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MARSPALIES(Marsupialia), a large group of mammals, differing from placental, or higher animals, in features of anatomy and reproduction. Classification schemes vary, but many zoologists consider marsupials as a superorder, divided into a special subclass Metatheria (lower animals). The name of the group comes from the Greek. marsupios – bag, or small bag. Marsupials are common in Australia and New Guinea, as well as in North and South America, from southeastern Canada to Argentina. Wallabies were introduced into New Zealand, Great Britain, Germany, on Hawaiian Islands, and opossums - to the west of North America, where they settled from southwestern British Columbia to northern California.
The taxonomy of the group varies, but its modern members are generally divided into 16 families, 71 genera and 258 species, the majority of which (165) are found in Australia and New Guinea. The smallest marsupials are the honey badger ( Tarsipes rostratus) and marsupial mouse ( Planigale subtilissima). The body length of the first reaches 85 mm plus a 100 mm tail with a mass of 7 g in males and 10 g in females. The total body length of a marsupial mouse is up to 100 mm, with approximately half of it being the tail, and its weight is 10 g. The largest marsupial is the large gray kangaroo ( Macropus giganteus) height 1.5 m and weight 80 kg.
Bag.
Marsupials give birth to very small cubs - their weight does not reach 800 mg. The duration of feeding newborns always exceeds the pregnancy period, which ranges from 12 to 37 days. During the first half of the nursing period, each young is permanently attached to one of the teats. Its end, once in the baby’s round mouth, thickens inside, providing a strong connection.
In most species, the nipples are located inside a pouch formed by folds of skin on the mother's abdomen. The pouch opens forward or backward depending on the species and can close tightly due to the contraction of muscle fibers. Some small species there is no bag, but newborns are also constantly attached to the nipples, the muscles of which, contracting, pull the cubs close to the mother’s stomach.
The structure of the reproductive organs.
Modern mammals are divided into three groups, usually considered separate subclasses: monotremes (platypus and other oviparous animals), marsupials and placentals (dogs, monkeys, horses, etc.). This terminology is not entirely appropriate, since the placenta is temporary internal organ, which connects the mother with the developing embryo before its birth, is also formed in marsupials, although in most cases it has a less complex structure.
One of the anatomical features that distinguishes these three groups of mammals concerns the location of their ureters and genital tracts. In monotremes, like reptiles and birds, the ureters and genital ducts empty into top part rectum, which forms a common excretory chamber called the cloaca. Through a “single passage”, urine, sexual products, and feces are excreted from the body.
Marsupials and placentals have two excretory chambers - the upper (rectum) for feces and the lower (urogenital sinus) for urine and reproductive products, and the ureters empty into a special bladder.
Moving during evolution to a lower position, the ureters either pass between the two reproductive ducts or bend around them from the outside. In marsupials the first variant is observed, in placentals the second. This seemingly small feature clearly separates the two groups and leads to profound differences in the anatomy of the reproductive organs and its methods.
In female marsupials, the urogenital opening leads to a paired reproductive organ, consisting of two so-called. lateral vaginas and two uteruses. These vaginas are separated by ureters and cannot merge, like in placental ones, but are connected in front of the uterus, forming a special chamber - the so-called. middle vagina.
The lateral vaginas serve only to carry semen to the uterus and do not participate in the birth of young. During childbirth, the fetus passes from the uterus directly into the median vagina and then, through the birth canal specially formed in the thickness of the connective tissue, into the urogenital sinus and out. In most species this canal closes after birth, but in some kangaroos and honey gliders it remains open.
In males of most marsupial species, the penis is forked, probably to direct semen into both lateral vaginas.
Evolutionary history.
In addition to the characteristics of reproduction, there are other differences between marsupials and placentals. The former do not have a corpus callosum, i.e. a layer of nerve fibers connecting the right and left hemispheres of the brain, and producing heat (thermogenic) brown fat in the young, but there is a special shell around the egg. The number of chromosomes in marsupials ranges from 10 to 32, while in placentals it usually exceeds 40. The two groups also differ in their skeletal and dental structure, which helps to identify their fossil remains.
