This family includes the most primitive marsupials. All of its living representatives inhabit America. Fossil forms are known from the tertiary deposits of Europe.
American possums have an archaic dental formula: a complete series of incisors (5 on each side of the upper jaw), well-developed fangs (larger than the incisors), and sharply tubercular molars. In total, representatives of this family have 50 teeth. The primitive structure of the limbs is characteristic: they are five-fingered, all fingers are equally well developed. Usually the hind legs are more developed than the forepaws. The tail is in most cases long, grasping, bare at the end. The bag is often underdeveloped, and if developed, it opens back, which is also an archaic feature of the structure. All members of the family are predators or insectivores. In general, they play the same role in Central and South America as representatives of the insectivore detachment on other continents, which are scarce in tropical America.
The taxonomy of the family needs clarification and refinement. Currently, 11 genera and 75 species are attributed to the family. One of the representatives of the genus of common possums (Didelphis) - the North American possum is found in the southern half of North America. The rest inhabit Central and South America.
Virgin opossum (Didelphis virginiana) is widespread from southern Canada south to northern Peru, eastern Bolivia and Paraguay. It inhabits the eastern half of the USA, as well as the southern part of the Pacific coast of this country, where it was brought at the beginning of the 20th century.
Opossum is the size of a domestic cat, with short legs, a sharp light-colored face and bare ears with pinkish tips. The tail is almost naked, long, grasping type. The general coloration is usually gray, occasionally black animals come across. Females have developed a back-opening bag. Body length 36–53 cm, tail 25–33 cm, weight 1.6–5.7 kg.
Opossums inhabit the most diverse areas - both low-lying and elevated, mainly near water bodies. Active mainly at night. Compared to other mammals, they seem slow and stupid. In danger, they can pretend to be dead. Opossums climb beautifully with the help of the far set apart first toes and a muscular grasping tail.
By the autumn, possums gobble up a lot and in the winter they often remain inactive in their dens for several days. Over the past decades, the range of the possum has expanded somewhat to the north, but the cold limits this progress.
Females begin to breed at the age of one year. Hollows, hollows of soil under buildings, in garbage, etc. serve as a refuge. In the mouth and on a crocheted tail, the female brings the dry remains of plants to build a nest. Opossums have 1 brood in the north, and 2 broods per year in the rest of the range. The brood consists initially of 8-18 cubs. After leaving the bag, usually no more than 7 cubs remain. The mass of all newborns is 2 g, and 20 of these newborns fit freely in a teaspoon. With the help of well-developed claws on the front legs, they climb into the mother’s bag and attach to the nipples. After 2 months, their hair appears and their eyes open, and after another 5-10 days they begin to move independently and eat solid food. The young ones scramble along the back and sides of the mother, clinging to her coat, often holding the tail for her tail, raised above the back with the end forward. One brood is separated from another by a period of about 3.5 months. Life expectancy in nature for most possums is less than 2 years. In captivity, they can live for more than 7 years.
Opossums are almost omnivorous. They eat carrion, invertebrates, mice, reptiles, amphibians, mushrooms, many cultivated plants, especially corn and cereals.
Durable sandpaper and stiff opossum fur are used to make outerwear and finishes. Meat is edible. Opossums do some harm to gardens, fields, and houses, but this harm is often exaggerated.
Two other representatives of the genus of common possums: the southern possum (D. albiventris) and the common possum (D. marsupialis) - the inhabitants of the tropics and subtropics of South and partly Central America.
The vast majority of the rest of the American marsupials are tropical inhabitants. Representatives of 2 genera - four-eyed possums (Philander) and water possums (Chironectes) are more highly organized and have a well-developed bag.
The four-eyed opossum (Philander opossum) inhabits Central and South America, where it is found mainly in the highlands of the west of the mainland, south to Paraguay and Northeast Argentina, as well as in Guiana and Eastern Brazil. Inhabits forests near ponds. This is a moving dark gray animal, smaller than the North American possum. Over each eye he has a white spot, hence the name of the animal. The second representative of this genus (Ph. Mcilhennyi) is known only from Peru.
Water possum (Chironectes minimus) is the only representative of the genus. It inhabits Central America to the north to the Yucatan Peninsula and South America to Paraguay and Northeast Argentina. The length of the body is 27–32 cm, the tail is 35–40 cm. The coat is marbled black and gray, relatively short and thick. On the hind legs of the membrane. The bag is well-closed, "waterproof". This is the only representative of marsupials, well adapted to the aquatic lifestyle. Secretive, extremely rare animal living near small rivers and lakes. It feeds on small fish and other aquatic animals.
