The topic of our lesson: “Class Mammals or Animals.” The purpose of the lesson is to provide a brief description of the class Mammals and its four orders: Monotremes, Marsupials, Insectivores and Chiroptera.

2. Characteristics of the class Mammals

In the previous lesson, we completed the conversation about birds. Now let's make a brief description of the class Mammals. The class got its name because females feed their young with milk (Fig. 1). Milk is produced by the mammary glands, which are derived from the sweat glands.

Rice. 1. Feeding the cubs

Viviparity, feeding with milk and caring for offspring ensures better safety of the young under a wide variety of circumstances, but all this is possible only with a small number of cubs.

Mammals, or animals, appeared 160–170 million years ago. The ancestors of mammals were about the size of a rat, and they most likely fed on insects.

Just like birds, mammals have a constant body temperature; they are warm-blooded animals (Fig. 2). Mammals are characterized by hair. If the feathers of birds are similar in structure and development to the scales of reptiles, then the hair of mammals is a unique formation.

Rice. 2. Warm-bloodedness allows animals to survive at low temperatures

The appearance and size of mammals are very diverse. There are 2 pairs of 5-fingered limbs. The cervical spine, consisting of 7 vertebrae, connects the head to the torso very movably. On the upper and lower jaws there are specialized teeth, that is, teeth that differ in structure and function.

All mammals are characterized by a high level of development of the nervous system, the cerebral cortex and sensory organs are especially developed.

The circulatory system is closed, the heart is four-chambered. Blood moves through two circulation circles; venous and arterial do not mix (Fig. 3).

Rice. 3. Mammalian circulatory system: systemic and pulmonary circulation

There are more than 5.5 thousand species of modern mammals. They are widely distributed throughout the globe. They live in a wide variety of conditions - at the Earth's poles, in soil, in sea and fresh water, some have mastered flight.

The class mammals is divided into subclasses: Oviparous, or primal beasts, and True beasts.

3. Subclass Oviparous

The subclass Oviparous, or Primordial Beasts, has only five species, among them the platypus, 2 types of echidnas and 3 types of proechidnas (Fig. 4). They live in Australia, Tasmania and New Guinea.

Rice. 4. Primal beasts

This is a very ancient order of mammals with many very primitive characteristics. Body temperature is not constant - from 22 to 25 degrees for the platypus and about 30 degrees for echidnas.

They reproduce by laying eggs. They incubate their eggs, like the platypus, or carry them in a leathery pouch on their belly, like the echidna. The eggs are covered with a keratinized shell.

The body of the platypus is covered with thick hair, the head ends in a keratinized lamellar beak without teeth. The front and rear limbs of the platypus have leathery membranes, with the help of which it swims and dives. Adult platypuses feed on a variety of aquatic invertebrates (Figure 5).

Rice. 5. Platypus

The body of the echidna (Fig. 6) is covered with needles, the beak is tubular. The female lays eggs in a burrow and carries them in a leathery pouch on her belly for about 9–10 days. Sharp claws are used by monotremes for digging burrows. All representatives of the order are rare animals and are subject to protection.

Rice. 6. Echidna

4. Subclass Real animals

Order Marsupials (Fig. 7). There are about 250 species of modern marsupial mammals. They live in Australia, New Guinea and nearby islands. Several species are also found in America.

Rice. 7. Marsupials

The detachment received its name for the presence of a special leathery fold on the belly in the form of a pocket or bag in which newborns are placed. Gestation periods in marsupials are very short. The cubs are born small, blind, helpless and virtually underdeveloped (Fig. 8).

Rice. 8. Newborn marsupial

Their further development takes place in the bag. In large species of kangaroos, the length of a newborn is only about 25 mm, in small species of marsupials it is only about 7 mm. The weight of a newborn calf in various representatives of the order is from 0.6 to 5.5 g.

In the pouch, the baby attaches itself to the nipple of the mammary gland and spends there for up to several months. Probably the most famous of the marsupials, the kangaroo (Fig. 9) feeds on plant matter and moves by jumping.

Rice. 9. Kangaroo

The convergence of some marsupials with the higher animals well known to us is surprising. Thus, the marsupial mole (Fig. 10) lives in the soil, digs holes, and feeds on worms and insects. The marsupial cat is an arboreal predator (Fig. 11).

