Portal:Cetáceos

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El portal de los cetáceos

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Los cetáceos (del latín cetus , « ballena » ; del griego antiguo κῆτος ( kêtos ), « pez enorme ,monstruo marino » ) son un infraorden de mamíferos acuáticos perteneciente al orden Artiodactyla que incluye a las ballenas , los delfines ylas marsopas . Sus características principales son su estilo de vida completamente acuático,su forma aerodinámica , su gran tamaño y su dieta exclusivamente carnívora . Se impulsan a través del agua con un poderoso movimiento hacia arriba y hacia abajo de su cola que termina en una aleta similar a un remo, utilizando sus extremidades anteriores en forma de aleta para maniobrar.

Si bien la mayoría de los cetáceos viven en ambientes marinos, un pequeño número reside únicamente en agua salobre o dulce . Al tener una distribución cosmopolita , se los puede encontrar en algunos ríos y en todos los océanos de la Tierra, y muchas especies habitan vastas áreas de distribución a las que migran con el cambio de estaciones.

Los cetáceos son famosos por su gran inteligencia , su comportamiento social complejo y el enorme tamaño de algunos de sus miembros. Por ejemplo, la ballena azul alcanza una longitud máxima confirmada de 29,9 metros y un peso de 173 toneladas, lo que la convierte en el animal más grande que se haya conocido.

Existen aproximadamente 89 especies vivientes divididas en dos parvórdenes : Odontoceti o ballenas dentadas (que incluyen marsopas , delfines , otras ballenas depredadoras como la beluga y el cachalote , y los poco comprendidos zifios ) y los Mysticeti o ballenas barbadas que se alimentan por filtración (que incluyen especies como la ballena azul , la ballena jorobada y la ballena de Groenlandia ). A pesar de sus cuerpos altamente modificados y su estilo de vida carnívoro, la evidencia genética y fósil ubica a los cetáceos dentro de los ungulados de dedos pares , más estrechamente relacionados con los hipopótamos dentro del clado Whippomorpha . ( Artículo completo... )

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Las entradas aquí consisten en artículos buenos y destacados , que cumplen con un conjunto básico de altos estándares editoriales.

Image 1

La falsa orca ( Pseudorca crassidens ) es una especie de delfín oceánico que es el único representante existente del género Pseudorca . Se encuentra en océanos de todo el mundo, pero principalmente en regiones tropicales. Fue descrita por primera vez en 1846 como una especie de marsopa basándose en un cráneo, que fue revisado cuando se observaron los primeros cadáveres en 1861. El nombre "falsa orca" proviene de tener un cráneo similar al de la orca ( Orcinus orca ), u orca.

La falsa orca alcanza una longitud máxima de 6 m (20 pies), aunque el tamaño puede variar en todo el mundo. Es muy sociable, se sabe que forma grupos de hasta 50 miembros, y también puede formar grupos con otras especies de delfines, como el delfín mular común ( Tursiops truncatus ). Puede formar vínculos estrechos con otras especies, así como tener interacciones sexuales con ellas. Pero también se sabe que la falsa orca se alimenta de otros delfines, aunque normalmente come calamares y peces. Es un buceador de grandes profundidades; la profundidad máxima conocida es de 927,5 m (3043 pies); la velocidad máxima es de ~ 29 km/h (18 mph). ( Artículo completo... )
Image 2

Holotype skull of A. deinodon

Acrophyseter is a genus of extinct sperm whale that lived in the Late Miocene off the coast of what is now Peru. The genus comprises two species: A. deinodon and A. robustus. It is part of a group of macroraptorial sperm whales that all share several features for hunting large prey, such as deeply rooted and thick teeth. Acrophyseter measured 4–4.5 metres (13–15 ft) in length, making it the smallest macroraptorial sperm whale currently known. Because of its short pointed snout and strongly curved front teeth, it probably fed on the large marine vertebrates of its time, such as seals and other whales. (Full article...)
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Southern right whale

Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and porpoises. Dolphins and porpoises may be considered whales from a formal, cladistic perspective. Whales, dolphins and porpoises belong to the order Cetartiodactyla, which consists of even-toed ungulates. Their closest non-cetacean living relatives are the hippopotamuses, from which they and other cetaceans diverged about 54 million years ago. The two parvorders of whales, baleen whales (Mysticeti) and toothed whales (Odontoceti), are thought to have had their last common ancestor around 34 million years ago. Mysticetes include four extant (living) families: Balaenopteridae (the rorquals), Balaenidae (right whales), Cetotheriidae (the pygmy right whale), and Eschrichtiidae (the grey whale). Odontocetes include the Monodontidae (belugas and narwhals), Physeteridae (the sperm whale), Kogiidae (the dwarf and pygmy sperm whale), and Ziphiidae (the beaked whales), as well as the six families of dolphins and porpoises which are not considered whales in the informal sense.

Whales are fully aquatic, open-ocean animals: they can feed, mate, give birth, suckle and raise their young at sea. Whales range in size from the 2.6 metres (8.5 ft) and 135 kilograms (298 lb) dwarf sperm whale to the 29.9 metres (98 ft) and 190 tonnes (210 short tons) blue whale, which is the largest known animal that has ever lived. The sperm whale is the largest toothed predator on Earth. Several whale species exhibit sexual dimorphism, in that the females are larger than males. (Full article...)
Image 4
Cetacea is an infraorder that comprises the 94 species of whales, dolphins, and porpoises. It is divided into toothed whales (Odontoceti) and baleen whales (Mysticeti), which diverged from each other in the Eocene some 50 million years ago (mya). Cetaceans are descended from land-dwelling hoofed mammals, and the now extinct archaeocetes represent the several transitional phases from terrestrial to completely aquatic. Historically, cetaceans were thought to have descended from the wolf-like mesonychians, but cladistic analyses confirm their placement with even-toed ungulates in the order Cetartiodactyla.

Whale populations were drastically reduced in the 20th century from intensive whaling, which lead to a moratorium on hunting by the International Whaling Commission in 1982. Smaller cetaceans are at risk of accidentally getting caught by fishing vessels using, namely, seine fishing, drift netting, or gill netting operations. (Full article...)
Image 5

The holotype and only specimen

Orcinus meyeri is a fossil species of Orcinus (killer whales) found in the Early Miocene deposits of southern Germany, known from two jaw fragments and 18 isolated teeth. It was originally described as Delphinus acutidens in 1859, but reclassified in 1873. Its validity is disputed, and it may be a synonymous with the ancient sperm whale Physeterula dubusi. It was found in the Alpine town of Stockach in the Molasse basin, which was a coastal area with strong tidal currents. (Full article...)
Image 6

Pilot whales are cetaceans belonging to the genus Globicephala. The two extant species are the long-finned pilot whale (G. melas) and the short-finned pilot whale (G. macrorhynchus). The two are not readily distinguishable at sea, and analysis of the skulls is the best way to distinguish between the species. Between the two species, they range nearly worldwide, with long-finned pilot whales living in colder waters and short-finned pilot whales living in tropical and subtropical waters. Pilot whales are among the largest of the oceanic dolphins, exceeded in size only by the orca. They and other large members of the dolphin family are also known as blackfish.

Pilot whales feed primarily on squid, but will also hunt large demersal fish such as cod and turbot. They are highly social and may remain with their birth pod throughout their lifetime. Short-finned pilot whales are one of the few non-primate mammal species in which females go through menopause, and postreproductive females continue to contribute to their pod. Pilot whales are notorious for stranding themselves on beaches, but the reason behind this is not fully understood, although marine biologists have shed light on the discovery it is due to the mammals inner ear (their principal navigational sonar) being damaged from noise pollution in the ocean, such as from cargo ships or military exercises. The conservation status of short-finned and long-finned pilot whales has been determined to be least concern. (Full article...)
Image 7

The sperm whale or cachalot (Physeter macrocephalus) is the largest of the toothed whales and the largest toothed predator. It is the only living member of the genus Physeter and one of three extant species in the sperm whale family, along with the pygmy sperm whale and dwarf sperm whale of the genus Kogia.