The remaining 8 genera of American marsupials combine smaller and low-organized ropes with a rudimentary bag.
The vast genus of mouse-shaped possums (Marmosa) has 46 species, almost all of them have very limited ranges. At least a third of the available species are mountain animals, distributed at considerable heights (2500 m and higher). The largest body length of the mouse-shaped possums is 21 cm, and the tail is 6–28 cm.
The genus of fluffy possums (Caluromys) has 3 species, common in Central and South America. These are animals with long and fluffy hair and a particularly long tail, naked at the end. Body length 18–29 cm, tail 27–49 cm. Fluffy possums lead a strictly nocturnal lifestyle. These are more “woody" animals than other members of the American possum family.
The genus of short-tailed possums (Monodelphis) includes 15 species. These are small (about 10 cm long) animals with a relatively short tail and an elongated muzzle, resembling our shrews. The range of the genus extends little beyond Brazil and some neighboring countries (Venezuela, Peru, Bolivia).
The genus of long-tailed possums (Metachirus) is represented by one species (M. nudicaudatus). This is a rather large animal (body length 26–27 cm, tail 33 cm), widespread in South and Central America, north to Nicaragua.
The remaining 4 genera of the family (Caluromysiops, Glironia, Lutreolina, Lestodelphis) each have one species. Their ranges are small and located on the periphery of the South American tropics, only the last - Patagonian possum (Lestodelphis halli) is found to the south - in the pampa of South Patagonia.
Opossumovye (Didelphidae) - a family of mammals of the marsupial marsupial. It includes the oldest and least specialized marsupials, which appeared at the end of the Cretaceous period and since then have hardly changed. All living representatives of the possum family inhabit the New World, although fossil forms are known from the tertiary deposits of Europe. Most marsupials in South America became extinct after the emergence of a natural bridge between South and North America, through which new species began to penetrate from north to south. Only possums could endure competition and even spread north.
The closest relatives of American possums are rat-shaped possums. / (Wikipedia)
Family: D> Marsupials of small sizes. The body length of opossums is 7–50 cm. The length of the tail is 4–55 cm. The muzzle is elongated and pointed. The ears of the possums are small or medium in size, un hairy. The tail is in most cases long and grasping, completely or partially naked, sometimes thickened at the base by deposits of fat. The limbs are shortened, five-fingered, the hind legs are slightly longer than the front ones. The thumb of the hind limb in large possums is opposed to other fingers and lacks a claw. Fingers do not grow together.
The hairline of possums in most cases is short, dense, the color varies from gray and yellowish brown to black. On the head there may be stripes (thick-haired, fluffy-tailed and ordinary opossums), dark peri-ocular rings (Chiloe possums and mouse-shaped possums) or under-eye light marks (Patagonian and four-eyed opossums). There may also be streaks on the back (water possums).
The bag of some representatives of the family of American possums is well developed and opens forward (ordinary and four-eyed possums) or back (water possums), while in others (long-tail possums) it is incomplete (in the form of two lateral skin folds) or completely absent (mouse-shaped and naked-tail possums). From 5 to 27 nipples are arranged in several rows or in the form of a ring.
In the skull, the facial section is elongated and pointed, the cerebral is small. The bones are semicircular. Zygomatic arch large .. Teeth have roots. Fangs are well developed. The incisors are small. Anterior molars of the tritubercular type. The vertebrae of the cervical 7, thoracic 13, lumbar 6, sacral 2, caudal 19–35.
The diploid number of chromosomes is 22 in common and thick-tailed possums and 14 in bushy and mouse-like possums. Inhabitants of forests of various types, steppes and semi-deserts, are found on the plains and in the mountains up to 4000 m above sea level. Most members of the family lead a terrestrial or arboreal lifestyle, and a water possum is a semi-aquatic.
The activity of possums is mainly evening and night. Most are omnivorous with a predominance of carnivores or carnivores. The mouse-like, four-eyed and water possums are monoestral, and ordinary opossums are polyester (females bring 2-3 litters per year) animals. The duration of pregnancy is 12-13 days. In the litter of cubs 4-11 (up to 25). The lactation period lasts up to 70-100 days. After leaving the bag, the cubs often move with their mother, holding on to the fur on her back. Maturity occurs at 6-8 months of age. Life expectancy from 5 to 8 years.
Distributed in the territory from southeastern Canada to the south through the eastern states of the USA and Mexico to about 52 ° S. w. in argentina. They are also found in the Lesser Antilles. The common possum is acclimatized in some western regions of the USA.
There are 12 genera in the family of American possums (84 species).