Rice. 10. Marsupial mole

Rice. 11. Marsupial cat

Despite the great external similarity, they are completely unrelated to ordinary cats and moles. The marsupial koala bear lives on eucalyptus trees and feeds exclusively on their leaves (Fig. 12).

Rice. 12. Koala

The North American opossum, roughly the size of a cat, feeds on both animal and plant matter. Its close relative, the water possum, has leathery webbed feet, swims and dives well, and feeds on small fish and aquatic invertebrates (Fig. 13).

Rice. 13. Possum

5. Placental, or Higher animals

They are characterized by the presence of a placenta - a special organ that serves to nourish the developing embryo - and the birth of relatively developed young (Fig. 14).

Rice. 14. Higher beasts

Despite this name, representatives of the order can feed on both insects and other various small animals. Representatives of the order are animals of medium and small size, with an elongated muzzle ending in a proboscis (Fig. 15).

6. Order Insectivores

Rice. 15. Insectivores

This order is considered ancient; all insectivores, except hedgehogs, have short hair. They are very widespread, absent only in Australia, Antarctica and South America.

The total number of species of insectivores is about 400. Insectivores include hedgehogs, moles, shrews, muskrats and others. The largest representative of the order is the muskrat (Fig. 16), up to 22 cm long, with a long, laterally compressed scaly tail.

Rice. 16. Muskrat

The smallest representative is the tiny shrew, only up to 4 cm long (Fig. 17).

Rice. 17. Baby shrew

Hedgehogs live in deciduous and mixed forests, in forest-steppe and steppe regions of Europe. The back and sides of the hedgehog are covered with sharp spines; at the moment of danger, it curls up into a ball (Fig. 18).

The animal's paws are equipped with sharp claws. It is active at twilight and at night, feeding on various invertebrates, as well as frogs, lizards, snakes, and small birds. Capable of destroying nests. Hedgehogs destroy many agricultural pests, as well as poisonous snakes, so they can benefit humans.

Rice. 18. Hedgehogs

In winter, hedgehogs hibernate; in spring, the female gives birth to 3 to 8 cubs (Fig. 19). Hedgehogs become sexually mature in the 2nd year of life. The European hedgehog can be the host of ixodid ticks, a carrier of diseases dangerous to humans and domestic animals. There are up to 3 thousand ticks on one hedgehog.

Rice. 19. Baby hedgehogs

The muskrat has adapted to an aquatic lifestyle (Fig. 20). Its hind limbs have swimming membranes. The coat is thick, dense with a soft undercoat. The animal hunts at night and at dusk and lives near water in burrows.

Rice. 20. Muskrat

The muskrat feeds on both plant and animal food, which it finds in the water. The muskrat breeds in the spring, with litters ranging from 1 to 5 cubs, they grow quickly. At the age of one and a half months they are able to leave the nest and lead an independent lifestyle. The muskrat is a rare species; in many areas it has been replaced by the introduced muskrat.

7. Order Chiroptera

It includes about 1200 species, the second largest order of mammals after rodents (Fig. 21). Systematically, they are close to insectivores. Chiropterans have mastered the air; they are capable of long flapping flight.

Rice. 21. Chiroptera

They live almost all over the world, with the exception of the polar regions. The largest representatives with a wingspan of up to 180 cm (Fig. 22) live in the tropics of Asia, Australia and Africa and belong to the suborder Bats. They feed on juicy fruits.

Rice. 22. Fruit bats

Smaller representatives of bats belong to the suborder of bats. All bats are united by the presence of a leathery membrane that forms the wing between the fore and hind limbs. The tail is also usually covered with a membrane.

The first toe of the forelimbs is free and is used for climbing cave walls, tree bark, and so on. When at rest they hang horizontally or vertically upside down (Fig. 23). In this position they sleep, give birth to cubs, and some spend the winter in this position.

Rice. 23. Position in space

During sleep, body temperature drops significantly, blood circulation and breathing slow down. Bats are active at dusk and at night. Most species catch insects in flight, but some feed on soft fruits, fish, or even the blood of warm-blooded animals.

Vision in bats is poorly developed, but they are well oriented in the dark. The fact is that bats are capable of so-called echolocation. In flight, they constantly emit high-frequency sounds, ultrasounds. Sounds reflected from obstacles are captured by the large and complexly arranged ears of animals.

