What features make the platypus similar to birds? Subclass of the First Beast (Prototheria). Platypuses in history
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Subclass of the First Beast (Prototheria)
Order Monotremes, or Oviparous (Monotremata) (E. V. Rogachev)
Monotremes (or oviparous) are the most primitive among modern mammals, retaining a number of archaic structural features inherited from reptiles (laying eggs, the presence of a well-developed coracoid bone not connected to the scapula, some details of the articulation of the skull bones, etc.). The development of their so-called marsupial bones (small pelvic bones) is also considered as a heritage of reptiles.
The presence of distinct coracoid bones distinguishes monotremes from marsupials and other mammals, in which this bone has become a simple outgrowth of the scapula. At the same time, hair and mammary glands are two interrelated characteristics characteristic of mammals. However, the mammary glands of oviparous animals are primitive and similar in structure to the sweat glands, while the mammary glands of marsupials and higher mammals are grape-shaped and similar to the sebaceous glands.
Quite a few similarities between monotremes and birds are adaptive rather than genetic. The laying of eggs by these animals brings monotremes closer to reptiles than to birds. However, in the egg, the yolk of monotremes is much less developed than that of birds. The keratinized egg shell is composed of keratin and also resembles the shell of reptile eggs. Birds are also reminiscent of such structural features as some reduction of the right ovary, the presence of pockets in the digestive tract resembling a bird's crop, and the absence of an external ear. However, these similarities are rather adaptive in nature and do not give the right to talk about any direct relationship between monotremes and birds.
Adult oviparous animals have no teeth. In 1888, milk teeth were discovered in a baby platypus, which disappear in an adult animal; these teeth are varied in structure, like those of higher mammals, and the two largest teeth on each jaw have the location and appearance of molars. In terms of body temperature, monotremes occupy an intermediate position between poikilotherms (reptiles) and true warm-blooded animals (mammals and birds). The body temperature of the echidna fluctuates around 30°, and that of the platypus - about 25°. But these are only average numbers: they change depending on the external temperature. Thus, the body temperature of an echidna increases by 4-6° when the environmental temperature changes from +5° to +30° C.
Currently, the order of monotremes has 5 living representatives belonging to two families: the platypus and 4 species of echidnas. All of them are distributed only in Australia, New Guinea and Tasmania (Map 1).
Family Platypuses (Ornithorhynchidae)
The only representative of the family is platypus(Ornithorhynchus anatinus) - was discovered at the very end of the 18th century. during the colonization period of New South Wales. In a list of animals of this colony published in 1802, the platypus was first mentioned as “an amphibian animal of the genus of moles... Its most curious quality is that it has a duck’s beak instead of an ordinary mouth, allowing it to feed in the mud like birds. ..". It was also noted that this animal digs a hole for itself with its claws. In 1799 Shaw and Nodder gave it a zoological name. European colonists called it "platypus", "duck mole", "water mole". Currently, Australians call it "platypus" (Fig. 14).
The very first scientific description of the platypus marked the beginning of fierce debate. It seemed paradoxical that a furry mammal could have a duck's beak and webbed feet. The first platypus skins brought to Europe were considered a fake, the product of skilled eastern taxidermists who deceived gullible European sailors. When this suspicion dissipated, the question arose as to which group of animals to classify him in. The "secrets" of the platypus continued to be revealed: in 1824, Meckel discovered that the platypus has glands that secrete milk. It was suspected that this animal laid eggs, but this was proven only in 1884.
The platypus is a brown-furred animal, about 65 cm long, including the length of its flattened tail, similar to that of a beaver. The head ends in the famous "duck beak", which is actually just an extended beak-shaped snout covered with a special kind of skin rich in nerves. This “beak” of the platypus is a tactile organ that also serves for obtaining food.
The platypus's head is round and smooth, and there is no external ear. The front feet are heavily webbed, but the membrane, which serves the animal when swimming, folds when the platypus walks on land or if it needs claws for digging holes. The membranes on the hind legs are much less developed. The front legs play the main role in digging and swimming; the hind legs are of great importance when moving on land.
