A report on Metatheria

Mammalian clade that includes all mammals more closely related to marsupials than to placentals.

- Metatheria

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Marsupial

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Marsupials are any members of the mammalian infraclass Marsupialia.

Marsupials are any members of the mammalian infraclass Marsupialia.

Koala
(Phascolarctos cinereus)
Female eastern grey kangaroo with a joey in her pouch
Reproductive tract of a male macropod
Female reproductive anatomy of several marsupial species
Child holding rescued agile wallaby joey. Cooktown. 2008
Isolated petrosals of Djarthia murgonensis, Australia's oldest marsupial fossils
Dentition of the herbivorous eastern grey kangaroo, as illustrated in Knight's Sketches in Natural History
Phylogenetic tree of marsupials derived from retroposon data

Marsupials represent the clade originating from the last common ancestor of extant metatherians, the group containing all mammals more closely related to marsupials than to placentals.

Monotreme

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Monotremes are prototherian mammals of the order Monotremata.

Monotremes are prototherian mammals of the order Monotremata.

Platypus
Long-beaked echidna
Diagram of a monotreme egg. (1) Shell; (2) Yolk; (3) Yolk Sac; (4) Allantois; (5) Embryo; (6) Amniotic Fluid; (7) Amniotic Membrane; and (8) Membrane
Monotreme female reproductive organs
Male platypus reproductive system. 1. Testes, 2. Epididymis, 3. Bladder, 4. Rectum, 5. Ureter, 6. Vas Deferens, 7. Genito-urinary sinus, 8. Penis enclosed in a fibrous sheath, 9. Cloaca, 10. Opening in the ventral wall of the cloaca for the penis.
A model of the extinct platypod Steropodon at the Australian Museum.
A 100 million-year-old Steropodon jaw on display at the American Museum of Natural History, New York City, USA

They are one of the three groups of living mammals, along with placentals (Eutheria) and marsupials (Metatheria).

The original synapsid skull structure contains one temporal opening behind the orbitals, in a fairly low position on the skull (lower right in this image). This opening might have assisted in containing the jaw muscles of these organisms which could have increased their biting strength.

Mammal

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Mammals are a group of vertebrate animals constituting the class Mammalia, characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or hair, and three middle ear bones.

Mammals are a group of vertebrate animals constituting the class Mammalia, characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or hair, and three middle ear bones.

The original synapsid skull structure contains one temporal opening behind the orbitals, in a fairly low position on the skull (lower right in this image). This opening might have assisted in containing the jaw muscles of these organisms which could have increased their biting strength.
Restoration of Juramaia sinensis, the oldest known Eutherian (160 M.Y.A.)
Fossil of Thrinaxodon at the National Museum of Natural History
Raccoon lungs being inflated manually
Mammal skin: 1 — hair, 2 — epidermis, 3 — sebaceous gland, 4 — Arrector pili muscle, 5 — dermis, 6 — hair follicle, 7 — sweat gland, 8 (not labeled, the bottom layer) — hypodermis, showing round adipocytes
Bovine kidney
A diagram of ultrasonic signals emitted by a bat, and the echo from a nearby object
Porcupines use their spines for defense.
A leopard's disruptively colored coat provides camouflage for this ambush predator.
Goat kids stay with their mother until they are weaned.
Matschie's tree-kangaroo with young in pouch
Running gait. Photographs by Eadweard Muybridge, 1887.
Gibbons are very good brachiators because their elongated limbs enable them to easily swing and grasp on to branches.
Vervet monkeys use at least four distinct alarm calls for different predators.
A bonobo fishing for termites with a stick
Female elephants live in stable groups, along with their offspring.
Red kangaroos "boxing" for dominance
Upper Paleolithic cave painting of a variety of large mammals, Lascaux, c. 17,300 years old
Cattle have been kept for milk for thousands of years.
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Biodiversity of large mammal species per continent before and after humans arrived there
Sexual dimorphism in aurochs, the extinct wild ancestor of cattle.