The sperm whale is a pelagic mammal with a worldwide range, and will migrate seasonally for feeding and breeding. Females and young males live together in groups, while mature males (bulls) live solitary lives outside of the mating season. The females cooperate to protect and nurse their young. Females give birth every four to twenty years, and care for the calves for more than a decade. A mature, healthy sperm whale has no natural predators, although calves and weakened adults are sometimes killed by pods of killer whales (orcas). (Full article...)
Image 8

The narwhal (Monodon monoceros) is a species of toothed whale native to the Arctic. It is the only member of the genus Monodon and one of two living representatives of the family Monodontidae. The narwhal has a similar build to the closely related beluga whale, with which it overlaps in range and can interbreed. It is a stocky cetacean with a relatively blunt snout, a large melon, and a shallow ridge in place of a dorsal fin. Males of this species have a large 1.5–3.0 m (4 ft 11 in – 9 ft 10 in) long tusk, which is a left protruded canine thought to serve as a weapon or as a tool for feeding, attracting mates or sensing water salinity. Specially adapted slow-twitch muscles, along with the jointed neck vertebrae and shallow dorsal ridge allow for easy movement through the Arctic environment, where the narwhal spends extended periods at great depths.

The narwhal inhabits the Arctic waters of Canada, Greenland and Russia. Every year, it migrates to ice-free summering grounds, usually in shallow waters, and often returns to the same sites in subsequent years. Its diet mainly consists of polar and Arctic cod, Greenland halibut, cuttlefish, shrimp, and armhook squid. Plunging at depths of up to 2,370 m (7,780 ft), the narwhal is among the deepest-diving cetaceans. It travels in groups of three to eight, with aggregations of up to 1,000 occurring in the summer months. It mates in the offshore pack ice from March to May, and the young are born in July or August of the following year. When communicating, a variety of clicks, whistles and knocks are used. (Full article...)
Image 9

Cast of skull at the Natural History Museum of the University of Pisa

Livyatan is an extinct genus of macroraptorial sperm whale containing one known species: L. melvillei. The genus name was inspired by the biblical sea monster Leviathan, and the species name by Herman Melville, the author of the famous novel Moby-Dick about a white bull sperm whale. Herman Melville often referred to whales as "Leviathans" in his book. It is mainly known from the Pisco Formation of Peru during the Tortonian stage of the Miocene epoch, about 9.9–8.9 million years ago (mya); however, finds of isolated teeth from other locations such as Chile, Argentina, the United States (California), South Africa and Australia imply that either it or a close relative survived into the Pliocene, around 5 mya, and may have had a global presence. It was a member of a group of macroraptorial sperm whales (or "raptorial sperm whales") and was probably an apex predator, preying on whales, seals and so forth. Characteristically of raptorial sperm whales, Livyatan had functional, enamel-coated teeth on the upper and lower jaws, as well as several features suitable for hunting large prey.

Livyatan's total length has been estimated to be about 13.5–17.5 m (44–57 ft), almost similar to that of the modern sperm whale (Physeter macrocephalus), making it one of the largest predators known to have existed. The teeth of Livyatan measured 36.2 cm (1.19 ft), and are the largest biting teeth of any known animal, excluding tusks. It is distinguished from the other raptorial sperm whales by the basin on the skull spanning the length of the snout. The spermaceti organ contained in that basin is thought to have been used in echolocation and communication, or for ramming prey and other sperm whales. The whale may have interacted with the large extinct shark megalodon (Otodus megalodon), competing with it for a similar food source. Its extinction was probably caused by a cooling event at the end of the Miocene period causing a reduction in food populations. The geological formation where the whale has been found has also preserved a large assemblage of marine life, such as sharks and marine mammals. (Full article...)
Image 10