The platypus usually spends about two hours a day in water. He feeds twice: early in the morning and in the evening twilight. He spends most of his time in his hole, on land.
The platypus feeds on small aquatic animals. It stirs up the silt at the bottom of the reservoir with its beak and catches insects, crustaceans, worms and mollusks. Underwater he feels free, if, of course, there is an opportunity to catch his breath on the surface from time to time. Diving and rummaging in the mud, he is guided mainly by touch; His ears and eyes are protected by fur. On land, the platypus, in addition to touch, is guided by sight and hearing (Fig. 15).
Platypus burrows are located outside the water, including the entrance, located somewhere under the overhanging shore at a height of 1.2-3.6 m above water level. Only an exceptionally high flood can flood the entrance to such a hole. An ordinary hole is a semicircular cave dug under the roots of trees, with two or more entrances.
Every year, the platypus enters a short winter hibernation, after which it begins the breeding season. Males and females meet in the water. The male grabs the female's tail with his beak, and both animals swim in a circle for some time, after which mating occurs.
When the time comes for the female to lay eggs, she digs a special hole. First, he digs a gallery in the slope of the bank with a length of 4.5 to 6 m, at a depth of approximately 40 cm below the soil surface. At the end of this gallery, the female digs out the nesting chamber. In the water, the female searches for material for the nest, which she then brings into the hole with the help of her tenacious tail. She builds a nest from aquatic plants, willow twigs or eucalyptus leaves. The expectant mother carefully crushes the material that is too hard. Then she clogs the entrance to the corridor with one or more earthen plugs, each 15-20 cm; It makes plugs with the help of its tail, which it uses like a mason's spatula. Traces of this work can always be seen on the tail of female platypus, which in its upper part is shabby and hairless. Thus, the female seals herself in a dark shelter inaccessible to predators. Even a person could not reveal the secret of her nesting shelter for a long time. Having completed this painstaking and complex work, the female lays eggs.
The first time a platypus laid eggs was observed in 1884 by Caldwell in Queensland. She was then traced to Healesville Game Reserve in Victoria. These eggs are small (less than 2 cm in diameter), round, surrounded by a dirty white shell, consisting not of lime, like in birds, but of a soft, elastic horn-like substance, so that they can easily become deformed. Usually there are two eggs in a nest, sometimes one, three or even four.
The duration of incubation may vary. The famous expert on Australian animals, David Flay, found that incubation in the platypus does not exceed 10 days, and can last only a week, provided that the mother is in the nest. During incubation, the female lies, bending in a special way, and holds the eggs on her body.
The mammary glands of the platypus, discovered by Meckel in 1824, do not have a nipple and open outward with simple enlarged pores. From them, milk flows down the mother's fur, and the cubs lick it off. They grow quickly. During their feeding, the mother also feeds heavily; There is a known case where a nursing female ate earthworms and crustaceans overnight in quantities almost equal to her own weight.
The cubs are blind for 11 weeks, then their eyes open, but they continue to remain in the hole for another 6 weeks. These young, which feed only on milk, have teeth; As the animal grows, the milk teeth disappear and are replaced by simple horny plates. Only after 4 months do young platypuses go out on their first short excursion into the water, where they begin to clumsily search for food. The transition from dairy nutrition to adult nutrition is gradual. Platypuses are well tamed and live up to 10 years of age in captivity.
Platypuses are found in Queensland, New South Wales, Victoria, parts of South Australia and Tasmania. They are currently most abundant in Tasmania (Map 1).
The platypus is little picky about the composition of the water in which it searches for food. It tolerates both the cold and clear waters of the mountain streams of Australia's Blue Mountains and the warm and turbid waters of the rivers and lakes of Queensland.
Quaternary remains of the platypus have been found in southern Queensland. Fossil platypuses resembled modern ones, but were smaller in size.