The presence of these features, supported by persistent biochemical differences (amino acid sequences in myoglobin and hemoglobin), suggests that marsupials and placentals are representatives of two long-separated evolutionary branches, the common ancestors of which lived in the Cretaceous period ca. 120 million years ago. The oldest known marsupials date back to the Upper Cretaceous of North America. Their remains belonging to the same era were also found in South America, which was connected with the Northern Isthmus throughout most of the Cretaceous period.
At the beginning of the Tertiary period (about 60 million years ago), marsupials settled from North America to Europe, North Africa and Central Asia, but became extinct on these continents about 20 million years ago. During this time, they achieved great diversity in South America, and when it reconnected with North America in the Pliocene (ca. 12 million years ago), many species of possums penetrated north from there. From one of them came the Virginia opossum ( Didelphis virginiana), which spread across eastern North America relatively recently - ca. 4000 years ago.
Marsupials probably came to Australia from South America through Antarctica, when these three continents were still connected, i.e. more than 50 million years ago. Their first finds in Australia date back to the Oligocene (about 25 million years ago), but they are already so diverse that we can talk about a powerful adaptive radiation that occurred after the separation of Australia from Antarctica. Nothing is known about the early history of Australian marsupials, but by the Miocene (15 million years ago), representatives of all modern, as well as extinct, families appeared. The latter include several large herbivores the size of rhinoceros ( Diprotodon And Zygomataurus), giant kangaroos ( Procoptodon And Sthenurus) and large predators, such as a lion-like Thylacoleo and wolf-like Thylacinus.
Currently, marsupials of Australia and New Guinea occupy the same ecological niches as placentals on other continents. Marsupial devil ( Sarcophilius) similar to wolverine; marsupial mice, rats and martens are similar to mongooses, weasels and shrews; wombat - woodchuck; small wallabies - for rabbits; and large kangaroos correspond to antelopes.
There are two subclasses of mammals - primal beasts and real beasts. The first group includes the order Monotremes. They differ from the latter in that they lay eggs, but the young that hatch from them are fed milk. Real animals are divided into two superorders - marsupials and placental mammals.
The former differ from the latter in that during pregnancy the female does not form a placenta - a temporary organ that provides a connection between the maternal and daughter organisms. But such animals have a pouch, which is intended for carrying a baby that is born incapable of independent life. This superorder includes only one order - Marsupials. And all other orders belong to the placentals, such as artiodactyls, pinnipeds, carnivores, primates, chiropterans, etc.
Classification
Marsupial mammals occupy an ambiguous position. According to some systems, this group of organisms represents an order, and according to others, an infraclass. Let's take the koala as an example. According to one option, its place in the classification looks like this:
- Domain - Eukaryotes.
- Kingdom - Animals.
- Type - Chordata.
- Subphylum - Vertebrates.
- Class - Mammals.
- Order - Marsupials.
- Family - Wombats.
Another option is this:
- Domain - Eukaryotes.
- Kingdom - Animals.
- Type - Chordata.
- Subphylum - Vertebrates.
- Class - Mammals.
- Infraclass - Marsupials.
- Order - Two-incisor marsupials.
- Suborder - Wombatidae.
- Family - Koalas.
Characteristics of marsupial mammals
Most species of this order are endemic, that is, they live only in a specific area. Most often this is Australia. Almost all marsupial mammals on the planet live on this continent. Most marsupials are listed in the Red Book.
Representatives of this species also inhabit New Guinea and are found in South and North America. Marsupial mammals are divided into nine families: Opossumidae, Bandicootidae, Carnivorous marsupials, Caenolestidae, Possumidae, Kangarooidae, Wombatidae. The oldest and most primitive of the families of this order are the Opossumidae, from which all other animals in this group originated. Let's take a closer look at each family and its representatives.
Marsupials outside Australia
The oldest family is Possumidae. Animals belonging to this group are one of the few marsupials that live outside of Australia.
They are common in America. This family includes marsupial mammals such as the smoky, oriental, brownie, velvet, and American possums. These are small animals, about 10 cm long, with a long tail and thick hair. They are predominantly nocturnal, feeding on insects and a variety of fruits. These animals are good at pretending to be dead in case of danger. Also outside of Australia, some species of kangaroos live in the territory, for example, wallabies.