By the nature of the reflected sound, bats are able to calculate the distance to objects, and they never bump into obstacles. Most bats winter in warm countries, while a minority spend the winter in shelters. At the same time, their body temperature can drop to almost 0 degrees.

Bats breed in the summer; females, as a rule, give birth to one, naked and blind cub. Having clung to the mother’s body, covered with warm fur, it does not let go of her for up to 2 months, even during hunting (Fig. 24).

Rice. 24. Baby Bat

By exterminating a large number of insects, pests and mosquitoes, bats bring tangible benefits to humans; they need to be attracted to human habitation, creating shelters for them and protecting their habitats.

Origin of mammals

Among the reptiles of the subclass Animal-like, the order Animal-toothed was formed by the Permian period. These animals, instead of the identical teeth characteristic of reptiles, had incisors, fangs and molars (Fig. 25).

Rice. 25. Structure of teeth

The structure of their jaws resembled the structure of the jaws of mammals. By the end of the Triassic period, the hyper-toothed animals were completely replaced by other reptiles.

All their large representatives died out, but already in the Triassic period some group of small species of mammals, probably living in dense thickets, gradually acquired the features of a more aggressive organization and gave rise to mammals.

Mammal records

The body length of mammals ranges from 4 centimeters for the dwarf shrew to 33 meters for the blue whale (Fig. 26, 27). Body weight – from 1.5 grams to 150 tons.

Rice. 26. Pygmy shrew

Rice. 27. Blue whale

The slowest mammals are sloths (Fig. 28), they move only when absolutely necessary, and still slowly, hence the name.

Rice. 28. Sloth

The fastest mammal is the cheetah; at short distances it can reach speeds of up to 115 km/h (Fig. 29).

Rice. 29. Cheetah

Bloodthirsty hedgehogs

Hedgehogs bring tangible benefits by destroying agricultural pests, including in gardens and vegetable gardens. An ordinary hedgehog eats up to 200 grams of insects in one night.

In New Zealand, in the absence of natural predators, they themselves have turned into pests, destroying local insects, shellfish and ruining bird nests. The example of hedgehogs clearly shows how alien the principle of humanity is to nature.

Hedgehogs love to eat small reptiles, including snakes, even poisonous ones. They are reliably protected from bites by their needles and often begin to eat the snake alive from the middle of the body or even from the tail.

Vampires

Now we will talk about vampires, but not the ones in the movies, but the real ones, these are 3 types of bats that live in tropical America. They feed on the blood of any warm-blooded animal.

Their saliva contains substances that relieve pain and prevent blood clotting. Bleeding after a bite can last up to 8 hours, but this is not the main problem.

The fact is that vampires carry rabies and other dangerous infections. Vampires themselves do not die from rabies; they are the only mammals that are immune to this virus. Vampires also brought benefits: an anti-stroke drug was created based on their salivary enzyme, which prevents blood clotting in mammals.

7. Discuss with friends and family the importance of mammals in nature and agriculture.

The class Mammals are divided into two subclasses: Oviparous and Viviparous. The subclass Viviparous includes marsupials and placental mammals. This division is determined by the developmental characteristics of the embryos of these animals. What are these features? What animals belong to the above groups?

Oviparous animals (Prime Beasts) do not give birth to cubs, but lay eggs. They, like reptiles and birds, have a cloaca into which the ureters and ducts of the reproductive system open. Modern oviparous animals are represented by one order, including only a few species of animals. These are the platypus and echidnas (Fig. 51.1), living in Australia and on the islands closest to it.

The platypus is an animal the size of a small rabbit. He lives along the banks of reservoirs, where he digs minks, making a nest of grass in them. The front of the head resembles the beak of a duck (hence the name of the animal). It feeds on worms, crustaceans and mollusks, scouring the mud. Thanks to the membranes between the toes, the platypus swims well.

