas except for the Monito del Monte...

    • Order Didelphimorphia
      Didelphimorphia
      Opossums make up the largest order of marsupials in the Western Hemisphere, including 103 or more species in 19 genera. They are also commonly called possums, though that term technically refers to Australian fauna of the suborder Phalangeriformes. The Virginia opossum was the first animal to be...

       (93 species)
      • Family Didelphidae: opossums
    • Order Paucituberculata (6 species)
      • Family Caenolestidae: shrew opossum
        Shrew opossum
        The order Paucituberculata contains the six surviving species of shrew opossum: small, shrew-like marsupials which are confined to the Andes mountains of South America. It is thought that the order diverged from the ancestral marsupial line very early. As recently as 20 million years ago, there...

        s
  • Superorder Australidelphia
    Australidelphia
    Australidelphia is the superorder that contains roughly three-quarters of all marsupials, including all those native to Australasia and a single species from South America...

    • Order Microbiotheria
      Microbiotheria
      The Monito del Monte is the only extant member of its family and the only surviving member of an ancient order, the Microbiotheria. The oldest microbiothere currently recognised is Khasia cordillerensis, based on fossil teeth from Early Palaeocene deposits at Tiupampa, Bolivia...

       (1 species)
      • Family Microbiotheriidae: monito del monte
        Monito del Monte
        The Monito del Monte The Monito del Monte The Monito del Monte (Spanish for "little mountain monkey", Dromiciops gliroides, is a diminutive marsupial native only to southwestern South America (Chile and Argentina). It is the only extant species in the ancient order Microbiotheria, and the sole New...

    • Order †Yalkaparidontia
    • Order Dasyuromorphia
      Dasyuromorphia
      The order Dasyuromorphia comprises most of the Australian carnivorous marsupials, including quolls, dunnarts, the numbat, the Tasmanian devil, and the recently extinct thylacine...

       (71 species)
      • Family †Thylacinidae
        Thylacinidae
        The animals in the Thylacinidae family were all carnivorous marsupials from the order Dasyuromorphia. The only recent member was the Thylacine , which became extinct in 1936...

        : thylacine
        Thylacine
        The thylacine or ,also ;binomial name: Thylacinus cynocephalus, Greek for "dog-headed pouched one") was the largest known carnivorous marsupial of modern times. It is commonly known as the Tasmanian tiger or the Tasmanian wolf...

      • Family Dasyuridae
        Dasyuridae
        Dasyuridae is a family of marsupials native to Australia and New Guinea, including 61 species divided into 15 genera. Many are small and mouse-like, giving them the misnomer marsupial mice, but the group also includes the cat-sized quolls, as well as the Tasmanian Devil...

        : antechinus
        Antechinus
        Antechinus is a genus of dasyurid marsupial that is indigenous to Australia and New Guinea. The majority of Antechinus species occur in Australia and only two species have been described in New Guinea...

        es, quoll
        Quoll
        The quoll, or native cat, is a carnivorous marsupial native to mainland Australia, New Guinea and Tasmania. It is primarily nocturnal and spends most of the day in its den. There are six species of quoll; four are found in Australia and two in New Guinea...

        s, dunnart
        Dunnart
        Dunnarts are furry narrow-footed marsupials the size of a mouse, members of the genus Sminthopsis. They are mainly insectivorous. A male dunnart's Y chromosome has only 4 genes, making it the smallest known mammalian Y chromosome....

        s, Tasmanian devil
        Tasmanian Devil
        The Tasmanian devil is a carnivorous marsupial of the family Dasyuridae, now found in the wild only on the Australian island state of Tasmania. The size of a small dog, it became the largest carnivorous marsupial in the world following the extinction of the thylacine in 1936...

        , and relatives
      • Family Myrmecobiidae: numbat
        Numbat
        The numbat , also known as the banded anteater, or walpurti, is a marsupial found in Western Australia. Its diet consists almost exclusively of termites. Once widespread across southern Australia, the range is now restricted to several small colonies and it is listed as an endangered species...

    • Order Peramelemorphia
      Peramelemorphia
      The order Peramelemorphia includes the bandicoots and bilbies: it equates approximately to the mainstream of marsupial omnivores...

       (24 species)
      • Family Thylacomyidae: bilbies
        Bilby
        Bilbies are desert-dwelling marsupial omnivores; they are members of the order Peramelemorphia. Before European colonisation of Australia, there were two species. One became extinct in the 1950s; the other survives but remains endangered....