Representatives of the order Marsupials living in Australia
These include most of the animals in this group. The most famous of them are mammals of the Kangaroo family. It includes such representatives as the large red kangaroo, bear kangaroo, long-eared kangaroo, western gray kangaroo, etc. These are large animals with a large tail, which serves as additional support for them. These mammals have underdeveloped front legs, but strong hind legs, which allows them to move by jumping long distances. The main diet of kangaroos consists of plants. The cubs of these animals are born measuring only three centimeters in length, and the female's gestation period is only about 30 days (up to 40, depending on the species). In addition, kangaroo rats belong to this family. Wombats are no less common in Australia. These are small animals whose muzzle is somewhat reminiscent of a bear, but their teeth are almost the same as those of rodents.
Wombats feed on the roots of various plants, all kinds of fruits and seeds. Their front paws have large claws, which allows them to dig more efficiently, because wombats are one of the animals that spend most of their lives in burrows underground. Marsupial moles are characterized by similar behavior - they are small animals that eat beetle larvae and seeds. They also differ in that they do not have a constant body temperature.
Marsupials listed in the Red Book
The most famous of these are koalas. They are on the verge of extinction, since the only product they feed on is eucalyptus leaves, and not all of them - out of 800 species of this plant, only 100 are eaten by koalas. Also included in the Red Book are the ring-tailed kangaroo, the northern long-haired wombat, the marsupial marten and others .
The largest and smallest animals of the order Marsupials
The largest mammal in this group is the large gray kangaroo, and the smallest is the honey possum, which feeds on plant pollen. The largest marsupial animal lives in South and Western Australia. Its weight can reach fifty kilograms, and its height is a little more than a meter.
The smallest marsupial mammal, Acrobates pygmaeus, lives only in Australia. Its weight rarely exceeds fifteen grams. This animal has a long tongue; it is needed to make it more convenient to get pollen and nectar from plants. Also, one of the smallest marsupials is the marsupial mouse, which also weighs about ten grams.
Order marsupials
In the class of mammals, the order of marsupials is more likely to attract our attention than others. We include under the name marsupials a significant number of diverse families of mammals, which, with the exception of the pouch, method of reproduction and genital organs, have very little in common with each other. They could rather be considered orders of a special subclass of mammals*.
* Within the class of mammals, marsupials and placentals constitute the subclass of animals (Theria), opposed to the subclass of primal animals (Prototheria).
When studying the animals related here, the thought arises that we are dealing with a group that especially flourished at a time when huge, clumsy amphibians, flying lizards and sea monsters like the ichthyosaur still lived on the earth. Very strong arguments suggest that marsupials are only slightly modified descendants of mammals of past geological periods. A more detailed study of marsupials and comparison with other mammals reveals that their appearance is very diverse and they often resemble representatives of other orders; but it is no less striking that their organization is more imperfect in comparison with those animals to which they resemble. If you do not pay attention to the pouch, then the marsupial wolf in appearance undoubtedly resembles a dog, the marsupial marten - with a civet, the marsupial mouse - with a shrew, the wombat - with a rodent, just as the marsupial squirrel is similar to a flying squirrel, and The kangaroo appears to have the head of a ruminant. However, the dental system and internal structure These marsupials show fundamental differences from the representatives of higher orders compared with them, and this does not allow them to be combined.
If we compare a marsupial animal with a carnivore or rodent, then even to the most undiscerning eye it becomes clear that it is in all respects less developed and less perfect than a similar predator or rodent. This backwardness of the marsupial is manifested either in the shape of the entire body, or in the structure of individual organs, or in the dental system. Our eye, accustomed to other forms of animals, always lacks something when examining a marsupial. Their dental system, compared to the dental systems of corresponding predators and rodents, turns out to be more imperfect and meager. The jaws of a predatory marsupial are equipped with a sufficient number of teeth, and their order is the same as that of predators. But they are less developed, or positioned incorrectly, or are much blunter, sometimes worse in color, less white and clean than the teeth of a real predator of later times. Thus, we can quite thoroughly accept that we are dealing with imperfect, not yet sufficiently developed beings*.