When the stuffed platypus was first brought to Europe, scientists decided that it was a fake - the duck’s beak was sewn to the body of some animal. They were even more surprised when it turned out that the platypus lays eggs like a reptile and incubates them like a bird for about 10 days. The surprises continued: it turned out that the baby platypus, after hatching from the egg, feeds on milk! But the female platypus secretes milk on her stomach not through her nipples, but as sweat. The cub simply licks it from the mother's fur. The babies stay in the mink for about four months and feed on their mother's milk, and then begin to live independently. Material from the site

The echidna, a resident of dry forests, looks like a hedgehog. In search of food (termites, ants and worms), the echidna digs the ground with strong claws and, with the help of long tongues and a sticky tongue, gets food for itself. A female echidna weighing about 5 kg lays one egg weighing less than 2 g. The egg, like those of reptiles, is covered in a leathery shell. The female puts the egg into a pouch formed by a fold of skin on her belly and carries it, warming it with her warmth, for about two weeks. From the egg, breaking the shell with an egg tooth, a naked, blind cub weighing 0.5 g emerges, which is fed in the mother’s pouch. In warm conditions, feeding on milk, it grows quickly. At 7-8 months, the cub already gets food on its own and looks quite adult - perhaps a little smaller than the mother.

Oviparous animals are warm-blooded. However, their body temperature is lower than that of other mammals and can vary from 25 °C to 35 °C depending on the ambient temperature.

On this page there is material on the following topics:

• Flatworms are oviparous or viviparous

• Egg-laying and everything about them

• What types of oviparous species are there?

• Amphibians are viviparous or oviparous

• Variety of reptiles

Questions about this material:

Oviparous and marsupial mammals.

Oviparous or primeval beasts - relict forms, the distribution of which is now limited to Australia and New Guinea. They are related to reptiles following signs:

1) laying large, yolk-rich eggs, which are then hatched in a pouch (in the echidna) or incubated (in the platypus);

2) shoulder girdle with coracoid;

3) cloaca.

Signs of mammals:

1) hair;

2) homeothermy (not yet perfect);

3) mammary glands;

4) heterogamety of males.

Marsupials give birth to underdeveloped young (short pregnancy), which are carried to term, fed with milk in a pouch or between the folds of skin on the abdomen. Currently they are found only in Australia and South America; only one low-specialized species, the North American opossum, spread throughout North America. Various marsupials were able to survive only where geographic isolation saved them from competition with placental mammals,

In Australia, there are known predators among marsupials ( marsupial wolf, marsupial marten), insectivores (marsupial mole, marsupial shrew, marsupial anteater marsupial flying squirrel), fruit- and leaf-eaters (tree kangaroos, koalas) and, finally, large herbivores (kangaroos). This adaptive radiation clearly demonstrates how in Australia specialized marsupials were able to master all those ecological niches, which on other continents turned out to be occupied by placentals.

68. Insectivores and chiroptera mammals.

In insectivores usually a long head and an elongated snout that ends in a proboscis. Their body is short. Some insectivores are covered with soft, silky fur, while others have hard spines. Many of them live underground, some in water and some in trees.

Some insectivores spend the winter in hibernation, while others continue their active lifestyle in winter under the snow or in water under ice, or in underground passages. Many types of insectivores are useful for Agriculture. They exterminate harmful insects, their larvae, worms, snails and even small rodents. There are species that produce valuable varieties of fur.

Insectivores are found mainly in temperate countries northern hemisphere, there are especially many of them in China. In South America and Australia there are no insectivores at all.

Distinctive chiropteran trait- these are peculiar wings that were formed from the forelimbs. Between their very elongated fingers they have a thin leather membrane stretched, which is also adjacent to the sides of the body. The same membrane is stretched between the hind legs and the tail. Thanks to their wings, bats appear to be quite large animals, but in fact, many of them belong to the smallest mammals.

U bats remarkably developed sense of touch. Even when flying, they are guided not by sight, but mainly by touch. Scientists did the following experiments: they stretched many threads along and across the room and let a bat fly, and it flew without touching a single thread.

Then they covered her eyes and even her ears with English plaster and let her fly again. Blinded and deaf, the bat flew between the threads with the same speed and confidence as before, and did not touch a single thread.

Bats, with the exception of some species, hibernate in winter. Before this they become very fat; fat lies in layers between the muscles and skin and on the insides. There is so much fat that in some species its weight exceeds the weight of the animal itself. Due to this fat, as well as other body substances, bat feeds during hibernation. During this time, she loses a fifth or sixth of her weight.

69.Lagomorphs and rodents.

Gnawing Mammals- a group that includes mice, rats, rabbits - are extremely lucky animals, found in almost all habitats except the seas. Most of them live on the ground, although there are many rodents - such as squirrels - that are good at climbing trees and find refuge there. Others - like beavers and some voles - live around fresh water or even in it. Many people use holes only as shelters, but mole rats and similar species are adapted to life underground and almost never come to the surface.