      • Family †Chaeropodidae: pig-footed bandicoot
        Pig-footed Bandicoot
        The Pig-footed Bandicoot, Chaeropus ecaudatus, was a small marsupial of the arid and semi-arid plains of Australia. The distribution range of the species was later reduced to an inland desert region, where it was last recorded in the 1950s, and is now presumed to be extinct.-Classification:This...

      • Family Peramelidae
        Peramelidae
        Peramelidae is the family of marsupials that contains all of the extant bandicoots. One known extinct species of bandicoot, the Pig-footed Bandicoot, was so different than the other species that it was recently moved into its own family. There are four described fossil Peramelids...

        : bandicoot
        Bandicoot
        Bandicoots are a group of about 20 species of small to medium-sized, terrestrial marsupial omnivores in the order Peramelemorphia.- Etymology :...

        s and allies
    • Order Notoryctemorphia (2 species)
      • Family Notoryctidae: marsupial mole
        Marsupial mole
        Marsupial moles is a family of marsupials of the order Notoryctemorphia, consisting of only two extant species:* Notoryctes typhlops * Notoryctes caurinus ...

        s
    • Order Diprotodontia
      Diprotodontia
      Diprotodontia is a large order of about 120 marsupial mammals including the kangaroos, wallabies, possums, koala, wombats, and many others. Extinct diprotodonts include the rhinoceros-sized Diprotodon, and Thylacoleo, the so-called "marsupial lion"....

       (137 species)
      • Family Phascolarctidae
        Phascolarctidae
        Phascolarctidae is a family of marsupials of the order Diprotodontia, consisting of only one extant species, the Koala, six well known fossil species, with another 5 less well known fossil species, and 2 fossil species whose taxonomy is debatable but is put in this group...

        : koala
        Koala
        The koala is an arboreal herbivorous marsupial native to Australia, and the only extant representative of the family Phascolarctidae....

      • Family Vombatidae: wombat
        Wombat
        Wombats are Australian marsupials; they are short-legged, muscular quadrupeds, approximately in length with a short, stubby tail. They are adaptable in their habitat tolerances, and are found in forested, mountainous, and heathland areas of south-eastern Australia, including Tasmania, as well as...

        s
      • Family †Diprotodontidae
        Diprotodontidae
        Diprotodontidae is an extinct family of large, actively mobile marsupial, endemic to what would be Australia, during the Oligocene through Pleistocene periods from 28.4 mya—11,000 years ago, existing for approximately .-References:...

        : diprotodon
        Diprotodon
        Diprotodon, meaning "two forward teeth", sometimes known as the Giant Wombat or the Rhinoceros Wombat, was the largest known marsupial that ever lived...

      • Family Phalangeridae
        Phalangeridae
        Phalangeridae is a family of nocturnal marsupials native to Australia and New Guinea, including the cuscuses, brushtail possums, and their close relatives...

        : brushtail possum
        Brushtail possum
        The brushtail possums are the members of the genus, Trichosurus, a genus of marsupial in the Phalangeridae family.It contains the following species:*Northern Brushtail Possum, Trichosurus arnhemensis...

        s and cuscus
        Cuscus
        Cuscus is the common name generally given to the species within the four genera of Australasian possum:* Ailurops* Phalanger* Spilocuscus* Strigocuscus...

        es
      • Family Burramyidae: pygmy possum
        Pygmy possum
        The pygmy possums are a family of small possums that together form the marsupial family Burramyidae. There are five extant species of pygmy possum, grouped into two genera. Four of the species are endemic to Australia, with one species also co-occurring in Papua New Guinea and Indonesia.Pygmy...

        s
      • Family Tarsipedidae: honey possum
        Honey Possum
        The honey possum or tait, its Native Australian name or noolbenger is a tiny Australian marsupial weighing just seven to eleven grams for the male, and eight to sixteen grams for the female—about half the weight of a mouse. Their physical size ranges from a body length of between 6.5 –...

      • Family Petauridae
        Petauridae
        The family Petauridae includes 11 medium-sized possum species: four striped possums, the six species wrist-winged gliders in genus Petaurus, and Leadbeater's Possum which has only vestigal gliding membranes...

        : striped possum
        Striped Possum
        The Striped Possum is a member of the Petauridae family, one of the marsupial families. The species is black with three white stripes running head to tail, and its head has white stripes that form a 'Y' shape...

        , Leadbeater's possum
        Leadbeater's Possum
        Leadbeater's Possum is an endangered possum restricted to small pockets of remaining old growth mountain ash forests in the central highlands of Victoria north-east of Melbourne...