* Marsupials evolved in a relatively limited area of the three southern continents. In “greenhouse” conditions, marsupials did not need to constantly complicate their behavioral reactions and skills. The brain of marsupials has undergone virtually no changes, remaining small and simply structured. This is the reason for the “primitiveness” and “stupidity” of modern marsupials emphasized by Brehm. When the "real beasts" invaded the southern continents during the Late Cenozoic faunal exchange. Marsupials did not hold their position and now exist as relics only where placentals occupying the corresponding niche have not penetrated.
In general, very little can be said about the body structure of marsupials. The various members of this order are more different from each other than the members of any other order. You can specify some general features skeleton. The skull is mostly cone-shaped; the braincase, in comparison with the facial part and the nasal cavity, is smaller than in the animals we have already discussed; individual bones do not fuse as early and closely as in those. The spinal column usually consists of 7 cervical vertebrae, 12-15 vertebrae bearing the ribs, 4-6 lumbar, 2-7 sacral and various numbers caudal, since the tail is either completely invisible from the outside or underdeveloped, or reaches extremely large sizes. The clavicle, with the exception of a few species, always exists; the structure of the fore and hind limbs, on the contrary, is very diverse. The brain is characterized by insignificant development: the hemispheres of the cerebrum are almost completely flat, which does not speak in favor of marsupials and explains the rather insignificant degree of development of their mental abilities. The stomach in species that feed on meat, insects and fruits is simple and rounded, in others it is noticeably elongated; the intestine can also have a very diverse structure. The teeth of marsupials are similar to the teeth of more developed mammals in only one respect: they are partially replaceable. In all other respects they differ very significantly. Most marsupials are especially distinguished by a significant number of teeth. Fangs, which are very large in meat-eating animals, are poorly developed in plant-eating animals, and in many they are completely absent. The number of incisors is usually not the same in both jaws; false-rooted with two roots; true molars are acutely tuberculate or equipped with folds of enamel various shapes. All representatives of the order have the same structure of the genital organs and the presence of bursa bones. In the female, they strengthen the abdominal wall and protect the young in the pouch from the pressure of the mother's abdominal innards. The pouch contains the nipples of the mammary glands, to which cubs born prematurely are sucked. The bursa may be a real pocket or may be underdeveloped, forming two leathery folds, or even be in its rudimentary state. Cubs are born in a state unlike any other higher mammal. They are small, hairless, blind and have only rudimentary limbs. After birth, they attach themselves to one of the nipples, which usually look like a long conical wart and soon grow noticeably. Then they quickly develop, sometimes leave the nipple and crawl out of the bag.
From the day of conception until the baby can stick its head out of the pouch, the gigantic kangaroo takes about 7 months; from this time until he leaves the pouch for the first time, there are about 9 more weeks, and for the same amount of time the young kangaroo then lives partly in the pouch, partly outside. The number of cubs can be very significant*.
* The size of the cubs at birth does not exceed 0.5-3 cm. One litter can contain from one to 25 (a record among mammals!) newborns.
As already noted, marsupials currently inhabit Australia and some adjacent islands, as well as South and North America. In America there are only representatives of one family, mainly in its southern part**.
* * The diversity of marsupial life forms in South America throughout most of the Cenozoic was almost equal to that in Australia. In addition to possums and caenolests that have survived to this day, large predators and small herbivorous analogues of rodents lived here. Most of the continent's marsupials did not survive the placental invasion; but when the land connection between North and South America was re-established, some opossums re-colonized North and Central America.
Different kinds marsupials have little in common in their way of life: some of them are predators, others feed on plants; many live on the ground, others in trees, some even in water at times; Most are nocturnal animals, some, however, are active during the day. Of the carnivores, many run and climb deftly, and of those that feed on plants, some are fast and resilient in running. However, one cannot help but notice that even the most advanced of marsupials do not reach the mobility of more developed mammals. The kangaroo is inferior to the deer or antelope, and the wombat to even the most clumsy rodent. The same applies to the mental abilities of marsupials; and in this respect they cannot be compared with other animals. Their external senses alone are perhaps at the same level as those of other mammals; their understanding, on the contrary, is always insignificant. Each marsupial, in comparison with the approximately corresponding higher mammal, is a stupid creature, not amenable to either training or education. It is impossible to raise a dog with almost a human mind from a marsupial wolf. The imperfection, rudeness and clumsiness of marsupials is especially clearly revealed in their morals and habits.