The earliest known metatherian is Sinodelphys, found in 125 million-year-old Early Cretaceous shale in China's northeastern Liaoning Province.

Opossum

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Opossums are members of the marsupial order Didelphimorphia endemic to the Americas.

Opossums are members of the marsupial order Didelphimorphia endemic to the Americas.

Skeleton of the gray short-tailed opossum (Monodelphis domestica)
An opossum on top of a fence
Virginia opossum feigning death, or "playing possum"
Juvenile Virginia opossum hissing defensively
D. virginiana range, including introductions in the west. Currently these areas are expanding northwards (e.g., into Wisconsin and Minnesota).
A 'possum joke sign

Many extinct metatherians once considered early opossums, such as Alphadon, Peradectes, Herpetotherium, and Pucadelphys, have since been recognized to have been previously grouped with opossums on the basis of plesiomorphies and are now considered to represent older branches of Metatheria only distantly related to modern opossums.

Sparassodonta

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The skeleton of Lycopsis longirostrus, from the late middle Miocene of Colombia.
Skull of Borhyaena (Borhyaenidae)
Skeletal reconstruction of Thylacosmilus, a large specialised sabre-toothed sparassodont

Sparassodonta (from Greek σπαράσσειν [sparassein], to tear, rend; and ὀδούς, gen. ὀδόντος [odous, odontos], tooth) is an extinct order of carnivorous metatherian mammals native to South America, related to modern marsupials.

Subdivisions of the Miocene

Miocene

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First geological epoch of the Neogene Period and extends from about .

First geological epoch of the Neogene Period and extends from about .

Subdivisions of the Miocene
Japan during the Early Miocene
The Mediterranean during the Late Miocene
The dragon blood tree is considered a remnant of the Mio-Pliocene Laurasian subtropical forests that are now almost extinct in North Africa.
Cameloid footprint (Lamaichnum alfi Sarjeant and Reynolds, 1999; convex hyporelief) from the Barstow Formation (Miocene) of Rainbow Basin, California.
Fossils from the Calvert Formation, Zone 10, Calvert Co., MD (Miocene)
A Miocene crab (Tumidocarcinus giganteus) from the collection of the Children's Museum of Indianapolis

The youngest known representatives of metatherians (marsupial relatives) in the Northern Hemisphere landmasses (Asia, North America and Europe) and Africa are known from the Miocene, including the North American herpetotheriid Herpetotherium, the European herpetotheriid Amphiperatherium, the peradectids Siamoperadectes and Sinoperadectes from Asia, and the possible herpetotheriid Morotodon from the late Early Miocene of Uganda.

Dasyuromorphia

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Order comprising most of the Australian carnivorous marsupials, including quolls, dunnarts, the numbat, the Tasmanian devil, and the thylacine.

Order comprising most of the Australian carnivorous marsupials, including quolls, dunnarts, the numbat, the Tasmanian devil, and the thylacine.

Numerous South American species of marsupials (orders Didelphimorphia, Paucituberculata, and Microbiotheria) are also carnivorous, as were some extinct members of the order Diprotodontia, including extinct kangaroos (such as Ekaltadeta and Propleopus) and thylacoleonids, and some members of the partially extinct clade Metatheria and all members of the extinct superorder Sparassodonta.

Herpetotheriidae

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Herpetotheriidae is an extinct family of metatherians, closely related to marsupials.

Early Cretaceous

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Earlier or lower of the two major divisions of the Cretaceous.

Earlier or lower of the two major divisions of the Cretaceous.

Sinodelphys was more closely related to metatherians (marsupials) than eutherians (placentals) and had feet adapted from climbing trees.

Herpetotherium

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Herpetotherium fugax
Restoration

Herpetotherium is an extinct genus of metatherian mammal, belonging to the possibly paraphyletic family Herpetotheriidae.