Before human migration to Australia, the platypus' enemies were few in number. Occasionally he was attacked only monitor lizard(Varanus varius), python(Python variegatus) and a seal swimming into the river leopard seal. The rabbits brought by the colonists created a dangerous situation for him. By digging holes, rabbits disturbed the platypus everywhere, and in many areas it disappeared, losing territory to them. European settlers also began to hunt the platypus for its skin. Many animals fell into traps set along the banks of rivers for rabbits, and into fishermen’s boats.
Wherever people destroyed or disturbed the platypus, the surviving animals left these places. Where a person did not bother him, the platypus tolerated his proximity well. To ensure the existence of the platypus, the Australians created a system of nature reserves and “refuges”, among which the most famous are Healesville Nature Reserve in Victoria and West Burleigh Nature Reserve in Queensland.
The platypus is an easily excitable, nervous animal. According to D. Fley, the sound of a voice or footsteps, some unusual noise or vibration, is enough for the platypus to be out of balance for many days, or even weeks. Therefore, for a long time it was not possible to transport platypuses to zoos in other countries. In 1922, the first platypus ever seen in other countries arrived at the New York Zoo; here he lived only 49 days; Every day for an hour it was shown to the public. Transportation became possible thanks to G. Burrell, who invented an artificial dwelling for the platypus, consisting of a reservoir of water (reservoir), a sloping labyrinth imitating a hole with rubber “soil,” and a supply of worms to feed the animal. To show the animal to the public, the wire cover of the living chamber of the platypus burrow was dislodged.
Platypuses were brought to the same zoo in New York twice: in 1947 and 1958. These transportations were organized by D. Flay. In 1947, three platypuses were transported to New York by sea; one of them died after 6 months, and the other two lived in the zoo for 10 years. In 1958, three more platypuses were flown to New York.
Echidna family (Tachyglossidae)
The second family of the monotreme order includes echidnas, covered with quills, like porcupines, but reminiscent of anteaters in their feeding type. The size of these animals usually does not exceed 40 cm. The body is covered with needles, the length of which can reach 6 cm. The color of the needles varies from white to black. Under the needles the body is covered with short brown hair. The echidna has a thin, pointed snout 5 cm, ending in a narrow mouth. Longer tufts of hair are usually developed around the ears. The tail is almost not pronounced, there is only something like a protrusion at the back, covered with spines (Table 2).
Currently, there are 2 genera of echidnas: the echidna itself(genus Tachyglossus), living in Australia, and New Guinea echidnas(genus Proechidna). In the genus Tachyglossus there are 2 species: Australian echidna(T. aculeatus), one of the subspecies of which is endemic to New Guinea, and Tasmanian echidna(T. se~ tosus), distinguished by its larger size and thick hair, from which sparse and short needles protrude. The difference in the fur of these animals is likely due to the colder and wetter climate of Tasmania.
The echidna is found in Australia, in the eastern half of the continent and on its western tip, in Tasmania and New Guinea. The Tasmanian echidna is found in Tasmania and several islands in the Bass Strait.
The discovery of the echidna early in the colonization of New South Wales did not immediately receive the attention it deserved. In 1792, Shaw and Nodder described the Australian echidna and named it Echidna aculeata. In the same year, a Tasmanian species was discovered, described by Geoffroy as Echidna setosa. The echidna is a purely terrestrial animal. It lives in dry bush (brush thickets), preferring rocky areas. She doesn't dig holes. Its main defense is needles. When disturbed, the echidna curls up into a ball, like a hedgehog. With the help of its claws, it can partially burrow into loose soil; burying the front part of the body, she exposes the enemy only to needles directed backwards. During the day, hiding in the voids under roots, stones or in hollows, the echidna rests. At night she goes in search of insects. In cold weather, she remains in her den, falling into a short hibernation, like our hedgehogs. Subcutaneous fat reserves allow her to fast for a month or more if necessary.
The echidna's brain is more developed than that of the platypus. She has very fine hearing, but poor eyesight: she sees only the closest objects. During its excursions, mostly at night, this animal is guided mainly by its sense of smell.
The echidna feeds on ants, termites and other insects, and sometimes other small animals (earthworms, etc.). She destroys anthills, moves stones, pushing them with her paws, even quite heavy ones, under which worms and insects hide.