Marsupial food in highest degree diverse. All species that correspond to predators pursue other animals, eat shellfish, fish and other prey thrown up by the sea, or the carrion of land animals; smaller species hunt birds, insects and worms. Herbivores feed on fruits, leaves, herbs and roots, which they pick or pluck. Predatory marsupials sometimes cause harm and annoyance by chasing herds, climbing into chicken coops at night and causing other troubles. Europeans exterminate marsupials as quickly as possible, without any specific purpose, but only to satisfy the unbridled passion for hunting. In this case, the meat and skin of only a few species are used, and the rest are not needed for anything.
Life of animals. - M.: State Publishing House of Geographical Literature. A. Brem. 1958.
See what “Order Marsupials” is in other dictionaries:
Marsupial mammals, with the exception of American opossums, are common on the Australian mainland, New Guinea and nearby islands. This order includes about 200 species from 9 families. Among marsupials there are insectivores,... ... Biological encyclopedia
a subclass of primitive mammals that combine the features of mammals and reptiles. In this subclass there is a single infraclass cloacal, contrasted with the infraclasses placentals and marsupials from the subclass Beasts. Modern species of primitive animals form only one order - monotremes. First beasts are a small group of species common in the Australian region. According to a number of characteristics, the subclass of the first beasts and the infraclass cloacal are considered the most archaic and primitive among the infraclasses of mammals. Unlike other mammals, the first beasts reproduce by laying eggs, but more than half of the development period of the embryo passes in the female genital tract. Thus, the laid eggs contain an already sufficiently developed embryo and we can talk not only about oviparity, but also about incomplete viviparity. Females, instead of nipples, have zones of mammary glands from which the offspring licks milk. There are no fleshy lips (effective for sucking). In female echidnas, only the left half of the reproductive apparatus functions (like in birds). In addition, like birds and reptiles, they have only one passage. They have fur, but homeothermy (maintaining body temperature at a constant level) is incomplete, body temperature varies between 22-37 ° C. Nowadays, all types of cloacal animals live in Australia, New Guinea and Tasmania. Echidnas look like a small porcupine, as they are covered with coarse hair and quills. Maximum length the body is approximately 30 cm. Their lips have a beak-like shape. Echidnas' limbs are short and quite strong, with large claws, allowing them to dig well. Echidnas have no teeth and a small mouth. The food consists of termites and ants, which echidnas catch with their long sticky tongue, as well as small invertebrates, which echidnas crush in their mouths, pressing their tongues to the roof of their mouth. Behavior. Lifestyle: For most of the year, with the exception of the mating season in winter, echidnas live alone. Each individual protects its own territory, where it hunts and does not have a permanent shelter. Echidnas swim well and cross large bodies of water. Echidnas have keen eyesight. In case of any threat, echidnas quickly hide in thickets or rock crevices. In the absence of such natural shelters, echidnas quickly burrow into the ground and only a few needles remain on the surface. Three weeks after copulation, the female echidna lays one soft-shelled egg and places it in her pouch. “Incubation” lasts ten days. After hatching, the baby is fed milk (monotremes do not have nipples), and remains in the mother’s pouch for 45 to 55 days, until its needles begin to grow. After this, the mother digs a hole for the cub, in which she leaves it, returning every 4-5 days to feed with milk. Platypus- a waterfowl mammal of the order Monotreme, living in Australia. Appearance: The body length of the platypus is 30-40 cm, the tail is 10-15 cm, it weighs up to 2 kg. Males are about a third larger than females. The body of the platypus is squat, short-legged; the tail is flattened, similar to the tail of a beaver, but covered with hair, which noticeably thins with age. Fat reserves are deposited in the tail of the platypus. Its fur is thick, soft, usually dark brown on the back and reddish or gray on the belly. The head is round. In front, the facial section is extended into a flat beak about 65 mm long and 50 mm wide. The beak is not hard like that of birds, but soft, covered with elastic bare skin, which is stretched