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Cetacean Genera
Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel themselves through the water with powerful up-and-down movements of their tail, which ends in a paddle-like fluke, using their flipper-shaped forelimbs to steer. While the majority of cetaceans live in marine environments, a small number reside solely in brackish or fresh water. Having a cosmopolitan distribution, they can be found in some rivers and all of Earth's oceans, and many species migrate throughout vast ranges with the changing of the seasons. Cetaceans are famous for their high intelligence, complex social behaviour, and the enormous size of some of the group's members. For example, the blue whale reaches a maximum confirmed length of and a weight of 173 tonnes (190 short tons), making it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eocene
The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes from the Ancient Greek (''Ēṓs'', 'Eos, Dawn') and (''kainós'', "new") and refers to the "dawn" of modern ('new') fauna that appeared during the epoch.See: *Letter from William Whewell to Charles Lyell dated 31 January 1831 in: * From p. 55: "The period next antecedent we shall call Eocene, from ήως, aurora, and χαινος, recens, because the extremely small proportion of living species contained in these strata, indicates what may be considered the first commencement, or ''dawn'', of the existing state of the animate creation." The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isoto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mysticeti
Baleen whales (), also known as whalebone whales, are marine mammals of the parvorder Mysticeti in the infraorder Cetacea (whales, dolphins and porpoises), which use baleen plates (or "whalebone") in their mouths to sieve plankton from the water. Mysticeti comprises the families Balaenidae (right and bowhead whales), Balaenopteridae ( rorquals), Eschrichtiidae (the gray whale) and Cetotheriidae (the pygmy right whale). There are currently 16 species of baleen whales. While cetaceans were historically thought to have descended from mesonychians, molecular evidence instead supports them as a clade of even-toed ungulates (Artiodactyla). Baleen whales split from toothed whales (Odontoceti) around 34 million years ago. Baleen whales range in size from the and pygmy right whale to the and blue whale, the largest known animal to have ever existed. They are sexually dimorphic. Baleen whales can have streamlined or large bodies, depending on the feeding behavior, and two l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carnivorous
A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly muscle, fat and other soft tissues) as food, whether through predation or scavenging. Nomenclature Mammal order The technical term for mammals in the order Carnivora is ''carnivoran'', and they are so-named because most member species in the group have a carnivorous diet, but the similarity of the name of the order and the name of the diet causes confusion. Many but not all carnivorans are meat eaters; a few, such as the large and small cats (Felidae) are ''obligate'' carnivores (see below). Other classes of carnivore are highly variable. The ursids (bears), for example: while the Arctic polar bear eats meat almost exclusively (more than 90% of its diet is meat), almost all other bear species are omnivorous, and one species, the gia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Streamlined
Streamlines, streaklines and pathlines are field lines in a fluid flow. They differ only when the flow changes with time, that is, when the flow is not steady flow, steady. Considering a velocity vector field in three-dimensional space in the framework of continuum mechanics: * Streamlines are a family of curves whose tangent vectors constitute the velocity vector field of the flow. These show the direction in which a massless fluid element will travel at any point in time. * Streaklines are the Locus (mathematics), loci of points of all the fluid particles that have passed continuously through a particular spatial point in the past. Dye steadily injected into the fluid at a fixed point (as in dye tracing) extends along a streakline. * Pathlines are the trajectory, trajectories that individual fluid particles follow. These can be thought of as "recording" the path of a fluid element in the flow over a certain period. The direction the path takes will be determined by the stre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porpoises
Porpoises () are small dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and belugas than to the true dolphins. There are eight extant species of porpoise, all among the smallest of the toothed whales. Porpoises are distinguished from dolphins by their flattened, spade-shaped teeth distinct from the conical teeth of dolphins, and lack of a pronounced beak, although some dolphins (e.g. Hector's dolphin) also lack a pronounced beak. Porpoises, and other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulates. Porpoises range in size from the vaquita, at in length and in weight, to the Dall's porpoise, at and . Several species exhibit sexual dimorphism in that the females are larger than males. They have streamlined bodies and two limbs that are modified into flippers. Porpoises use echolocation as their primary sensory system. Some species are well adapt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dolphin
A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the brackish dolphins), and possibly extinct Lipotidae (baiji or Chinese river dolphin). There are 40 extant species named as dolphins. Dolphins range in size from the and Maui's dolphin to the and orca. Various species of dolphins exhibit sexual dimorphism where the males are larger than females. They have streamlined bodies and two limbs that are modified into flippers. Though not quite as flexible as Pinniped, seals, they are faster; some dolphins can briefly travel at speeds of or leap about . Dolphins use their conical teeth to capture fast-moving Predation, prey. They have well-developed hearing which is adapted for both air and water; it is so well developed that some can survive even if they are blind. Some species are w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Artiodactyla
Artiodactyls are placental mammals belonging to the order (biology), order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof). The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, most perissodactyls bear weight on an odd number of the five toes. Another difference between the two orders is that many artiodactyls (except for Suina) digest plant cellulose in one or more stomach chambers rather than in their intestine (as perissodactyls do). Molecular biology, along with new fossil discoveries, has found that cetaceans (whales, dolphins, and porpoises) fall within this taxonomic branch, being most closely related to Hippopotamidae, hippopotamuses. Some modern taxonomists thus apply the name Cetartiodactyla () to this group, while others opt to include cetaceans within the existing name of Artiodactyla. Some researchers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquatic Mammal
Aquatic mammals and semiaquatic mammals are a diverse group of mammals that dwell partly or entirely in body of water, bodies of water. They include the various ''marine mammals'' who dwell in oceans, as well as various freshwater species, such as the European otter. They are not a taxon and are not unified by any distinct biological grouping, but rather their dependence on and integral relation to aquatic ecosystems. The level of dependence on aquatic life varies greatly among species. Among freshwater taxa, the Amazonian manatee and river dolphins are completely aquatic and fully dependent on aquatic ecosystems. Semiaquatic freshwater taxa include the Baikal seal, which feeds underwater but rests, molts, and breeds on land; and the capybara and hippopotamus which are able to venture in and out of water in search of food. Mammal adaptation to an aquatic lifestyle vary considerably between species. River dolphins and manatees are both fully aquatic and therefore are completely tet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infraorder
Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between Family_(biology), family and Class_(biology), class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. An immediately higher rank, superorder, is sometimes added directly above order, with suborder directly beneath order. An order can also be defined as a group of related families. What does and does not belong to each order is determined by a taxonomist, as is whether a particular order should be recognized at all. Often there is no exact agreement, with different taxonomists each taking a different position. There are no hard rules that a taxonomist needs to follow in describing or recognizing an order. Some taxa are accepted almost universally, while others are recognized only rarely. The name of an order is usually written with a capital letter. For some groups of organisms, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Monster
Sea monsters are beings from folklore believed to dwell in the sea and are often imagined to be of immense size. Marine monsters can take many forms, including sea dragons, sea serpents, or tentacled beasts. They can be slimy and scaly and are often pictured threatening ships or spouting jets of water. The definition of a "monster" is subjective; further, some sea monsters may have been based on scientifically accepted creatures, such as whales and types of giant squid, giant and colossal squid. Sightings and legends Sea monster accounts are found in virtually all cultures that have contact with the sea. For example, Avienius relates of Himilco the Navigator, Carthaginian explorer Himilco's voyage "...there monsters of the deep, and beasts swim amid the slow and sluggishly crawling ships." (lines 117–29 of ''Ora Maritima''). Humphrey Gilbert, Sir Humphrey Gilbert claimed to have encountered a lion-like monster with "glaring eyes" on his return voyage after formally claiming ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Largest Fish
Fish vary greatly in size. The extant whale shark and basking shark exceed all other fish by a considerable margin in weight and length. With the extinct Otodus megalodon exceeding all other fish extant and extinct (excluding tetrapods) in size. Fish in the common usage are a paraphyletic group that describes aquatic vertebrates while excluding the tetrapods, four limbed vertebrates nested within the lobe-finned fish, which include all land vertebrates and their nearest extinct relatives. This list therefore excludes the various marine reptiles and mammals, such as the extinct ichthyosaur, plesiosaur and mosasaur reptiles (none of which are dinosaurs) and the extant sirenia and cetacea mammals (such as the marine tetrapod blue whale, generally considered to be the largest animal known to have ever lived). Largest extant fish Jawless fish (Agnatha) * Hagfish ( Myxini) :The hagfish, which are not taxonomically true fish, are among the most primitive extant vertebrates. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cetus (mythology)
In Greek mythology, a Cetus () is a large sea monster. Perseus slew a cetus to save Andromeda from being sacrificed to it. Later, before the Trojan War, Heracles also killed one to rescue Hesione. The term cetacean (for whale) derives from ''cetus''. In Greek art, ''ceti'' were depicted as serpentine fish. The name of the mythological figure Ceto is derived from ''kētos''. The name of the constellation Cetus also derives from this word. Etymology In Ancient Greek ''ketos'' (, plural ''kete/ketea'', ), Latinized as ''cetus'' (pl. ''ceti'' or ''cete'' = ''cetea''), is any huge sea monster. Depictions A cetus was variously described as a sea monster or sea serpent. Other versions describe a cetus as a sea monster with the head of a wild boar or greyhound and the body of a whale or a dolphin with divided, fan-like tails. Ceti were said to be colossal beasts the size of a ship, their skulls alone measuring in length, their spines being a cubit in thickness, and their skeleto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
