Siren family

This family of tailed amphibians contains animals of the simplest organization. In them, just like in the previous family, the gills are preserved throughout life, the maxillary bones and eyelids also do not exist, but the premaxillary bones and lower jaw have no teeth at all, so the mouth is completely toothless and the jaws are covered with horny plates; small teeth are preserved only on the vomer. There are only two known genera of sirens that live in North America and differ from each other in the number of gill slits, as well as in the number of fingers on the forelimbs *; There are no hind limbs at all.

* The number of species in the family has now increased to 3.

Only one species is known in each genus. According to Cope, sirens are not only animals with an underdeveloped skeleton, as can be seen in the structure of the skull, shoulder girdle, pelvis and limbs, but they also exhibit a retrograde transformation in the development of the gills. This naturalist found that in youth the gills of sirens do not function at all and they develop gradually only with age. Cope concludes from this that the sirens were formed from animals similar to land salamanders and only subsequently adapted to life in water *.

* The siren's gills actually undergo the most curious transformations. In newly hatched larvae, they grow very large; with further body growth, their size decreases, and then increases again. This phenomenon is called "Cop's reverse metamorphosis."

Big siren(Siren laeertina) is similar in body structure to the eel amphium and differs from it in that it has only one front pair of limbs. The body is elongated and valval, pointed at the back and compressed at the sides, there are four fingers on the forelimbs, and traces of the hind limbs are not visible even on the skeleton. The nostrils are located near the edge of the upper lip, small round eyes are covered with skin. The gill slits look like three inclined cuts on each side of the neck; external gills are attached to their upper ends. The vomers have two large rows of teeth that form an angle with each other. There are 101-108 vertebrae and their structure is similar to the vertebrae of Proteus, 8 of them, starting from the second, have small costal appendages. The color of the body is blackish and the same both above and below, but somewhat lighter below; in some places small white spots are noticeable. The animal is 67-72 cm long. Siren lives in the southeastern part of the United States and reaches as far west as southwest Texas.
Garden introduced us to these animals in 1766; he found sirens in South Carolina and sent two copies to Ellis in London, and told him that sirens were found in swamps, mainly under tree trunks lying in the water**; sometimes they crawl out onto these trunks, and when the water dries up, they squeak pitifully, almost like young ducks, only louder and clearer.

* * In reservoirs, this species usually chooses shallow, shaded places, sometimes even “drilling” into the ground. And the dwarf siren (Siren intermedia) even forms a “cocoon” in the ground during periods of drought, from which only its mouth is visible.

Garden mistook this animal for a fish, but this opinion was refuted by Linnaeus. Dallas later considered it to be a tadpole of some salamander, and Cuvier for the first time expressed the opinion that the siren should be considered a fully developed animal.
In June 1825, a live siren, 1/2 meter long, was sent to England and lived there for six years under the supervision of Neil, who closely observed him. At first, this naturalist kept the siren in a barrel of water, at the bottom of which lay sand; this barrel was placed inclined so that the animal could go out onto land, but it soon turned out that it was more convenient to put moss, but since it was constantly rotting and had to be changed often, they put frogweed (Hydrocharis morsits ranae) in the water, under the floating leaves of which the sirens loved to hide. In the summer he ate earthworms, small sticklebacks, newt tadpoles, and later also minnows (Phoxinus laevis), but in the winter he fasted from mid-October to the end of April, living in a cold greenhouse. If you touched his tail, he blew bubbles and quietly swam away.
On May 13, 1826, after eating a hearty meal, he himself climbed out of the barrel and fell to the floor from a height of one meter. The next day he was found outside the greenhouse on the path; he dug himself a meter-long passage under the wall and escaped through it. Due to the cold morning, he was completely numb and barely showed signs of life; planted in the water, he breathed difficultly and rose to the surface of the water to take in air; However, after a few hours, Siren completely recovered.

When he was moved to a greenhouse in 1827, he became more lively and began to croak like a frog. During this summer he often ate 2 small earthworms at a time and was generally hungrier than before. As soon as he noticed a worm, he carefully approached, stopped for a moment, as if looking closely, and then quickly grabbed it. In general, he ate only once every 8 or 10 days. Usually he lay for several hours at the bottom of the water, not blowing bubbles; twice a minute a slight movement of water behind the gills was noticeable. When touched, he swam away so quickly that the water rose in splashes. This Siren lived until October 22, 1831 and died a violent death: he was found falling out of a barrel with dried gills. During these six years he grew 10 cm.

Animal life. - M.: State Publishing House of Geographical Literature. A. Brem. 1958.

See what “Siren Family” is in other dictionaries:

The family unites typical predators, for the most part average size, well adapted to actively catching animals, chasing them or hiding them. The body of all members of the family is elongated, resting on slender... Biological encyclopedia

They are unmistakably identified by numerous parallel stripes of folds on the belly. Sits in the back third or quarter of the body dorsal. The head is relatively flattened, with a low and wide oral cavity, which houses the filter... ... Biological encyclopedia

The small family of sirens includes 3 species belonging to 2 genera. Distributed in the southeastern part North America. These peculiar amphibians have only forelimbs with 4 or 3 fingers and external feathery gills in... ... Biological encyclopedia

Sirens, lilacs (Sirenidae), a family from the order of tailed amphibians. The body is long, valky. Hind legs are missing. External gills are retained throughout life. The eyes are small and lack lids. Instead of maxillary bones there are horny ones... ...

I with irena plural A family of tailed amphibians with a long, serpentine body that retains external gills throughout their lives. II sirens pl. An order of herbivorous aquatic mammals, representatives of which are now very rare... Modern explanatory dictionary Russian language Efremova

In the wild rocky mountains of Africa and western Asia, vibrant life is often noticeable: small animals the size of rabbits, basking in the sun on some rock ledge, frightened by the appearance of a person, quickly run along the steep... ... Animal life

I Sirens in ancient times Greek mythology half-birds, half-women. According to Homer's Odyssey, with their magical singing S. lured sailors to the coastal rocks on which ships crashed. Odysseus, in order to save his companions, covered their ears... Great Soviet Encyclopedia

In April 1860, as Praeger says, we were on Capuas, the most large river Kalimantan Islands. Here, during high tide, we heard quite clearly music, now louder, now quieter, now far away, now close. From... ...Animal life

- (Sirenia)* * Sirens special squad mammals, like whales, completely converted to water image life. Their closest terrestrial relatives are elephants and hyraxes. In the structure of the skull, sirens retained quite a lot of similarities with primitive ones... ... Animal life

Let's talk about almost mythical creatures, living today in sea ​​depths planet Earth. We will talk about mysterious animals belonging to Siren squad . The very name “siren” evokes an association among most people with mythological creatures ancient world- beautiful water maidens - half-fish, who with their magnificent appearance and singing lured sailors, and then mercilessly killed them. Who are sirens really, what do they look like, and do they exist in nature at all, you ask. Let's take a closer look Siren squad and its representatives.

Siren Squad: Habitat

Sirens really exist, but they are not at all beautiful maidens - half-humans, half-fish. This marine mammals who are fully adapted to life in sea ​​water. Sirens lat. Sirenia) is an order of marine herbivorous mammals that belong to the class Mammals, the infraclass Placentals and the superorder Afrotheria. These animals live exclusively in water (mostly sea water) and never go onto land.

Animals related to Siren squad , are quite large in size, but unlike cetaceans, they prefer to stay in shallow water, and sometimes enter freshwater rivers and lakes connected to them. They live in hot tropical and subtropical climate. Africa is considered the ancestral home of these animals; scientists consider hyraxes and proboscideans to be their closest relatives.

Amazonian manatees

Origin

Biologists suggest that the ancestors of animals belonging to Siren squad , are land-dwelling herbivorous mammals that lived in shallow water areas and lived during the Eocene period, according to numerous fossil remains found. The age of ancient artifacts - the fossilized remains of the ancestors of the sirens - is about 50 million years old. It is also assumed among scientists that in the process of evolution, the hind limbs of these aquatic mammals quickly disappeared, and instead of them a horizontal fin was formed.

Dugong and stickfish

It is believed that three families formed during the Eocene period Siren squad: Prorastomidae, Protosirenidae and Dugongidae (Dugongidae), and Trichechidae (Manatees) appeared later, only in the Miocene. So as you see, Siren squad a very ancient order of mammals, among all that currently exist on our planet. Two families Prorastomidae and Protosirenidae from the order in question are completely extinct and do not currently exist.

Classification

In the modern worldSiren squad represented by two families:

• the first family Dugongidae (lat. Dugongidae) consisting of a single species - dugong;

• the second family Manatees (lat. Trichechidae), consisting of four species:

— African manatee (lat. Trichechus senegalensis);

— American manatee (lat. Trichechus manatus);

— Amazonian manatee (lat. Trichechus inunguis);

— Dwarf manatee (lat. Trichechus bernhardi).

Manatees

Appearance

All animals related to squad Sirens They have a massive and very awkward cylindrical body. The forelimbs have changed greatly in the process of evolution and turned into fins, shaped like the fins of cetaceans. The hind limbs have completely disappeared. The tail of sirens also has the shape of a fin. The entire body of these ancient animals is covered with very thick, completely hairless skin, forming voluminous folds.

The muzzle is elongated and has a somewhat “chopped-off” appearance, with decorations in the form of stiff whiskers. It must be said that these mustaches serve the sirens not so much as decoration, but as the main organs of touch.

Interestingly, the volume of the lungs in these animals can be adjusted in each half independently of each other; this determines the change in the center of gravity, which the sirens can change at will and control the stability of their body.

The number of teeth in these aquatic mammals varies, and the palate and relatively short, thick tongue are covered with a calloused, somewhat keratinized layer, which probably facilitates the consumption of tough aquatic plants.

Manatees

Lifestyle

It should be noted that animals Siren squad are not herd animals. They either live alone or try to stay in small groups, only when they are in places with plenty of food. It is sometimes noted that after mating season these animals keep pairs for for many years, and it happens that they become devoted to each other until the end of their lives.

American manatees

The diet of these aquatic mammals consists exclusively of various aquatic plants, and small amount small crabs that are probably caught by chance. Like all other aquatic mammals, animals belonging to Siren squad , despite their clumsiness, they are very mobile and fast in the water, but they try to avoid great depths.

With this short story, perhaps, we will finish the article dedicated to the amazing aquatic mammals that make up Siren squad . In the future, we will continue to get acquainted with individual representatives of this detachment.

Manatees

And in conclusion, I bring to your attention interesting documentaries, telling about the life of mysterious animals belonging to Siren squad

Synonyms Families Area

Prehistoric range

Modern range

Characteristic

Sirens are massive animals with a cylindrical body. Their forelimbs turned into fins, and their hind limbs completely disappeared during evolution; their remains cannot be identified even in the skeleton. Sirens do not have a dorsal fin, like some species of whales. The tail has transformed into a flat rear fin. The skin is very thick and folded, there is no hair. The muzzle is elongated, but flattened rather than sharp. She is surrounded by hard and sensitive whiskers, with which sirens touch objects. The nostrils are located relatively high. The volume of the lungs is regulated independently of each other, which allows you to shift the center of gravity and increases stability. Compared to the body, the head is quite large, however, the volume of the brain in relation to the size of the body is one of the smallest among all mammals. The number and shape of teeth varies greatly among individual genera of sirens. Incisors are often found in a degenerate form, and canines are absent in all modern species. The front of the roof of the mouth is covered with calloused layers, which probably aids in eating. The short tongue is also calloused.

Sirens live alone or in small groups. They always move slowly and carefully. Their food is exclusively vegetarian in nature and consists of sea grass and algae. Since the molars are constantly being worn down by the sand that has settled on the algae they eat, the worn-down teeth are replaced by teeth growing deeper in the mouth. The lifespan of sirens is about twenty years.

Evolution

Sirens have common land ancestors with proboscis and hyraxes. The earliest known fossils of siren-like animals date from the early Eocene and are about 50 million years old. These animals were quadrupeds and herbivores, still capable of moving on land, but already living mainly in shallow water. Subsequently, the ancestors of the sirens were very successful and widespread animals, as evidenced by numerous fossilized remains. Quite quickly the hind limbs disappeared, and instead a horizontal caudal fin developed.

Families formed in the Eocene Prorastomidae († ), Protosirenidae(†) and dugongs ( Dugongidae). Manatees appeared, according to the prevailing opinion among zoologists, only in the Miocene. There were no traces left of the first two families already in the Oligocene; since then, the order of sirens has been divided into only two families. In the Miocene and Pliocene, sirens were much more numerous and diverse than today. It is likely that changes in climate that occurred during the Pleistocene significantly reduced the sirenian order.

Classification

Two modern families sirens are:

• Dugongidae, includes one single living species, the dugong. About 250 years ago there was another species - Steller's cow, which is now extinct.
• Manatees (Trichechidae) - contains four species:
  • African manatee ( Trichechus senegalensis)
  • Amazonian manatee ( Trichechus inunguis)
  • American manatee ( Trichechus manatus)
  • Pygmy manatee ( Trichechus bernhardi)

Sirens and people

The name sirens comes from the sirens of Greek mythology, as from a distance they can easily be confused with bathing people. However, the singing of the legendary sirens does not suit these animals in any way. Christopher Columbus was not the first person to see sirens, but he is known to have mentioned them in his diary in 1493.

All modern views sirens are considered to be under threat. The main danger for them is motor boats, which with their propellers seriously injure these shallow-water-loving animals. Another threat is human destruction. environment and penetration into their traditional habitats. Due to their metabolism, sirens need large quantities algae, and their presence is directly related to water quality, which is increasingly falling due to human influence.

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Notes

Links

• Squad in the World Register marine species (World Register of Marine Species) (English)
• Sirens - Extinct Animals Wiki - Wikia

Prototheria (Primordial beasts) Metatheria (Metatherium) Eutheria (Eutheria, or Placental)

Excerpt characterizing Sirens (mammals)

– Are you also waiting for the commander-in-chief? - the hussar lieutenant colonel spoke. “Govog”yat, it’s accessible to everyone, thank God. Otherwise, there’s trouble with the sausage makers! It’s not until recently that Yeg “molov” settled in the Germans. Now, maybe it will be possible to speak in Russian. Otherwise, who knows what they were doing. Everyone retreated, everyone retreated. Have you done the hike? – he asked.
“I had the pleasure,” answered Prince Andrei, “not only to participate in the retreat, but also to lose in this retreat everything that was dear, not to mention property and home... a father who died of grief. I am from Smolensk.
- Eh?.. Are you Prince Bolkonsky? It’s great to meet: Lieutenant Colonel Denisov, better known as Vaska,” said Denisov, shaking Prince Andrei’s hand and peering into Bolkonsky’s face with especially kind attention. “Yes, I heard,” he said with sympathy and, after a short silence, continued : – That’s the Scythian war. It’s all good, but not for those who take the rap with their own sides. And you are Prince Andgey Bolkonsky? - He shook his head. “It’s very hell, prince, it’s very hell to meet you,” he added again with a sad smile, shaking his hand.
Prince Andrei knew Denisov from Natasha's stories about her first groom. This memory both sweetly and painfully transported him now to those painful sensations about which he lately I haven’t thought about it for a long time, but they were still in his soul. Recently, so many other and such serious impressions as leaving Smolensk, his arrival in Bald Mountains, the recent death of his father - so many sensations were experienced by him that these memories had not come to him for a long time and, when they came, had no effect on him. him with the same strength. And for Denisov, the series of memories that Bolkonsky’s name evoked was a distant, poetic past, when, after dinner and Natasha’s singing, he, without knowing how, proposed to a fifteen-year-old girl. He smiled at the memories of that time and his love for Natasha and immediately moved on to what was now passionately and exclusively occupying him. This was the campaign plan he came up with while serving in the outposts during the retreat. He presented this plan to Barclay de Tolly and now intended to present it to Kutuzov. The plan was based on the fact that the French line of operations was too extended and that instead of, or at the same time, acting from the front, blocking the way for the French, it was necessary to act on their messages. He began to explain his plan to Prince Andrei.
“They can’t hold this entire line.” This is impossible, I answer that they are pg"og"vu; give me five hundred people, I will kill them, it’s veg! One system is pag “Tisan.”
Denisov stood up and, making gestures, outlined his plan to Bolkonsky. In the middle of his presentation, the cries of the army, more awkward, more widespread and merging with music and songs, were heard at the place of review. There was stomping and screaming in the village.
“He’s coming himself,” shouted a Cossack standing at the gate, “he’s coming!” Bolkonsky and Denisov moved towards the gate, at which stood a group of soldiers (an honor guard), and saw Kutuzov moving along the street, riding a low bay horse. A huge retinue of generals rode behind him. Barclay rode almost alongside; a crowd of officers ran behind them and around them and shouted “Hurray!”
The adjutants galloped ahead of him into the courtyard. Kutuzov, impatiently pushing his horse, which was ambling under his weight, and constantly nodding his head, put his hand to the cavalry guard’s bad-looking cap (with a red band and without a visor) that he was wearing. Having approached the honor guard of fine grenadiers, mostly cavaliers, who saluted him, he silently looked at them for a minute with a commanding stubborn gaze and turned to the crowd of generals and officers standing around him. His face suddenly took on a subtle expression; he raised his shoulders with a gesture of bewilderment.
- And with such fellows, keep retreating and retreating! - he said. “Well, goodbye, general,” he added and started his horse through the gate past Prince Andrei and Denisov.
- Hooray! hooray! hooray! - they shouted from behind him.
Since Prince Andrei had not seen him, Kutuzov had grown even fatter, flabby and swollen with fat. But those he knows white eye, and the wound, and the expression of fatigue in his face and figure were the same. He was dressed in a uniform frock coat (a whip hung on a thin belt over his shoulder) and a white cavalry guard cap. He, heavily blurring and swaying, sat on his cheerful horse.
“Whew... whew... whew...” he whistled barely audibly as he drove into the yard. His face expressed the joy of calming a man intending to rest after the mission. He took out left leg from the stirrup, falling with his whole body and wincing from the effort, he lifted it with difficulty onto the saddle, leaned his elbow on his knee, grunted and went down into the arms of the Cossacks and adjutants who were supporting him.
He recovered, looked around with his narrowed eyes and, glancing at Prince Andrei, apparently not recognizing him, walked with his diving gait towards the porch.
“Whew... whew... whew,” he whistled and again looked back at Prince Andrei. The impression of Prince Andrei's face only after a few seconds (as often happens with old people) became associated with the memory of his personality.
“Ah, hello, prince, hello, darling, let’s go...” he said tiredly, looking around, and heavily entered the porch, creaking under his weight. He unbuttoned and sat down on a bench on the porch.

The name sirens comes from the sirens from Greek mythology, as from a distance they can easily be confused with bathing people. However, the singing of the legendary sirens does not suit these animals in any way. Christopher Columbus was not the first person to see sirens, but he is known to have mentioned them in his diary in 1493. Sirens(lat. Sirenia) - herbivorous marine mammals, gentle creatures, absolutely safe and, moreover, practically silent.

Dugong

Sea, or Steller's, cows (Hydrodamalis), manatees (Trichechidae) and dugongs (Dugongidae) are representatives of three families of animals, united in a small order of sirens (Sirenia). They originated from proboscis animals; their most distant ancestor is considered to be Eotherium (terrestrial fossil animal). Another confirmation that sirens existed many millions of years ago and led a terrestrial lifestyle was recently received by American paleontologists who found in Jamaica the remains of the ancestor of the Steller's cow, which is at least 50 million years old. This discovery helped restore the evolutionary chain of transformation of land dwellers into sea dwellers. The skeleton of the fossil animal was more than 2 meters long, and its body, according to scientists, should have weighed at least 100 kg and had powerful, well-developed limbs. At the same time, its anatomical features allowed it to live in water. According to one scientific hypothesis, sea cows rushed from land to water for a new source of food - sea grass and gradually began to spend most of their lives there. Over time, manatees developed fins and their hind legs were replaced by a tail.

In the evolutionary series, modern mammals are between cetaceans and pinnipeds. In memory of their land-based ancestors, manatees retained lungs, limbs transformed into flippers, and a flat, rounded tail. It is noteworthy that three flat nails are preserved at the tips of their flippers, but on land these animals cannot move even by crawling.

Manatees are staunch vegetarians. Thanks to their very heavy skeleton, they easily sink to the bottom, where they feed on algae and herbs, eating huge amounts of them. Manatees grind their food with 20 teeth. The incisors are lost early, but in their place horny plates develop, with which animals deftly grasp and grind food. While feeding, they pull algae towards them with their flippers and, pressing an armful to their body, absorb the long green stems with constant appetite. Sometimes manatees even pluck some coastal plants. However, no matter how great their desire to eat a fresh twig, they cannot get out onto land. After eating it is time to rest. Manatees sleep in shallow water with their backs above the water and their tails on the bottom, or they hang in the water using densely intertwined algae as a hammock. They can be seen sleeping or dozing at any time of the day, but only in the most secluded and quiet places.

Typically, a female manatee gives birth to one baby every 3-5 years, very rarely twins. After mating, the male does not leave the female until the baby is born. Pregnancy lasts about 9 months. The peak birth rate occurs in April-May. Childbirth takes place under water. A newly born manatee is about 1 meter long and weighs 20-30 kg. Immediately after birth, the mother lifts the baby on her back to the surface of the water so that it takes its first breath. For about another 45 minutes, the baby usually remains lying on the mother’s back, gradually regaining consciousness, and then they are immersed in the water again.

A sea cow feeds her baby with milk underwater. Well-developed nipples located on the chest often misled many sailors, who mistook them for mermaids. Both parents take part in the initial upbringing of the calf, affectionately hugging it with flippers and rolling it on its back when it gets tired. Then, for two years, the baby remains under the watchful care of the female. Puberty in manatees it occurs at 3-4 years of age.

The manatee family has three species: American (Trichechus manatus), living along the coast from Florida to Brazil, African (T. senegalensis), living near river banks Equatorial Africa, and Amazonian (T. inunguis), which has chosen the Amazon, Orinoco and their tributaries.

The body length of manatees reaches 4 meters, they weigh about 400 kilograms, although individual males can reach 700. The body of the animals is spindle-shaped, ending with a horizontal rounded caudal fin. The forelimbs are made flexible pectoral fins, and in place of the hind ones there are only rudiments of the femur and pelvic bones. There is also no dorsal fin. The head is small, very mobile, without ears, with small eyes covered with a gelatinous mass. Studies have shown that manatees have poor vision. But they have sensitive hearing and, judging by the large olfactory lobes of the brain, a good sense of smell. Manatees have two distinctive features. Firstly, they have 6 cervical vertebrae, while other mammals have 7. And secondly, the heart of manatees, in relation to their body weight, is the smallest among all representatives of the animal world - it is 1,000 times lighter than their weight.

Manatees are very heat-loving creatures. If the water temperature drops below +8 degrees, they are doomed to death. Therefore, in winter they warm themselves in warm currents, flocking into larger flocks. These extremely peaceful animals also have enemies. In tropical rivers they are caimans, in the sea they are sharks. Usually slow, manatees, in defense, display activity that is rare for them.

But the greatest threat to the life of these already quite rare animals is still posed by humans, who are gradually displacing them from their ecological niche, thereby depriving them of their living space. Manatees are often destroyed for the sake of delicious meat and valuable fat used for the preparation of medicinal ointments and cosmetics, and this, despite the laws prohibiting their shooting and trapping, adopted in the USA back in 1893, and in Guyana in 1926.

The once calm waters of the local rivers, lakes and seas are now cut by boats and motor boats, and often peacefully grazing manatees fall under their propellers. Many die from their wounds, and the survivors have terrible scars on their backs. Fishing hooks and nets also cause great trouble for these animals. Relatively recently, special warning signs appeared on the coasts: “Caution! Manatee habitat! Cross very carefully!”

Apparently, people are still capable of learning from their mistakes, which means there is hope that these trusting and completely harmless creatures of Nature will continue to live on our planet.

Ksenia Cherkashina

Genus: Trichechus = Manatees

Species: Trichechus bernhardi Roosmalen, 2007 = Pygmy manatee

Species: Trichechus inunguis Natterer, 1883 = Amazonian manatee

Species: Trichechus manatus Linnaeus, 1758 = American manatee

Species: Trichechus senegalensis Link, 1795 = African manatee

Brief description of the squad

Sirens are secondary aquatic mammals (marine or freshwater), adapted to permanent life in the water; close to ancient ungulates. Body length is 2.5-5.8 m (in the extinct sea cow up to 7.2-10 m). Weight up to 650 kg (for a sea cow up to 4 tons).
Body massive fusiform. The neck is short and thick, but mobile. The head is relatively small, rounded with a relatively small mouth. Highly developed upper lip forms a soft “labial disk” - a kind of trunk, equipped with tactile sense organs. The mouth opening is located on the lower surface of the head. The external nasal openings open at the top of the head and are capable of closing. The eyes are small, with movable eyelids without eyelashes; the nictitating membrane is well developed. There are no auricles, the ear openings are very small. The forelimbs are five-fingered, turned into flippers. The hind limbs are reduced. The flippers move freely at the shoulder joint and, unlike cetaceans, are mobile at the elbow and wrist joints. Fingers dressed in common skin and are invisible from the outside. Skeletal-free horizontal caudal fin of triangular or round shape; it serves as a locomotor organ. Leather thick, covered with sparse bristly hairs. Subcutaneous fatty tissue is highly developed. There are numerous thick vibrissae on the lips. The two nipples are located in the chest area. Molars with a flat chewing surface, like those of ungulates; the stomach consists of several sections.
The stomach is complex. The intestine is very long. It exceeds the body length by 13-20 times. The lungs are simple, long and narrow, not divided into lobes. The brain is small with few convolutions; olfactory lobes are well developed. Eating underwater vegetation, live in herds, grazing in underwater “meadows”.
Distributed sirens in tropical waters Indian, Atlantic and eastern parts Pacific Oceans, as well as in the Amazon, Orinoco, and tropical rivers West Africa. Extinct sea ​​cow lived in the Bering Sea. Locals hunt sirens for their tasty meat and tough skin.
Fossil representatives order are known from the Middle Eocene of Egypt and Jamaica. The most ancient of them, although they had a number of primitive features (complete dental system, absence of horny plates, fairly well-developed pelvis, vestigial hind limbs), were true aquatic animals. The structure of their skull and teeth shows similarities with primitive proboscideans and hyraxes. Apparently, the ancestors of sirens were land animals close to the original forms of proboscideans, hyraxes and ungulates.
Manatee family - Manatidae- 3 species - lives off the coast of West Africa and the east South America(near the Antilles). In the dugong family - Halicoridae one species common in coastal strip Indian Ocean. In 1741, zoologist Steller discovered Steller's cow near the Commander Islands - Rhytina stelleri. Exterminated by hunters: the last specimen was killed in 1768