over two thin, long, arched bones. The oral cavity is expanded into cheek pouches, in which food is stored during feeding. Down at the base of the beak, males have a specific gland that produces a secretion with a musky odor. The platypus has five-fingered feet, adapted for both swimming and digging. The membrane on the front paws protrudes in front of the toes. The membranes on the hind paws are much less developed; The hind legs act as a rudder in the water, and the tail serves as a stabilizer. There are no auricles. The eyes and ear openings are located in grooves on the sides of the head. Reproductive system: females differ from those of placental animals. Its paired ovaries are similar to those of a bird or reptile; Only the left one functions, the right one is underdeveloped and does not produce eggs. 1-3 eggs per hole. (10 days) clogs the entrance to the hole with an earthen plug. Marsupials - infraclass of mammals. Among marsupials there are insectivorous, carnivorous and herbivorous forms. Their body length, including tail length, can range from 10 cm (Kimberley marsupial mouse) to 3 m (great gray kangaroo). Marsupials are more complexly organized animals than monotremes. Their body temperature is higher (on average - 36°). All marsupials give birth to live young and feed them with milk. However, compared to higher mammals, they have many ancient, primitive structural features that sharply distinguish them from other animals. First characteristic marsupials - the presence of so-called marsupial bones (special pelvic bones that are developed in both females and males). Most marsupials have a pouch for bearing young, but not all have it developed to the same extent; There are species that do not have a pouch. Most primitive insectivorous marsupials do not have a “finished” pouch - a pocket, but only a small fold delimiting the milky field. This is the case, for example, in numerous marsupial mice. The yellow-footed marsupial mouse, one of the most archaic marsupials, has only a slight raised skin, like a border around the milky field. In kangaroos, whose pouch is more perfect, it opens forward towards the head, like an apron pocket. The second characteristic feature of marsupials is the special structure of the lower jaw, the lower (posterior) ends of which are curved inward. The coracoid bone in marsupials is fused with the scapula, like in higher mammals, this distinguishes them from monotremes. The structure of the dental system is an important classification feature of the marsupial order. Based on this feature, the entire order is divided into 2 suborders: multi-incisor and two-incisor. The number of incisors is especially large in primitive insectivorous and carnivorous forms, which have 5 incisors at the top and 4 at the bottom in each half of the jaw. In herbivorous forms, on the contrary, there is no more than one incisor on each side of the lower jaw; their fangs are absent or underdeveloped, and their molars have blunted tubercles. The structure of the mammary glands of marsupials is characteristic; they have nipples to which newly born babies are attached. The ducts of the mammary glands open at the edge of the nipples, as in monkeys and humans, and not into the internal reservoir, as in most mammals. The koala is a medium-sized animal with a dense build: its body length is 60-82 cm; weight from 5 to 16 kg. The tail is very short and invisible from the outside. The head is large and wide, with a flattened “face”. The ears are large, rounded, covered with thick fur. The eyes are small. The bridge of the nose is hairless and black. There are cheek pouches. The koala's hair is thick, soft, and durable; on the back the color varies from light gray to dark gray, sometimes reddish or reddish, the belly is lighter. The koala's limbs are adapted to climbing - large and index fingers the fore and hind limbs are opposed to the rest, which allows the animal to grasp the branches of trees. The claws are strong and sharp, capable of supporting the weight of the animal. There is no claw on the big toe of the hind limbs. The brood pouch in females is well developed and opens at the back; There are two nipples inside. Koalas are found in eastern Australia - from Adelaide in the south to Cape York Peninsula in the north. Koalas inhabit eucalyptus forests, spending almost their entire lives in the crowns of these trees. During the day, the koala sleeps (18-22 hours a day), sitting on a branch or in the forks of branches; At night it climbs trees, looking for food. Even if the koala is not sleeping, it usually sits completely motionless for hours, grasping a branch or tree trunk with its front paws. The koala receives all the necessary moisture from the leaves of eucalyptus trees, as well as from dew on the leaves. They drink water only during periods of prolonged drought and during illness. To compensate for the deficiency of minerals in the body, koalas eat soil from time to time. During the breeding season, koalas gather in groups consisting of an adult male and several females. Mating takes place on a tree (not necessarily eucalyptus). Pregnancy lasts 30-35 days. There is only one cub in the litter, which at birth is only 15-18 mm long and weighs about 5.5 g; occasionally twins. The cub remains in the pouch for 6 months, feeding on milk, and then “travels” for another six months on the mother’s back or stomach, clinging to her fur. Kangaroos ( Macropodidae) - a family of marsupial mammals. includes herbivores adapted to move in leaps. It includes animals of medium and large size - wallabies, wallaroos and kangaroos. Adult animals have a body length from 30 to 160 cm; weigh from 0.5 to 90 kg. The head is relatively small, the ears are large. In all genera, with the exception of tree wallabies ( Dendrolagus) and philanderers ( Thylogale), the hind legs are noticeably larger and stronger than the front ones. Front legs small sizes and have 5 fingers; rear - 4 ( thumb usually atrophied). Like other two-incisor animals, the second and third toes on the hind legs of a kangaroo are fused. Limbs are plantigrade. Most species move by hopping on their hind legs. Important role When a kangaroo jumps, the elastic Achilles tendons play, which act like springs during a running jump. The kangaroo's tail is usually long, thick at the base, and not prehensile. During a jump, it serves as a balancer, and in a calm state it is used as additional support. Kangaroos usually stand upright, resting on their hind legs and tail. The teeth are adapted to eating plant foods - wide incisors, small canines and a diastema in front of large premolars; teeth 32-34. The stomach is complex, divided into compartments where plant fiber is fermented under the influence of bacteria. A well-developed brood pouch opens forward. Of the 4 nipples in females, only two usually function. Kangaroos breed once a year. Pregnancy is short.
46 INSECTIVORE(Insectivora), an order of primitive mammals. Usually small animals, varied in appearance and lifestyle. The five-fingered limbs are equipped with claws. The muzzle is elongated and pointed, with an elongated nose protruding far beyond the skull. Teeth so-called insectivorous type. The incisors are often long, forming something like pincers; canines are always present, but usually resemble adjacent incisors or premolars; molars are covered with sharp tubercles. Eyes and ears are usually small and inconspicuous. The brain for placental mammals is primitive; The cerebral hemispheres are smooth, without grooves. Insectivores are widespread throughout the globe, but are absent from Australia and much of South America. Modern species are divided into four clearly distinct superfamilies: 1) tenrecs (Tenrecoidea), which include tenrecs, golden moles and otter shrews; 2) hedgehogs (Erinaceidea), combining hedgehogs and gymnurs; 3) shrews (Soricidea): shrews, muskrats, moles and shrews; 4) jumpers (Macroscelididea). Some biologists place the tupai in the latter subfamily, considered primates in other systems. Appearance Insectivores are quite diverse. Burrowing species, such as moles, are covered with soft, velvety fur, the pile of which lies in any direction, which facilitates movement through tight underground passages. These animals' two strong, shovel-shaped front paws are excellent for digging. Hedgehogs are covered with spines, and the African otter shrew ( Potamogale), leading a mainly aquatic lifestyle, the tail is long and laterally flattened. Other aquatic forms, shrews and muskrats, also have well-defined adaptations to life in water - fringes or ridges of coarse hair on the hind legs and tail help them swim. The jumpers living in Africa are distinguished by their very long hind limbs and tail, which help them make powerful jumps to escape their pursuers. The main food of the representatives of the order consists of insects and their larvae, worms and other small invertebrates. Hedgehogs often eat various fruits, and the otter shrew eats small fish and crustaceans. Some miniature species have an insatiable appetite, and often the amount of food they eat per day exceeds their own body weight. Insectivores are not as fertile as, say, rodents, but up to 20 embryos can be found in the body of a female tenrec.