        , yellow-bellied glider
        Yellow-bellied Glider
        The Yellow-bellied Glider is an arboreal and nocturnal gliding possum that lives in a narrow range of native eucalypt forests down eastern Australia, reaching from northern Queensland to Victoria.-Habitat:...

        , sugar glider
        Sugar Glider
        The sugar glider is a small gliding possum originating from the marsupial family.The sugar glider is native to eastern and northern mainland Australia and is also native to New Guinea and the Bismarck Archipelago.- Habitat :Sugar gliders can be found all throughout the northern and eastern parts of...

        , mahogany glider
        Mahogany Glider
        The mahogany glider is an endangered gliding possum native to a small region of coastal Queensland.-Appearance:A nocturnal arboreal marsupial, the mahogany glider closely resembles the sugar glider, the squirrel glider and the yellow-bellied glider., but is noticeably larger than any of its...

        , squirrel glider
        Squirrel Glider
        The Squirrel Glider is a nocturnal gliding possum, one of the wrist-winged gliders of the genus Petaurus.-Habitat:...

      • Family Pseudocheiridae
        Pseudocheiridae
        Pseudocheiridae is a family of arboreal marsupials containing 17 extant species of ringtailed possums and close relatives. They are found in forested areas and shrublands throughout Australia and New Guinea.-Characteristics:...

        : ringtailed possums
        Common Ringtail Possum
        The common ringtail possum is an Australian marsupial. It lives in a variety of habitats and eats a variety of leaves of both native and introduced plants, as well as flowers and fruits. These dietary factors have, over time, aided burgeoning introduced populations in New Zealand...

         and relatives
      • Family Potoridae: potoroo
        Potoroo
        The Potoroo is a kangaroo/rat like animal about the size of a rabbit. All three extant species are threatened, especially The long-footed Potoroo and Gilbert's potoroo...

        s, rat kangaroos, bettong
        Bettong
        The bettongs are species of the genus Bettongia, sometimes referred to as rat-kangaroos. Five species are recognised:* Eastern Bettong, Bettongia gaimardi* Boodie, Bettongia lesueur...

        s
      • Family Acrobatidae
        Acrobatidae
        Acrobatidae is a small family of gliding marsupials containing two genera, each with a single species, the Feathertail Glider from Australia and Feather-tailed Possum from New Guinea....

        : feathertail glider
        Feathertail Glider
        The Feathertail Glider , also known as the Pygmy Gliding Possum, Pygmy Glider, Pygmy Phalanger, Flying Phalanger and Flying Mouse, is the world's smallest gliding possum and is named for its long feather-shaped tail. Although only the size of a very small mouse , it can leap and glide up to 25 metres...

         and feather-tailed possum
        Feather-tailed Possum
        The Feather-tailed Possum is a species of marsupial in the Acrobatidae family. It is found in West Papua, Indonesia and Papua New Guinea.It is the only species in the genus Distoechurus....

      • Family Hypsiprymnodontidae
        Hypsiprymnodontidae
        The Hypsiprymnodontidae are a family of macropods, one of two families containing animals commonly referred to as rat-kangaroos. There is a single known extant genus and species in this family, the Musky Rat-kangaroo, Hypsiprymnodon moschatus, which occurs in northern Australia and New Guinea....

        : musky rat-kangaroo
        Musky Rat-kangaroo
        The Musky Rat-kangaroo is a marsupial species found in the rainforests of northeast Australia. Although some scientists place this species as a subfamily of the family Potoroidae, the most recent classification places it in the family Hypsiprymnodontidae with prehistoric rat-kangaroos.It is the...

      • Family Macropodidae: kangaroo
        Kangaroo
        A kangaroo is a marsupial from the family Macropodidae . In common use the term is used to describe the largest species from this family, especially those of the genus Macropus, Red Kangaroo, Antilopine Kangaroo, Eastern Grey Kangaroo and Western Grey Kangaroo. Kangaroos are endemic to the country...

        s, wallabies
        Wallaby
        A wallaby is any of about thirty species of macropod . It is an informal designation generally used for any macropod that is smaller than a kangaroo or wallaroo that has not been given some other name.-Overview:...

        , and relatives
      • Family †Thylacoleonidae
        Thylacoleonidae
        Thylacoleonidae is a family of extinct meat-eating marsupials from Australia, referred to as marsupial lions. The best known is Thylacoleo carnifex, also called the Marsupial Lion...

        : marsupial lion
        Marsupial lion
        Thylacoleo is an extinct genus of carnivorous marsupials that lived in Australia from the late Pliocene to the late Pleistocene...

        s


† indicates extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK