Why is a whale classified as a mammal? Is a whale a fish or a mammal? More interesting articles
A whale is a marine animal of the chordate type, class mammals, order Cetacea. The whale received its modern name, consonant in many languages, from the Greek word kitoc, literally meaning “sea monster.”
Anatomically, the whale has teeth, but in some species they are in an undeveloped state. In toothless baleen whales, teeth are replaced by bony plates called baleen and adapted for straining food.
And only representatives of toothed whales grow identical cone-shaped teeth.
The whale's spine can contain from 41 to 98 vertebrae, and thanks to the spongy structure of the skeleton, elastic intervertebral discs give the animal's body special maneuverability and plasticity.
There is no cervical interception, and the head smoothly merges into the body, which noticeably tapers towards the tail. The whale's pectoral fins are modified and turned into flippers that perform the function of steering, turning and braking. The tail section of the body is flexible and muscular, has a slightly flattened shape and performs the function of a motor. At the end of the tail there are blades that are horizontal.
Most species of whales have an unpaired dorsal fin, which acts as a stabilizer when moving through the water column.
The skin of a whale is smooth, hairless, only single hairs and bristles grow on the face of baleen whales, similar to the whiskers of land animals.
The color of the whale can be monochromatic, spotted or counter-shaded, when the top of the animal is dark and the bottom is light. In some species, the color of the body changes with age.
Due to the absence of olfactory nerves, whales have almost completely lost their sense of smell. Taste buds are poorly developed, so unlike other mammals, whales can only distinguish the salty taste. Whales have poor eyesight, most of these animals are myopic, but they have conjunctival glands that are absent in other animals.
In terms of whale hearing, the complex anatomy of the inner ear allows whales to detect sounds ranging from 150 Hz to the lowest ultrasonic frequencies. And due to the richly innervated skin, all whales have an excellent sense of touch.
Whales communicate with each other. The absence of vocal cords does not prevent whales from speaking and making special sounds using their echolocation apparatus. The concave bones of the skull, together with the fat layer, act as a sound lens and reflector, directing a beam of ultrasonic signals in the desired direction.
Most whales are quite slow, but if necessary, a whale's speed can be 20 - 40 km/h.
The lifespan of small whales is about 30 years, large whales live up to 50 years.
Where do whales live?
Whales live in all oceans. Most species of whales are gregarious animals and prefer to live in groups of several tens or even thousands of individuals. Some species are subject to constant seasonal migrations: in winter, whales swim to warm waters where they give birth, and in summer they fatten in temperate and high latitudes.
What does a whale eat?
Most whales eat a certain type of food:
- planktivores eat exclusively plankton;
- teutophagous prefer to eat cephalopods;
- ichthyophages they eat only live fish;
- saprophages (detritivores) consume decomposed organic matter.
And only one animal from the order of cetaceans, the killer whale, feeds not only on fish, but also on pinnipeds (seals, sea lions,) as well as other whales, dolphins and their calves.
Killer whale swims after a penguin
Types of whales with photos and names.
Modern classification divides the order of cetaceans into 2 main suborders:
- toothless or mustachioed whales (Mysticeti);
- toothy whales (Odontoceti), which includes dolphins, killer whales, sperm whales and porpoises.
The order Cetacea forms 38 genera, which include over 80 known species. Among this variety, several varieties can be distinguished:
- , aka humpback or long-armed minke whale(Megaptera novaeangliae)
got its name from the convex fin on its back, reminiscent of a hump. The body length of the whale reaches 14.5 meters, in some specimens - 18 meters. The average weight of a humpback whale is 30 tons. The humpback whale differs from other representatives of the minke whale family in its shortened body, variety of colors and several rows of warty, leathery protrusions on the top of its head. Humpback whales live throughout the world's oceans, except the Arctic and Antarctic. Representatives of the North Atlantic population feed exclusively on fish: navaga, pollock, herring, and haddock. The remaining whales eat small crustaceans, various shellfish and small schooling fish.
- Gray whale (California whale) (Eschrichtius robustus, Eschrichtius gibbosus)
the only species of whale that practices eating food from the bottom of the ocean: the animal plows the silt with a special keel-shaped outgrowth located under the lower jaw. The gray whale's diet consists of a variety of bottom-dwelling organisms: annelids, bivalves and other molluscs, crayfish, egg capsules and sea sponges, as well as small fish species. Gray whales in adulthood have a body length of up to 12-15 m, the average weight of a whale varies from 15 to 35 tons, with females being larger than males. The body is brown-gray or dark brown, reminiscent of rocky shores in color. This species of whale lives in the Sea of Okhotsk, Chukchi and Bering Seas, and in winter migrates to the Gulf of California and to the southern shores of Japan. Gray whales are record holders among animals for the duration of migrations - the distance covered by animals can reach 12 thousand km.
- bowhead whale (polar whale) (Balaena mysticetus)
long-lived among mammals. The average age of a polar whale is 40 years, but the known scientifically proven fact of longevity is 211 years. This is a unique species of baleen whale that spends its entire life in the cold waters of the Northern Hemisphere, often making its way like an icebreaker. The whale fountain rises to 6 m in height. The body length of mature females reaches 20-22 meters, males - 18 meters. The weight of a whale is from 75 to 150 tons. The animal's skin color is usually gray or dark blue. The belly and neck are lighter in color. An adult bowhead whale consumes almost 2 tons of various foods every day, consisting of plankton (crustaceans and pteropods).
- Sperm whale (Physeter macrocephalus)
the largest representative of toothed whales, and females are much smaller than males and have a body length of no more than 15 meters. The male whale grows up to 20 meters in length. The maximum weight of females reaches 20 tons, males - 50 tons. Sperm whales have such a distinctive appearance that they cannot be confused with other cetaceans. The giant head makes up over 35% of the length of the body, and, when viewed from the side, the sperm whale's muzzle looks like a slightly beveled rectangle. In the recess at the bottom of the head there is a mouth lined with 20-26 pairs of cone-shaped teeth. The weight of 1 whale tooth reaches 1 kilogram. The wrinkled skin of the sperm whale is often dark gray with a blue tint, although dark brown and even black individuals are found. Being a predator, the sperm whale hunts squid, cuttlefish, large fish (including some species), and also swallows all sorts of objects found in the ocean: empty bottles, rubber boots, toys, coils of wire. Sperm whales live throughout the world's oceans, but are more common in tropical waters than in cool ones. Most of the population is distributed off the coast of the Black Continent and the eastern coast of Asia.
- (Balaenoptera physalus)
the second largest animal on the planet. The length of an adult whale is 24-27 m, but thanks to its slender physique, the whale weighs only 40-70 tons. A distinctive feature of fin whales is the asymmetrical coloration of the muzzle: the right part of the lower jaw is white, and the left is dark. The whale's diet consists of small crustaceans. Fin whales live in all oceans: in winter they inhabit the waters of moderately warm zones, and in the warm season they swim to the waters of the Arctic and Antarctic.
- Blue whale (blue whale, vomited)(Balaenoptera musculus)
not only the largest whale in the world, but also the largest animal on our planet. The length can reach 33 meters, and the weight of the blue whale reaches 150 tons. This animal has a relatively slender build and a narrow muzzle. The body color within the species is uniform: most individuals are gray with a blue tint and gray spots scattered throughout the body, making the animal’s skin appear marbled. The blue whale feeds mostly on plankton and inhabits the entire World Ocean.
- Dwarf right whale (dwarf right whale, short-headed right whale)(Caperea marginata)
The smallest species of the suborder of baleen whales. The body of an adult does not exceed 4-6 m in length, and the whale’s body weight barely reaches 3-3.5 tons. Skin color is gray with dark spots, sometimes black. It is distinguished by a wave-like mode of movement, unusual for whales, and feeds on plankton. The pygmy whale is one of the rarest and smallest species of whales, living mainly in the waters of southern Australia and New Zealand.
This article is dedicated to amazing and unusual animals, which some still consider to be fish - cetaceans. Why be surprised if even in children's fairy tales such a phrase as “whale fish” sounds! “Cetaceans” (from the Latin word Cetacea) are a fairly large order of mammals that have evolved and adapted exclusively for life in water.Order Cetaceans and its representatives
The body structure of cetaceans is very similar to that of fish. In everyday life, all these animals are usually called whales. The exception to the order under consideration is the family of porpoises and dolphins. The scientific Latin name for this order is “cetus”. The Russian word “whale” comes from Greek and literally means “sea monster”.
In general, cetaceans are the largest animals of all the animals that live on our planet. As for the origin of these creatures, it is believed that they descended from artiodactyl land mammals, which were able to further adapt to a semi-terrestrial - semi-aquatic lifestyle about fifty million years ago. In the modern world there is a wide variety of these fish-like marine animals.
The blue whale is the largest whale, the largest living animal, and probably the largest animal to ever live on Earth.
The entire large order of cetaceans is usually divided into two suborders: toothed whales (Odontoceti) and toothless or otherwise baleen whales (Mysticeti). Representatives of these suborders differ significantly from each other not only in their appearance, way of life, but also in their internal structure.
The order Cetacea unites thirty-eight genera, which include more than eight dozen species of marine mammals. About thirty species of cetaceans can be found in Russia. In order for you to get your bearings a little, to understand what these animals are and who belongs to the cetaceans, let’s look at their accepted classification:
- Suborder Odontoceti - Odontoceti divided into:
— Family Delphinidae — Dolphinidae is quite numerous and includes killer whales, white-sided dolphins, bottlenose dolphins;
Bottlenose dolphin (or bottlenose dolphin) with calf
- Family Phocoenidae - Porpoises includes four species of porpoises, the finless porpoise (Neophocaena phocaenoides) and the white-winged porpoise (Phocoenoides dalli);
- Family Monodontidae - Narwhals includes the beluga whale (Delphina pterusleucas) and the unicorn (Monodon) which includes the narwhal (Monodon monoceros);
Narwhal
Beluga whales
— Family Physeteridae — Sperm whales. This family includes the sperm whale (Physeter macrocephalus);
- Family Kogiidae - Dwarf sperm whales. Sometimes this family is referred to as the sperm whale family. It includes the dwarf sperm whale (Kogia breviceps) and the little sperm whale (Kogia simus);
Sperm whale
- Superfamily Platanistoidea - River dolphins includes the Family Iniidae, which in turn includes the Amazonian dolphin (Inia geoffrensis);
— Family Platanistidae. The Gangetic dolphin (Platanista gangetica) belongs to this Family. This species is sometimes divided into two subspecies;
— The family Pontoporiidae is represented by the La Plata dolphin (Pontoporia blainvillei);
— Family Lipotidae. This includes the Chinese river dolphin (Lipotes vexillifer);
Amazon river dolphin
- Family Ziphidae - Beaked. It includes swimmers or otherwise Berardius - only two species, bottlenose whales (Hyperoodon), also two species, belted whales (Mesoplodon) - fourteen species, longman's whale (Indopacetus pacificus), beaked whale (Ziphius cavirostris) and Tasmanian beaked whale (Tasmacetus shepherdi ).
Beaked whale
- Suborder Mysticeti - Toothless whales divided into:
— Family Balaenidae — Right whales. It includes three species of southern right whale (Eubalaena) and the bowhead whale (Balaena mysticetus);
— Family Eschrichtiidae — Gray whales, which actually includes the gray whale itself (Eschrichtius robustus);
- Family Balaenopteridae - Minke whales includes the subfamily Balaenopterinae, which includes eight species of minke whales and the subfamily Megapterinae, which includes the humpback whale (Megaptera novaeangliae);
- Family Neobalaenidae, which includes a single representative - the dwarf right whale (Caperea marginata).
humpback whale
Appearance and lifestyle of animals that make up the order Cetaceans
As you yourself have already understood, the cetacean order is a very large order, which includes dozens of species of different representatives of these marine animals. They are all significantly different from each other, however, they have a lot in common. The most common and prominent representatives of this order have been familiar to us since childhood. After all, it is not at all necessary to be an expert in order to distinguish, for example, a whale from a dolphin.
The smallest cetaceans are Hector's dolphin and the white-bellied dolphin. The length of these “babies” is a maximum of 120 cm, but they weigh only 40 – 45 kg. The largest cetacean is the blue whale. The length of this giant’s body can reach as much as 33 meters, and its weight can be more than 150 tons! Despite all the differences between cetaceans and fish, they are united by certain similarities in appearance, habitat, lifestyle, and much more. Outwardly, these animals are very similar to fish, but differ primarily in that they are warm-blooded and breathe with lungs rather than gills. Their body temperature ranges from 36 to 40 C.
Great killer whale
The peculiarities of the respiratory and circulatory systems allow them to continuously remain under water, once making a supply of air, for up to an hour and a half! The skin of cetaceans, unlike most fish, is devoid of scales and contains remnants of hair (vibrissae). The structure of their bodies is streamlined, which allows them to experience the least friction, and therefore water resistance when swimming. This is also facilitated by their smooth, firm and elastic skin, completely devoid of hair. The color of numerous species of cetaceans varies from solid to spotted or counter-shadow (dark back and light belly). In some species it may change with age.
Like land mammals, the young of animals from the order Cetaceans do not develop in the external environment, but in utero, and after birth they are fed with milk. Most species are herd (collective) animals and therefore gather in groups of several tens, hundreds and even thousands of individuals. Cetaceans are distributed throughout the world, they can be found in all oceans and in most seas. Among them there are heat-loving species, i.e. tropical and subtropical, cold-loving species of polar and subpolar waters, as well as species with a wide habitat.
Gangetic river dolphins
Cetaceans are found both in the open sea and very close to the coasts. Some species can even enter rivers and live there for a long time. Some species of these mammals are characterized by seasonal migrations over short distances, others by long migrations covering many thousands of kilometers, and still others prefer an almost sedentary or nomadic lifestyle within a small water area, that is, “not far from home.”
According to the method and nature of feeding, cetaceans are divided into four groups:
- ichthyophages - species that feed mainly on fish;
- planktivores - species that typically feed on plankton;
- saprophages - species that feed on decaying organic remains and substances;
- Teutophagous - species that consume various cephalopods.
Thus, the diet of different species of cetaceans is not distinguished by gastronomic diversity and is very specialized, however, among the representatives of the genus in question, there is only one that periodically and regularly feeds not only on fish and, but also on warm-blooded creatures, such as seals, birds, and even their own kind . This species is the killer whale.
Great killer whale
Cetaceans live relatively long: small species - up to thirty years, large ones - up to about fifty.
It must be said that the animals that make up the order Cetaceans are not only numerous, but also very diverse, unusual and interesting, and therefore deserve attention. These articles will tell you about some species of marine mammals:
Suborder Toothed whales
Unlike baleen whales, they have single-peaked teeth and a small mouth and tongue. They navigate underwater and find food mainly using echolocation and excellent hearing. They use complex audio alarms.
Most toothed whales are inhabitants of the open seas and oceans. Almost all of them swim excellently and catch fast-moving prey - squid, etc. This group includes sperm whales, dolphins, etc.
Sperm whale - one of the large toothed whales 20 m long, the female is smaller (15 m). Its large head reaches 1/3 of its body length. The dorsal fin has a thick, low hump, followed by several smaller humps; pectoral fins with rounded ends. The color of the head, back and sides is dark brown or black, the belly is light.
The sperm whale is distributed throughout the World Ocean, in our country - in the Barents Sea, off the coast of Kamchatka. It feeds on cephalopods and fish (pollock, cod, spiny sharks, etc.), diving to a depth of 500 m or more.
Sperm whales are of commercial importance; they are caught for their oil, spermaceti, a waxy substance found in the fat pad on the head.
common dolphin
common dolphin- a small toothed cetacean with a body length of 160–260 cm. On the back there is a sickle-shaped fin.
The back and fins are dark, the belly is white; there are gray stripes on the sides. Widely distributed in the open seas of the World Ocean, found in the territorial waters of our country: in the Black, Baltic, Okhotsk and Japanese seas (see textbook figure, p. 231).
White-sided dolphins live in herds, swim very quickly, at a speed of 55 km/h, and can jump to a height of 5 m, and horizontally - up to 9 m. They feed on fish and cephalopods. Echolocation is well developed and they have vocal signaling. The female gives birth to a single cub, 80–90 cm long, after 10 months of pregnancy. Breastfeeds with milk for 5 months.
Dolphins treat humans peacefully and never attack. For a long time, these cetaceans were an important commercial target. Currently, their numbers have sharply decreased, so fishing is prohibited everywhere.
Great killer whale
Great killer whale- a large predatory dolphin, body length 5–10 m, weight 8 tons. The head is short, without a beak, the dorsal and pectoral fins are very large. The upper part of the body is black or black-gray, the lower part is white. There are large white spots on the sides of the back of the body.
Distributed in all seas of the Arctic Ocean and in all Far Eastern seas. Stays in groups, swims quickly, reaching speeds of up to 19 km/h. It feeds on fish (cod, sardines, sharks, etc.), cephalopods. It attacks seals, seals, dolphins of other species and even whales.
It does not attack humans, but it also does not feel fear of them when approaching ships, boats and boats.
It tolerates captivity well and is trainable.
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Humanity began to ask the question of who a whale is, a fish or an animal, long before the formation of modern natural sciences. As the largest of all creatures living under water, this giant simply could not help but delight everyone who had the chance to see it.
Is a whale a fish or an animal?
Of course, today, thanks to modern knowledge about the structure of cetaceans and their origin, it is no longer difficult to give an exact answer to this question that has tormented man for so long. So, who exactly is he? This is a mammal whose ancestors once upon a time, for certain reasons, returned from land to water. What forced them to do this - whether it was competition from other animal species, or a sharp decrease in food in their habitat - is not known for certain. However, in the end, they found a new home for themselves there and, having successfully adapted, over time evolved into the form under which we know these creatures today.
Of the land animals currently living on the planet, the closest relatives of cetaceans are hippos, which are indeed similar to them in many respects in behavior and in their mutual love of water.
Cetaceans - general facts
In their family, whales are its only representatives. However, the same dolphins and porpoises also belong to marine mammals. What makes it possible to distinguish whales into a separate family? The main differences are as follows:
- Unlike fish, warm-blooded cetaceans. Therefore, to maintain core body temperature, they need a very thick subcutaneous fat layer.
- Second feature lies in the inability of whales to obtain oxygen directly from the water. To replenish its supply, they need to periodically rise to the surface.
- All cetacean mammals. And although the process of feeding babies with milk has undergone changes during evolution, its essence has remained the same.
The cetacean family is divided into three groups:
The whale is the largest living mammal. Its adult specimen can easily reach 25 meters in length. It weighs on average from 90 to 110 tons. These animals inhabit almost all the oceans of the Earth, however, due to their warm-blooded nature, they are prone to frequent migrations. They prefer to wait out cold winters closer to the tropics.
Based on skin color, whales are divided into blue and gray. The gray ones are presumably more ancient. Judging by some of the remains of these animals, their representatives inhabited the planet about 30 million years ago. Then they were distributed almost throughout the globe; Nowadays, gray whales are mostly seen in the North Pacific Ocean. They prefer to live in small groups of several individuals. There are also solitary whales, but this is rather an exception. Whales have incredibly strong family ties and communication with other members of their species is very important to them.
Blue whales are larger in size than gray whales, as well as any other mammal on the planet. With their size, they are a living reminder of those giants who once inhabited the land. They are not very fond of people, preferring to stay away from the coast and remaining mostly in the open ocean. As befits such a giant, the blue whale is quite slow. The average speed of its movement is about 10 km/h, however, if the animal is threatened, it can increase three times.
The number of animals has reached critically low levels many times. Often the reason for this was a person who mercilessly exterminated them for their valuable meat and fat. But the very specifics of cetacean reproduction do not contribute to the rapid restoration of population numbers. Offspring, as a rule, are born no more than once or twice a year. In this case, the female gives birth to only one kitten; sometimes it happens that there are two. The duration of pregnancy can vary from 9 to 18 months depending on the subspecies.
Naturally, with such vulnerability, the female protects the cub like the apple of her eye. The cubs also grow very quickly - after just six months they can already reach 14 meters in length and weigh up to 25 tons. Puberty in whales occurs when they reach the age of five, but a whale is considered truly adult only at 15 years of age.
What does a whale eat?
So what do whales eat? Their diet is highly specialized and depends entirely on the species. They can be planktivores and eat plankton, teutophages and eat shellfish, ichthyophages (use fish as a food source) and sacrophages (eat algae). Animals swallow their prey whole, without preliminary chewing. Toothed whales either grab it and hold it with their teeth, or use their tongue to suck in several fish at a time. Baleen whales pass large portions of food through a filter called "baleen". The only representative of cetaceans that regularly feeds on warm-blooded animals is the killer whale.
Rice. 1. Sequence of evolution of early cetaceans" border="0">
New Zealand phylogeneticists have shown that a fossil pygmy whale that lived 7–8 million years ago may well be the ancestor of the modern pygmy whale living in the ocean near Antarctica. This work has serious methodological significance: the fact is that the hypothesis of direct ancestral relationships between two genera, separated by several million years, is quite unusual for modern paleontology. It is customary to regard even very closely related organisms as sister groups, avoiding claims of direct descent of one from the other. However, it is possible that in some cases such caution may be unnecessary. The fossil record is in some places complete enough to contain segments of the actual course of evolution (even if short).
The history of cetaceans (Cetacea) provides enormous opportunities for studying major evolutionary changes. A whale is not a fish, but a mammal. Mammals appeared on land. This means that whales evolved from some other land mammals. But from which ones? And what did the transitional forms look like? These questions intrigued Charles Darwin - in the book “The Origin of Species by Means of Natural Selection” they were given a lot of attention. But they were solved only at the very end of the 20th century, thanks to the combined efforts of paleontologists and geneticists. According to modern ideas, the ancestors of whales belonged to the order Artiodactyla, which includes pigs, hippopotamuses, deer, antelopes, giraffes, goats and their various relatives, including the domestic cow.
According to molecular data, the closest living relatives of cetaceans are hippopotamuses. However, the evolutionary branches of hippopotamuses and whales diverged long ago. The ungulate ancestor of cetaceans most likely was similar in appearance and lifestyle not to the hippopotamus, but to the African water deer ( Hyemoschus aquaticus) is a small graceful animal, beautifully described by Gerald Durrell in the book “A Zoo in My Luggage”.
It is noteworthy that the “transformation” of land animals into whales began and ended in the Eocene period (56–34 million years ago). On the scale of Earth's history, this is fast. At the beginning of the Eocene, we see small ungulates of a rather ordinary appearance, only spending part of their time in the water. At the end of the Eocene, these were already very large fish-like creatures living in the ocean and unable to go onto land; It has been noted more than once that such late Eocene whales as Basilosaurus must have been both in size and general appearance reminiscent of the legendary sea serpents. Moreover, the transitional states are now well documented paleontologically (Fig. 1). This is how you can “observe” macroevolution.
We must not forget that evolution always occurs not only in time, but also in space. As far as is now known, all land and freshwater predecessors of whales lived on one single continent - the Indian. This is the peculiarity acquired by the mammal fauna of India, which was then about as isolated from all other land as Australia. The worldwide distribution of cetaceans arose only as a result of their release into the ocean.
At the very end of the Eocene, cetaceans split into two branches: toothed whales (Odontoceti) and baleen whales (Mysticeti). The hero of Herman Melville’s great novel “Moby Dick” speaks disparagingly about baleen whales, calling the bowhead whale related to them “a despicable monster.” But from the point of view of evolutionary morphology, baleen whales are even more interesting. All modern baleen whales are completely toothless as adults. Their baleen is a system of plates consisting of a horny substance (much like our fingernails) that serves to filter water. Such a method of feeding, unusual for mammals, could not but lead to great anatomical changes, especially in the skull. In addition, the very fact that the largest modern animals (and most likely the largest animals in general: the blue whale is larger than any known dinosaur) feed on planktonic crustaceans, euphausiids, which you cannot really see without a binocular, is noteworthy. It was not for nothing that the French evolutionist Émile Guyénot called baleen whales “a living paradox of nature.”
It is not surprising that cetaceans serve as good material for solving various evolutionary problems, including those of a very general nature.
One such problem concerns the relationship between ancestors and descendants. It is obvious that the fossil record is extremely incomplete. It follows from this that fossil forms, even close ones and located “as they should” in the earth’s layers, are not necessarily direct ancestors and descendants of each other. The great popularizer of biology, Richard Dawkins, in his book “The Greatest Show on Earth,” explains this precisely using the example of the origin of whales. He gives there a diagram of the family relationships of cetaceans (vaguely reminiscent of Fig. 1) and comments on it as follows:
“Notice the care with which the diagram is drawn. Any author is tempted (authors of old books often succumbed to this temptation) to depict a sequence of fossil animals, connected by arrows, from ancient to young. But no one can say for sure that Ambulocetus descended from Pakicetus, A Basilosaurus- from Rhodocetus. Instead, it is cautiously suggested that whales evolved from an animal related to Ambulocetus, similar to him, perhaps from him.”
The outstanding paleontologist Alexei Petrovich Bystrov (Shatrov’s prototype from I. A. Efremov’s story “Starships”) wrote on the same topic: “We must admit that we know a significantly smaller number of extinct forms than actually existed; the vast majority of them have disappeared without a trace, and looking for them in the ground is like looking for the skeleton of Savonarola in the cemeteries of Florence.”
In modern phylogenetics (the science of the related relationships of organisms), cladistics almost reigns supreme - a doctrine that builds a system of living nature solely on the basis of kinship and according to very strict rules. The paradox is that in cladistics, which generally does not recognize other systematic criteria other than kinship, it is precisely impossible to correctly state a hypothesis of the form “from organism A came organism B.” The principles for constructing evolutionary trees there are such that it is simply technically impossible. At best, we can talk about sister groups descending from an unconditionally implied, perhaps close, but unknown to us common ancestor.
An example of such caution in the popularization of science is a common disclaimer about the origin of man: they say that he did not descend from a monkey, but from a “common ancestor” with a monkey. Although who, besides another monkey, could this ancestor be?
In modern scientific publications (especially those specifically devoted to phylogenetics), talking about direct ancestors and descendants, if not prohibited, is, in any case, considered bad form, a sign of either unprofessionalism or great extravagance.
But is this attitude always fair? After all, it can’t be that no one’s real ancestors could be discovered at all never. Meanwhile, cladistics implicitly imposes just such a thesis. Its formal apparatus does not allow calling an ancestor an ancestor, even if one is found.
If this can be tested at all, then mammals living during the Cenozoic era (that is, after the extinction of the dinosaurs) are undoubtedly good candidates for such testing. First, most fossil Cenozoic mammals belong to modern orders, and many even belong to modern families. This makes their reconstruction incredibly easier compared, for example, with some armored agnathans that have no close modern relatives. Secondly, there are simply a lot of remains of Cenozoic mammals, because they lived relatively recently (on the scale of geological eras, of course). Thirdly, the anatomy of mammals is quite rich - there are so many features in one skull! - and thoroughly studied. This is an ideal material for testing hypotheses about family relationships.
Well, the evolution of whales entirely dates back to the Cenozoic. And in the fossil state they are well preserved.
Biologists from the University of Otago, located in the city of Dunedin on the South Island of New Zealand (University of Otago, Dunedin, Otago, New Zealand), decided to study in detail the problem of related relationships using the example of the family of dwarf whales (Neobalaenidae), belonging to the suborder of baleen whales (Mysticeti) .
This family includes only one modern species - the dwarf whale Caperea marginata(Fig. 2). It lives in the Southern Ocean, that is, at all longitudes around Antarctica. This is the smallest of the baleen whales. However, everything is relative here: baleen whales are, in principle, large animals, and even a dwarf whale can reach a length of six meters. It is small in number, relatively little known, and has never been fished. And its fossil relatives were also unknown - until recently.
In 2012, Italian paleontologist Michelangelo Bisconti described a fossil of a dwarf whale called Miocaperea pulchra(M. Bisconti, 2012. Comparative osteology and phylogenetic relationshipsof Miocaperea pulchra, the first fossil pygmy right whale genus and species (Cetacea, Mysticeti, Neobalaenidae)). This whale lived during the Miocene period, 7–8 million years ago. Its remains were found in Peru. The marine fauna to which it belongs is Pacific. In addition to whales, there are also other mammals: dolphins, pinnipeds and even such unusual creatures as sea sloths. The Miocene dwarf whale was very similar to the modern one, judging by the well-preserved skull (Fig. 3). They differ in some details of the auditory department, features of the location of the jaw and neck muscles, and also - this is perhaps the most interesting - in the number of baleen plates. The Miocene dwarf whale has a third less of them than the modern one. The meaning of this feature is not entirely clear; This is probably due to some differences in the way of eating. The modern gray whale has approximately the same number of plates as the Miocene dwarf whale, which feeds not on plankton (like the vast majority of baleen whales), but on benthos, that is, bottom-dwelling organisms.
As is now common practice, Bisconti places both pygmy whales on the pedigree chart as sister groups. This means that they are closer relatives to each other than any other two whales - no more and no less. Who came from whom is, as it were, unknown.
New Zealand biologists decided to build the evolutionary tree of dwarf whales anew - very carefully, using as many features as possible. The peculiarity was that the young individual of the modern dwarf whale was considered separately, as an independent operational unit, within the framework of the analysis, equal in rights not only with the fossil whale, but also with the adult individual of its species. In other words, the task was to determine the “affinity” of three forms: (1) the adult modern pygmy right whale, (2) the juvenile modern pygmy right whale, and (3) the Miocene pygmy right whale - as if all three were separate species. The approach to the material was very serious: the authors studied 35 skeletons of young individuals of the modern dwarf whale (although of varying degrees of completeness). And evolutionary trees were built according to the strictest rules, using modern programs, and even in slightly different ways.
The results were remarkable. In most trees, the Miocene whale falls between the juvenile and adult modern whales (Fig. 4). If we translate this into the language of common sense, this result means that the species Miocaperea pulchra appeared on the cladistic tree within the species Caperea marginata. This is an indicator of the closest relationship imaginable.
Only the Miocene dwarf whale lived, as we know, 7–8 million years earlier than the modern one. Obviously, the rate of evolution in the Neobalaenidae family was very low, which is why it has changed little.
The New Zealand authors begin their article by formally distinguishing two types of relationships between groups of organisms: “ancestor–descendant relationships” (ADRs) and “sister-group relationships” (SGRs). Conclusion: data analysis by species Miocaperea pulchra And Caperea marginata produces a pattern that is consistent with ADRs. In other words, Miocaperea pulchra may well be a direct ancestor Caperea marginata.
Truly a very complex way of saying that one animal came from another! But that’s exactly what they say.
I think this story with dwarf whales is instructive in two respects. First, the common claim that we never see immediate ancestors and descendants in the fossil record is an exaggeration. Sometimes we still see it. The fossil record is indeed very incomplete, but some fragments of the actual course of evolution (though usually short) can be reflected in it. Without any reservations about “common ancestors”.
Second: in this example we see how high the requirements for statements of kinship are in modern biology. About kinship in general, and about ancestral relationships in particular. To even suggest (in a scientific article) that one animal is a direct descendant of another requires multi-stage checks and the strictest logical correctness.
Well, we’ll see whether such work will lead to another reform of phylogenetic methods.