48. Order Primates. A special place in the system of the animal world. Order Primates Of all mammals, primates are distinguished by the greatest diversity and richness of forms. Primates have a well-developed five-fingered, grasping limb adapted for climbing tree branches. All primates are characterized by the presence of a clavicle and complete separation of the radius and ulna, which provides mobility and a variety of movements of the forelimb. The thumb is mobile and in many species can be opposed to the other fingers. The terminal phalanges of the fingers are equipped with nails. In those forms of primates that possess claw-like nails or have claws on individual digits, the thumb always bears a flat nail. When moving on the ground, primates rest on their entire foot. Arboreal life in primates is associated with a reduction in the sense of smell and increased development of the organs of vision and hearing. The eyes of primates are more or less directed forward, and the orbits are separated from the temporal fossa by a periorbital ring (tupai, lemurs) or a bony septum (tarsiers, monkeys). On the muzzle of lower primates there are 4 - 5 groups of tactile hairs - vibrissae, in higher primates - 2 - 3. The active life and variety of functions of the forelimbs led to the strong development of the brain in primates, and in connection with this, an increase in the volume of the cranium and, accordingly, a reduction in the facial region skulls But well-developed cerebral hemispheres with abundant grooves and convolutions are characteristic only of higher primates. The lower representatives of the order have a smooth brain or have few grooves and convolutions. Primates mainly eat a mixed diet with a predominance of plants, and less often are insectivores. Due to their mixed diet, their stomach is simple. There are four types of teeth - incisors, canines, small (premolars) and large (molars) molars; molars with 3-5 cusps. In primates, there is a complete change of teeth - milk and permanent. Significant variations are observed in the body sizes of primates - from small mouse lemurs to gorillas 180 cm tall and above. The hair coat in primates is thick, with undercoat in prosimians; in most monkeys it is poorly developed. The tail is long, but there are short-tailed and tailless forms. Primates reproduce all year round, the female usually gives birth to one (in lower forms - sometimes 2-3) cub. As a rule, primates live in trees, but there are terrestrial and semi-terrestrial species. About 200 species of modern primates are known. They are united in 57 genera, 12 families and 2 suborders - prosimians (Prosimii) and monkeys (Anthropoidea). In many anatomical and biological traits, man belongs to the higher primates, where he forms a separate family of people (Hominidae) with the genus Homo and one species - modern intelligent man (H. sapiens). The practical importance of primates is very great. As living and funny creatures, monkeys have always attracted human attention. They were hunted and sold to zoos and for home entertainment. The meat of many monkeys is still eaten by the aborigines. IN last years Primates are becoming increasingly important in biological and medical experiments. Semi-monkeys (PROSIMII) (Suborder) This suborder includes the most primitive representatives of primates - tupai, lemurs, tarsiers. Tupai and lemurs are sometimes grouped together as strepsirrhine primates, which have comma-shaped nostrils that open onto the bare tip of the nose. The upper lip of these primates is smooth, motionless and hairless. On the contrary, tarsiers and monkeys form a group of haplorine primates, with nostrils more rounded, bordered by the walls of the nose and opening onto a mobile, with a developed muscular layer, and hairy upper lip. The suborder of prosimians includes 6 families, 21 genera and about 50 species with a large number of subspecies. HIGHER HUMAN-LIKE PRIMATES (ANTHROPOIDEA) (SUBORDER) The suborder of higher primates includes broad-nosed monkeys (Platyrrhina), or American monkeys, and narrow-nosed monkeys (Catarrhina), or African-Asian monkeys. This division is based on the difference in the structure of their nose. In most New World monkeys, the cartilaginous nasal septum is wide and the nostrils are widely separated and outward facing. Old World monkeys have a narrower nasal septum and nostrils, like those of humans, point downward. But it is more correct to talk about the degree of severity of this feature, since the thickness of the nasal septum and the position of the nostrils can vary in different forms of broad-nosed and narrow-nosed monkeys. All primates have flat nails on their fingers (marmosets have claw-shaped nails); the eyes are facing forward, and the orbit is completely separated from the temporal fossa by a bony septum; the brain, with the exception of marmosets, is rich in grooves and convolutions; the upper incisors are not separated by a space. Primates are characterized by a reduction of the olfactory apparatus and special tactile organs on the face, where only three pairs of vibrissae are preserved - supraorbital, maxillary and mental. The reduction of vibrissae is associated with the progressive development of tactile skin ridges on the palmar and plantar surfaces. Only in Oedipus marmosets and, to a greater extent, in nocturnal monkeys, areas of skin without ridges are still found on the palms and soles. In other lower and higher primates, the palmar and plantar surfaces are completely covered with skin ridges, just like in humans. The suborder has 3 superfamilies: Ceboidea, Cercopithecoidea and Hominoidea. All higher primates in Kr. book