The strength of the echidna's muscles is amazing for an animal of such small size. There is a story about a zoologist who locked an echidna in the kitchen of his house for the night. The next morning he was very surprised to see that the echidna had moved all the furniture in the kitchen.
Having found an insect, the echidna throws out its thin, long and sticky tongue, to which the prey sticks.
The echidna has no teeth at all stages of its development, but on the back of its tongue there are horny denticles that rub against the comb palate and grind caught insects. With the help of its tongue, the echidna swallows not only insects, but also earth and particles of rocky detritus, which, entering the stomach, complete the grinding of food, similar to how it happens in the stomach of birds.
Like the platypus, the echidna incubates its eggs and feeds its young with milk. A single egg is placed in a primitive pouch, which is formed by the breeding season (Fig. 16). How the egg gets into the bag is still unknown exactly. G. Burrell proved that the echidna cannot do this with the help of its paws, and put forward another hypothesis: its body is flexible enough so that, by bending, the female can lay an egg directly into the abdominal pouch. One way or another, the egg is “hatched” in this pouch, where it hatches into a baby. To get out of the egg, the baby breaks the shell using a horny bump on its nose.
Then he sticks his head into the hairy sac where the mammary glands open, and licks the milky secretions from the hairs of this sac. The baby stays in the pouch for quite a long time until its quills begin to develop. Then the mother leaves him in some shelter, but for some time she visits him and feeds him milk.
The echidna tolerates captivity well if it has protection from excess sun, from which it suffers greatly. She happily drinks milk, eats eggs and other food that can fit in her narrow, tube-like mouth. Her favorite treat is raw eggs, the shells of which have a hole punched into them where the echidna can stick her tongue. Some echidnas lived up to 27 years in captivity.
Aborigines, who loved to feast on echidna fat, often hunted it, and in Queensland they even specially trained dingoes to hunt echidnas.
Prochidna(genus Proechidna) are found in New Guinea. They differ from Australian echidnas by a longer and curved snout (“beak”) and high three-fingered limbs, as well as small external ears (Fig. 17). Two now extinct species of echidna are known from the Quaternary, but this group is unknown from older deposits. The origin of echidnas is as mysterious as the origin of the platypus.
1. Is the statement true: “Caring for offspring leads to a reduction in the birth rate in animals”? Prove your point
Yes, that's right. Bearing cubs, viviparity, feeding with milk, caring for offspring ensure better safety of the young in a diverse environment
2. Name the smallest and largest representative of the class Mammals
Pygmy shrew - 4 cm
Blue whale - up to 33 cm
3. List the specific features of mammals
Two pairs of five-fingered limbs; cervical spine - of 7 vertebrae; teeth differ in structure and functions; there are mammary, sweat, glands; the body is covered with wool; four-chambered heart; the cerebral cortex and sensory organs are developed; four-chambered heart
4. It is known that crocodiles have teeth of different sizes. But it is the teeth of mammals that are called specialized. Explain why
In crocodiles, the teeth differ only in size, but in mammals they differ not only in size, but also in the functions they perform: there are incisors, fangs, molars
Order Monotremes
1. What signs bring oviparous animals closer to reptiles?
Body temperature is not constant. They reproduce by laying eggs. The eggs are covered with a keratinized shell, reminiscent of a reptile's shell.
2. Read the text. What animal is described here?
Lives in Australia. Its body is covered with needles, its beak is tubular. Body temperature is variable - up to 30°C. It reproduces by eggs, which it incubates in a leathery pouch on its belly. Uses sharp claws to dig holes
Answer: echidna
3. Why are primal animals subject to protection?
Prime beasts are very rare animals
Order Marsupials
1. What feature of the life cycle of this group of mammals is reflected in the name of this order?
Marsupials have a special fold of skin on their belly in the form of a pocket where newborns are placed
2. Fill out the table by selecting from the proposed habitat options and food rations for marsupial mammals indicated in the table
Habitat:
1. lives in trees
2. lives on eucalyptus trees
3. lives in the soil, digs holes
4. lives near streams and rivers
A. feeds on small fish and aquatic invertebrates
B. feeds on insects, larvae, worms
V. feeds on eucalyptus leaves
G. feeds on birds and rodents
D. eats plant and animal foods
Order Insectivores
1. Name the representatives of the order Insectivores, for which the name of the order only partially reflects their nutritional diet
Shrew, mole, muskrat
2. Name the smallest and largest representative of the squad
Shrew crumb - up to 4 cm
Common desman - up to 22 cm
3. Guess what significance an elongated muzzle and proboscis have for this group of animals
With their help, insectivores catch insects from their burrows and passages.