Lagomorpha - hares, rabbits, haymakers - live a life similar to rodents. Main representatives. The order of rodents (1,600 species) is the most numerous among mammals; it includes several families of animals. A group of squirrels (377 species) with marmots and beavers. Group of porcupines (188 species) with guinea pigs and chinchillas. A group of mice (1137 species) with rats and hamsters. The order Lagomorpha (58 species) includes rabbits, hares, and pikas. Teeth and jaws. Rodents have a pair of large incisor teeth at the top and bottom.

Reproduction. Many gnawing mammals produce numerous offspring. In fact, they are not so often and not so large quantities are multiplying. While some animals produce 17 young at once, for rodents and lagomorphs the most typical number is 4. However, the young themselves are capable of reproducing already in early age. In species such as mice, pregnancy lasts only a few weeks, and the new generation can produce a litter on its own in less than a year. Rabbits reproduce no less quickly. Dwellings Some rodents find refuge in hollows. Others construct a nest from branches, like some squirrels, or from grasses and bark, like field hamsters. Rodent houses are generally not made very skillfully, but Australian rats build large waterproof structures. Such dwellings may have several compartments, including a pantry and a latrine. But the best land-based homes are created by beavers.

70.Carnivorous mammals.

The order of carnivorous mammals unites the most different kinds animals - from a huge lion to a tiny weasel. In this detachment we meet a cat and a hyena, a civet, a dog, a bear and a marten.

But all these various animals are armed with lips and claws for attacking other animals whose meat they feed on. All of them are carnivorous predators, and the better their body is adapted to meat food, the better their so-called carnivorous teeth are developed and the fewer teeth remain behind the carnivores. In the family of bears that eat and plant foods, the carnivorous tooth is almost indistinguishable from the tuberculate teeth lying behind it, with blunt tubercles and a wide chewing surface. Dogs have two teeth behind the carnivorous teeth in the upper and lower jaws. Cats have only one small molar behind the carnivorous or carnivorous tooth in the upper jaw, and this is the last tooth in the lower jaw. Due to the greater development of the chewing muscles, the skulls of predatory mammals usually have strongly protruding ridges. The brain is well developed, the hemispheres are covered with convolutions. In some species, the anal glands secrete a foul-smelling fluid in the anal region. This liquid serves to protect against enemies or to lure prey. Sometimes the glands secrete a fatty mass to lubricate the fur. Both in general body composition and gait carnivorous mammals very different. Among them there are plantigrade walkers, digitigrade walkers and transitional ones between both. Most species have a well developed tail. Carnivores run quickly on the ground, many of them are excellent at climbing trees; some species have adapted to life in water, and as a result their general appearance has changed.

The most valuable fur-bearing animals belong to the order of carnivores.

71. Pinnipeds and cetaceans.

Their body shape is streamlined, torpedo-shaped.
The skin has no fur, and there are no skin glands.
The forelimbs are modified into flippers, and the hind limbs are absent.
Cetaceans move with the help of a powerful tail with a large caudal fin. Most noticeable external difference whale from fish - this is the horizontal position of the caudal fin. It allows cetaceans to move along a wavy line, which provides communication with atmospheric air.
They breathe, like all animals, with the help of their lungs. In one breath, the lungs of whales are filled with air in a volume of up to 5,000 to 14,000 liters, which allows the animals to stay under water from 15 to 90 minutes.
Cetaceans see relatively well, and their hearing is even better developed. Cetaceans have the ability to echolocate and easily navigate even great depth. Many cetaceans migrate, swimming up to 10,000 km.
A layer of fat 18-50 cm thick accumulates under the skin of cetaceans. ensuring constant body temperature and reducing specific density.

