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Didelphimorphia

Scientific classification
Kingdom:Animalia
Class:Mammalia
Subclass:Marsupialia
Magnorder:Ameridelphia
Order:Didelphimorphia
Family:Didelphidae
Genera
Several; see text

The order Didelphimorphia contains the common opossums of the western hemisphere. Opossums probably diverged from the basic South American Ameridelphian stock in the latest Cretaceous or early Paleocene. A sister group is the Paucituberculata, or shrew opossums.

Didelphimorphs are small to medium-sized marsupials. They tend to be semi-arboreal omnivores, although there are many exceptions. Most members of this taxon have long snouts, a narrow braincase, and a prominent sagittal crest (a bone crest running longitudinally along the center of the skull). The dental formula (one side of one jaw) includes 5 incisors (4 on the lower jaw), 1 canine, 3 premolars and 4 molars. By mammal standards, this is a very full jaw. The incisors are very small, the canines large. The molars are tricuspid .

Didelphimorphs have a plantigrad e stance (feet flat on the ground). Most unusually, the hind feet have an opposable digit with a nail—not a claw. Nails are otherwise rare in the animal world and are common only among primates. Also like primates, opossums may have prehensile tails. The stomach is simple, with a small cecumIn anatomy of the digestive system, the cecum or caecum is a pouch connected to the large intestine between the ileum and the colon. It is separated from the ileum by the ileocecal valve (ICV) or Bauhin's valve, and is considered to be the beginning of th. Opossum reproductive systems are extremely basic, with a reduced marsupium . This means that the young are born at a very early stage. Females are usually somewhat larger than males.

Didelphimorphs are opportunistic omnivores with a very broad range of diet. Their unspecialized biology, flexible diet and reproductive strategy make them successful colonizers and survivors in unsettled times. Perhaps this is why their range has been expanding rapidly into North AmericaNorth America is the third largest continent in area and the fourth ranked in population. It is bounded on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the south by the Caribbean Sea, and on the west by the North Pacific Ocea.

Classification

Within the familyIn biology, family is one of the levels of taxonomic classification of organisms. It lies between the less-specific order and the more-specific genus; ie, an order will contain one or more families, and a family will contain one or more genera. Humans, fo of the Didelphidae, the following species exist:

Mammals
Monotremata

Placentalia:

Xenarthra | Dermoptera | Desmostylia | Scandentia | Primates | Rodentia | Lagomorpha | Insectivora | Chiroptera | Pholidota | Carnivora | Perissodactyla | Artiodactyla | Cetacea | Afrosoricida | Macroscelidea | Tubulidentata | Hyracoidea | Proboscidea | Sirenia

Marsupialia: Didelphimorphia |

Paucituberculata | Microbiotheria | Dasyuromorphia | Peramelemorphia | Notoryctemorphia | Diprotodontia


Mammals

Opossums




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