4. Look at the figure. 129 of the textbook (p. 161). Name which of the insectivores shown in the picture lives in the soil
Order Chiroptera
1. What is common in the method of movement of birds and bats?
Birds and bats are capable of long flapping flight
2. Name two suborders of bats
1. Fruit bats
2. Bats
3. What method of orientation allows bats to actively lead a nocturnal lifestyle?
Bats are capable of echolocation. In flight, they produce high-frequency sounds (ultrasounds). Sound waves reflected from obstacles are captured by the large ears of bats. The nature of the reflected sound of the mouse determines the distance to the object
4. Why do we rarely see bats in nature, although they are quite widespread?
Bats are active at night
5. What is the significance of the decrease in body temperature of bats during sleep?
Their metabolism decreases and their energy expenditure slows down.
6. Look at the pictures. Label under each picture the name of the order and species to which the animal belongs.
Order Chiroptera. View of the Red-haired noctule
Order Insectivores. Muskrat species
Order Monotremes. Platypus species
Order Marsupials. Species Marsupial wolf
Order Insectivores. Species Mole
The platypus is an amazing animal that lives only in Australia, on the island of Tasmania. This strange miracle belongs to mammals, but, unlike other animals, it lays eggs like an ordinary bird. Platypuses are oviparous mammals, a rare species of animal that survives only on the Australian continent.
History of discovery
Strange creatures boast an unusual history of their discovery. The first description of the platypus was given by Australian pioneers in the early 18th century. For a long time, science did not recognize the existence of platypuses and considered the mention of them to be an inept joke by Australian residents. Finally, at the end of the 18th century, scientists at a British university received a parcel from Australia containing the fur of an unknown animal, similar to a beaver, with paws like an otter, and a nose like an ordinary domestic duck. Such a beak looked so ridiculous that scientists even shaved the hair on the face, believing that Australian jokers had sewn a duck nose to the skin of a beaver. Finding no seams or traces of glue, the pundits simply shrugged their shoulders. No one could understand where the platypus lived or how it reproduced. Only a few years later, in 1799, the British naturalist J. Shaw proved the existence of this miracle and gave the first detailed description of the creature, which was later given the name “platypus.” Photos of the bird beast can only be taken in Australia, because this is the only continent on which these exotic animals currently live.
Origin
The appearance of platypuses dates back to those distant times when modern continents did not exist. All land was united into one huge continent - Gondwana. It was then, 110 million years ago, that platypuses appeared in terrestrial ecosystems, taking the place of recently extinct dinosaurs. Migrating, platypuses settled throughout the continent, and after the collapse of Gondwana, they remained to live on a large area of the ex-continent, which was later named Australia. Due to the isolated location of their homeland, the animals have retained their original appearance even after millions of years. Various species of platypuses once inhabited the vast expanses of the entire land, but only one species of these animals has survived to this day.
Classification
For a quarter of a century, the leading minds of Europe puzzled over how to classify the overseas beast. Particularly difficult was the fact that the creature had a lot of characteristics that are found in birds, animals, and amphibians.