Pinnipeds: Animals of medium and large size: from 1.2 to 6 m long and weighing from 40 to 3500 kg.
The body is elongated, fusiform, streamlined, with a relatively small head and thick neck.
The teeth are sharp and serve to grasp prey; they feed on fish, crustaceans, and mollusks.
The ear openings close when immersed in water.
The limbs are short, their shoulder and thigh sections are hidden in the body, and the paws visible from the outside have been transformed into something like fins - flippers. The front flippers, like the paired fins of a fish, control turns, and when moving on the ground or ice, they allow them to crawl, clinging to uneven ground with their claws. The hind limbs always remain extended back, in their outline representing some semblance of a fish tail, they do not take part in movement on land, and in water they serve as a powerful organ of movement.
They have hair. IN hairline there is a transition from thick fur with dense down in fur seals to sparsely spaced coarse hair - in walruses.
The subcutaneous layer of fat is about 10 cm.
Pinnipeds are semi-aquatic mammals. Most They spend time in the water, where they get their food, rest on land, reproduce, and feed their offspring.

72. Proboscis, artiodactyl and equid mammals.

All equids have a particularly developed third digit. They rely on it when walking.

Even-toed ungulates do not have fangs, or their fangs are poorly developed, there are special folds of enamel on the molars, and there are almost always incisors in both jaws. The stomach of equids is simple, and not complex, like that of ruminants. The liver does not have a gallbladder.

This whole detachment falls into three families: three-toed rhinoceroses, one-toed horses and tapirs, which have four toes on the forelimbs and three toes on the hind limbs.

Each leg has either two toes - the third and fourth, or four toes, but then the third and fourth are more developed than the lateral ones - the second and fifth. To better understand the large number and variety of species of these animals, they are divided into groups. There are two groups: 1) non-ruminant, or porcine-like; In addition to the two main fingers, they have a relatively well-developed second and fifth; 2) two-hoofed animals, or ruminants; these second and fifth fingers are underdeveloped or absent at all. Ruminants differ from other ungulates and from all other mammals in that they chew their food twice (rumination).

The group of pigs includes pigs and hippopotamuses; to the group of ruminants - the rest numerous species artiodactyls.

All artiodactyls feed exclusively or mainly on plant foods.

Marsupials (lower animals) (Metatheria) Marsupial mammals, with the exception of American opossums, are common in Australia and the surrounding islands. Their placenta is absent or weakly expressed, the cubs are born after short period uterine development is poorly developed. There are about 250 species of marsupials, among them there are insectivorous, predatory and herbivorous forms.

Kangaroo is a marsupial

Their body length, including tail length, ranges from 10 cm (Kimberley marsupial mouse) to 3 m (great gray kangaroo). Marsupials are more highly organized animals than monotremes: their body temperature is higher (on average 36 oC). Characteristic marsupials - the presence of so-called marsupial bones (special pelvic bones). Most marsupials have a pouch for bearing young, but not all have it equally developed; there are species that do not have a pouch.

Marsupials are different special structure lower jaw, the lower (posterior) ends of which are curved inward. Their coracoid bone is fused with the scapula. The teeth of marsupials are represented by incisors (divided into polyincisal and biincisal) and molars, which have blunted tubercles; there are no fangs or they are underdeveloped. The mammary glands of animals have nipples to which newly born babies are attached. The mammary ducts open at the edge of the nipples, as in monkeys and humans, and not into the internal reservoir, as in most mammals. The underdeveloped baby that is born is attached to the nipple in the pouch, and its further development takes place there. The size of a newborn large gray kangaroo does not exceed 25 mm, in others it is even smaller (up to 7 mm). Milk is injected into the baby's mouth by contraction of special muscles of the mammary glands. The baby, despite its underdevelopment, is so firmly attached to the nipple that it is difficult to separate it. Usually the number of nipples corresponds to the number of cubs.

Different types of marsupials spend different periods of time in the pouch until the moment when the baby is able to feed on food other than milk. The mother usually looks for a nest or den in advance, where the children live for some time under her supervision. Marsupials live in various places: forests, steppes, mountains; They can run, climb, live in burrows and underground. Among marsupials, various species of kangaroos are well known, moving by jumping on highly developed hind limbs; shortened forelimbs are used to capture food. The predatory marsupial wolf, almost completely exterminated, resembles appearance dog.

Marsupial bear The leaf-eating koala lives on eucalyptus trees. Eat marsupial martens, marsupial squirrels and marsupial flying squirrels leading wood image life. Blind marsupial moles live in the soil. The most primitive of marsupials - opossums - inhabit the American continent. Opossums are almost omnivores. Possum fur is used to make outerwear, the meat is edible. In general, many marsupials provide valuable furs, and kangaroo meat good quality. In the Paleogene they were widespread, but later (except for Australia and America) they were replaced by highly organized mammals.