The platypus stores all its fat reserves in the tail, and not under the fur on the body. Therefore, the tail of the animal is solid, heavy, and is capable of not only stabilizing the movement of the platypus in the water, but also serves as an excellent means of defense. The weight of the animal fluctuates around one and a half to two kilograms with a length of half a meter. Compare with a domestic cat, which, with the same dimensions, weighs much more. Animals do not have nipples, although they produce milk. The temperature of the bird beast is low, barely reaching 32 degrees Celsius. This is much lower than that of mammals. Among other things, platypuses have one more literally amazing feature. These animals can infect with poison, which makes them quite dangerous opponents. Like almost all reptiles, the platypus lays eggs. What makes platypuses similar to snakes and lizards is their ability to produce poison and the arrangement of their limbs, like those of amphibians. The gait of the platypus is amazing. It moves by bending its body like a reptile. After all, its paws do not grow from below the body, like those of birds or animals. The limbs of this either a bird or an animal are located on the sides of the body, like those of lizards, crocodiles or monitor lizards. High on the animal's head are the eyes and ear openings. They can be found in depressions located on each side of the head. There are no auricles; when diving, it covers its eyes and ears with a special fold of skin.
Mating games
Every year, platypuses hibernate, which lasts 5-10 short winter days. After this comes the mating period. Scientists have recently discovered how the platypus reproduces. It turns out, like all the main events in the life of these animals, the courtship process takes place in water. The male bites the tail of the female he likes, after which the animals circle each other in the water for some time. They do not have permanent pairs; platypus children remain only with the female, who herself raises and raises them.
Waiting for the Cubs
A month after mating, the platypus digs a long, deep hole, filling it with armfuls of wet leaves and brushwood. The female carries everything she needs, wrapping her paws around her and tucking her flat tail under. When the shelter is ready, the expectant mother lies down in the nest and covers the entrance to the hole with earth. The platypus lays its eggs in this nesting chamber. The clutch usually contains two, rarely three, small whitish eggs, which are glued together with a sticky substance. The female incubates the eggs for 10-14 days. The animal spends this time curled up in a ball on the masonry, hidden by wet leaves. At the same time, the female platypus can occasionally leave the hole in order to have a snack, clean itself and wet its fur.
Birth of platypuses
After two weeks of residence, a small platypus appears in the clutch. The baby breaks the eggs with an egg tooth. Once the baby emerges from the shell, this tooth falls off. After birth, the female platypus moves the young onto her abdomen. The platypus is a mammal, so the female feeds its young with milk. Platypuses do not have nipples; milk from the enlarged pores on the mother’s belly flows down the fur into special grooves, from where the young lick it off. The mother occasionally goes outside to hunt and clean herself, while the entrance to the hole is blocked with earth.
Up to eight weeks, the cubs need the warmth of their mother and can freeze if left unattended for a long time.
At the eleventh week, the eyes of small platypuses open; after four months, the babies grow up to 33 cm in length, grow hair and completely switch to adult food. A little later they leave the hole and begin to lead an adult lifestyle. At the age of one year, the platypus becomes a sexually mature adult.
Platypuses in history
Before the first European settlers appeared on the shores of Australia, platypuses had virtually no external enemies. But their amazing and valuable fur made them an object of hunting for white people. The skins of platypuses, black-brown on the outside and gray on the inside, were at one time used to make fur coats and hats for European fashionistas. And the local residents did not hesitate to shoot the platypus for their own needs. At the beginning of the twentieth century, the decline in the number of these animals acquired alarming proportions. Naturalists sounded the alarm, and the platypus joined the ranks. Australia began to create special reserves for amazing animals. The animals were taken under state protection. The problem was complicated by the fact that the places where the platypus lives must be protected from human presence, since this animal is shy and sensitive. In addition, the massive spread of rabbits on this continent deprived platypuses of their usual nesting places - their holes were occupied by long-eared aliens. Therefore, the government had to allocate huge areas, fenced off from outside interference, in order to preserve and increase the platypus population. Such reserves played a decisive role in preserving the numbers of these animals.
Platypuses in captivity
Attempts have been made to introduce this animal into zoos. In 1922, the first platypus arrived at the New York Zoo and lived in captivity for only 49 days. Due to their desire for silence and increased timidity, the animals never mastered zoos; in captivity, the platypus lays eggs reluctantly, and only a few offspring were obtained. There are no recorded cases of human domestication of these exotic animals. Platypuses were and remain wild and distinctive Australian aborigines.
Platypuses today
Now platypuses are not considered. Tourists enjoy visiting places where the platypus lives. Travelers willingly publish photos of this animal in their stories about Australian tours. Images of poultry animals serve as a distinctive feature of many Australian products and manufacturing companies. Along with the kangaroo, the platypus has become a symbol of the Australian continent.
Monotremes (or oviparous) are the most primitive among modern mammals, retaining a number of archaic structural features inherited from reptiles (laying eggs, the presence of a well-developed coracoid bone not connected to the scapula, some details of the articulation of the skull bones, etc.) - Their development is like this The so-called marsupial bones (small pelvic bones) are also considered as a heritage of reptiles.
The presence of distinct coracoid bones distinguishes monotremes from marsupials and other mammals, in which this bone has become a simple outgrowth of the scapula. At the same time, hair and mammary glands are two interrelated characteristics characteristic of mammals. However, the mammary glands of oviparous animals are primitive and similar in structure to the sweat glands, while the mammary glands of marsupials and higher mammals are grape-shaped and similar to the sebaceous glands.
Quite a few similarities between monotremes and birds are adaptive rather than genetic. The laying of eggs by these animals brings monotremes closer to reptiles than to birds. However, in the egg, the yolk of monotremes is much less developed than that of birds. The keratinized egg shell is composed of keratin and also resembles the shell of reptile eggs. Birds are also reminiscent of such structural features as some reduction of the right ovary, the presence of pockets in the digestive tract resembling a bird's crop, and the absence of an external ear. However, these similarities are rather adaptive in nature and do not give the right to talk about any direct relationship between monotremes and birds.
In terms of body temperature, monotremes occupy an intermediate position between poikilotherms (reptiles) and true warm-blooded animals (mammals and birds). The body temperature of the echidna fluctuates around 30°, and that of the platypus - about 25°. But these are only average numbers: they change depending on the external temperature. Thus, the body temperature of an echidna increases by 4-6° when the environmental temperature changes from +5° to +30° C.
Interestingly, the appearance of the first dinosaurs and other archosaurs, at one time, was marked by the massive (but not complete) extinction of therapsids, the highest forms of which were very close in organization to monotreme mammals, and, according to some assumptions, may have had mammary glands and wool. Currently, the order of monotremes has 2 families: echidnas and platypuses; 3 types.
2 families: platypus and echidnaidae
Range: Australia, Tasmania, New Guinea
Food: insects, small aquatic animals
Body length: from 30 to 80 cm
Subclass oviparous mammals represented by only one order - monotremes. This order unites only two families: platypuses and echidnas. Monotremes- the most primitive living mammals. They are the only mammals that, like birds or reptiles, reproduce by laying eggs. Oviparous animals feed their young with milk and are therefore classified as mammals. Female echidnas and platypuses do not have nipples, and the young lick milk secreted by tubular mammary glands directly from the fur on the mother's belly.
Amazing animals
Echidnas and platypuses- the most unusual representatives of the class of mammals. They are called monotremes because both the intestines and the bladder of these animals open into one special cavity - the cloaca. Two oviducts in monotreme females also exit there. Most mammals do not have a cloaca; this cavity is characteristic of reptiles. The stomach of oviparous animals is also amazing - like a bird's crop, it does not digest food, but only stores it. Digestion occurs in the intestines. These strange mammals even have a lower body temperature than others: without rising above 36°C, it can drop to 25°C depending on the environment, like in reptiles. Echidnas and platypuses are voiceless - they have no vocal cords, and only young platypuses have toothless - quickly decaying teeth.
Echidnas live up to 30 years, platypuses - up to 10. They live in forests, steppes overgrown with bushes, and even in the mountains at an altitude of up to 2500 m.
Origin and discovery of oviparous
Short fact
Platypuses and echidnas are venom-bearing mammals. They have a bone spur on their hind legs, along which poisonous liquid flows. This poison causes rapid death in most animals, and severe pain and swelling in humans. Among mammals, besides the platypus and echidna, only representatives of the order of insectivores are poisonous - the slittooth and two species of shrews.
Like all mammals, oviparous animals trace their origins to reptile-like ancestors. However, they separated from other mammals quite early, choosing their own path of development and forming a separate branch in the evolution of animals. Thus, oviparous animals were not the ancestors of other mammals - they developed in parallel with them and independently of them. Platypuses are more ancient animals than echidnas, which descended from them, modified and adapted to a terrestrial lifestyle.
Europeans learned about the existence of oviparous animals almost 100 years after the discovery of Australia, at the end of the 17th century. When the skin of a platypus was brought to the English zoologist George Shaw, he decided that he was simply being played, the sight of this bizarre creature of nature was so unusual for Europeans. And the fact that the echidna and platypus reproduce by laying eggs has become one of the greatest zoological sensations.
Despite the fact that the echidna and platypus have been known to science for quite some time, these amazing animals still present zoologists with new discoveries.
Wonder Beast platypus as if assembled from parts of different animals: its nose is like a duck’s beak, its flat tail looks like it was taken from a beaver with a shovel, its webbed feet look like flippers, but are equipped with powerful claws for digging (when digging, the membrane bends, and when walking, it folds, without interfering with free movement). But despite all the seeming absurdity, this animal is perfectly adapted to the lifestyle that it leads, and has hardly changed over millions of years.
The platypus hunts small crustaceans, mollusks and other small aquatic life at night. Its tail-fin and webbed paws help it dive and swim well. The eyes, ears and nostrils of the platypus close tightly in the water, and it finds its prey in the dark underwater with the help of its sensitive “beak”. This leathery “beak” contains electroreceptors that can detect weak electrical impulses emitted by aquatic invertebrates as they move. Reacting to these signals, the platypus quickly finds prey, fills its cheek pouches, and then leisurely eats what it has caught on the shore.
The platypus sleeps all day near a pond in a hole dug with powerful claws. The platypus has about a dozen of these holes, and each has several exits and entrances - not an extra precaution. To breed offspring, the female platypus prepares a special hole lined with soft leaves and grass - it is warm and humid there.
Pregnancy lasts a month, and the female lays one to three leathery eggs. The mother platypus incubates the eggs for 10 days, warming them with her body. Newborn tiny platypuses, 2.5 cm long, live on their mother’s belly for another 4 months, feeding on milk. The female spends most of her time lying on her back and only occasionally leaves the hole to feed. When leaving, the platypus seals the cubs in the nest so that no one will disturb them until she returns. At 5 months of age, mature platypuses become independent and leave the mother's hole.
Platypuses were mercilessly exterminated for their valuable fur, but now, fortunately, they are taken under the strictest protection, and their numbers have increased again.
A relative of the platypus, it doesn’t look like it at all. She, like the platypus, is an excellent swimmer, but she does it only for pleasure: she does not know how to dive and get food under water.
Another important difference: the echidna has brood pouch- a pocket on the belly where she places the egg. Although the female raises her cubs in a comfortable hole, she can safely leave it - the egg or newborn cub in her pocket is reliably protected from the vicissitudes of fate. At the age of 50 days, the little echidna already leaves the pouch, but for about 5 more months it lives in a hole under the auspices of a caring mother.
The echidna lives on the ground and feeds on insects, mainly ants and termites. Raking termite mounds with strong paws with hard claws, she extracts insects with a long and sticky tongue. The echidna's body is protected by spines, and in case of danger it curls up into a ball, like an ordinary hedgehog, exposing its prickly back to the enemy.
wedding ceremony
From May to September, the echidna's mating season begins. At this time, the female echidna receives special attention from the males. They line up and follow her in single file. The procession is led by the female, and the grooms follow her in order of seniority - the youngest and most inexperienced close the chain. So, in company, echidnas spend a whole month, looking for food together, traveling and relaxing.
But the rivals cannot coexist peacefully for long. Demonstrating their strength and passion, they begin to dance around the chosen one, raking the earth with their claws. The female finds herself in the center of a circle formed by a deep furrow, and the males begin to fight, pushing each other out of the ring-shaped hole. The winner of the tournament receives the favor of the female.