Restored skeleton

Brygmophyseter, known as the biting sperm whale, is an extinct genus of toothed whale in the sperm whale family with one species, B. shigensis. When it was first described in 1994, the species was placed in the genus Scaldicetus based on tooth morphology, but this was later revised in 1995. In 2006, it was classified into the genus Naganocetus, which is considered to be a junior synonym. The only known specimen, a nearly complete skeleton, was dated to be around 16–15 million years old (middle Miocene). Brygmophyseter is thought to have been 6.5–7 meters (21–23 ft) long, and it probably had 11 or 12 teeth in the upper and lower jaws. Brygmophyseter is part of a group of macroraptorial sperm whales (often shortened to "raptorial") which tended to be apex predators using their large teeth to catch struggling prey such as whales. It had a spermaceti organ which was probably used for biosonar like in the modern sperm whale. The whale has made an appearance on The History Channel's TV series Jurassic Fight Club. (Full article...)
Image 11
The anatomist John Struthers (at left, in top hat) with the Tay Whale at John Woods's yard, Dundee, 1884, photographed by George Washington Wilson

The Tay Whale, known locally as the Monster, was a humpback whale that swam into the Firth of Tay of eastern Scotland in 1883. It was harpooned in a hunt, but escaped, and was found floating dead off Stonehaven a week later. It was towed into Dundee by a showman, John Woods, and exhibited on a train tour of Scotland and England.

The Regius Professor of Anatomy at Aberdeen University, John Struthers dissected the whale, much of the time in public with a military band playing in the background, organised by Woods. The decomposing whale made Woods a great deal of money, and Struthers famous. (Full article...)
Image 12

Artistic reconstruction

Arktocara is an extinct genus of river dolphin from the Oligocene epoch of Alaska, containing one species, A. yakataga. Having been discovered in 25-million-year-old strata near the 60th parallel north, it is perhaps the oldest-known crown toothed whale and the northmost river dolphin discovered. It was a member of the now-extinct family Allodelphinidae, along with the genera Allodelphis, Goedertius, Ninjadelphis, and Zarhinocetus. It measured approximately 2.26 or 2.28 meters (7.4 or 7.5 ft), comparable to its closest living relative, the South Asian river dolphin, which measures 2.4 meters (7.9 ft). However, the animal probably had an elongated beak and neck, so it may have been longer. The animal is known only from a partially preserved skull. Its ecology may have been similar to the modern-day Dall's porpoise, and it may have competed with contemporaneous delphinoids. Its remains were found in the Poul Creek Formation, which has also yielded several mollusk species. (Full article...)
Image 13

Skull of Janjucetus hunderi at the Melbourne Museum

Janjucetus is an extinct genus of cetacean, and a basal baleen whale (Mysticeti), from the Late Oligocene around 25 million years ago (mya) off south-east Australia, containing one species J. hunderi. Unlike modern mysticetes, it possessed large teeth for gripping and shredding prey, and lacked baleen, and so was likely to have been a predator that captured large single prey animals rather than filter feeding. However, its teeth may have interlocked, much like those of the modern-day filter-feeding crabeater seal (Lobodon carcinophaga), which would have allowed some filter-feeding behaviour. Its hunting behaviour was probably similar to the modern-day leopard seal (Hydrurga leptonyx), probably eating large fish. Like baleen whales, Janjucetus could not echolocate; however, it did have unusually large eyes, and so probably had an acute sense of vision. The only specimen was found on the Jan Juc beach, where the remains of the extinct whales Mammalodon, Prosqualodon and Waipatia have also been discovered. (Full article...)
Image 14
Species of the infraorder Cetacea

The evolution of cetaceans is thought to have begun in the Indian subcontinent from even-toed ungulates (Artiodactyla) 50 million years ago (mya) and to have proceeded over a period of at least 15 million years. Cetaceans are fully aquatic mammals belonging to the order Artiodactyla and branched off from other artiodactyls around 50 mya. Cetaceans are thought to have evolved during the Eocene (56-34 mya), the second epoch of the present-extending Cenozoic Era. Molecular and morphological analyses suggest Cetacea share a relatively recent closest common ancestor with hippopotami and that they are sister groups. Being mammals, they surface to breathe air; they have five finger bones (even-toed) in their fins; they nurse their young; and, despite their fully aquatic life style, they retain many skeletal features from their terrestrial ancestors. Research conducted in the late 1970s in Pakistan revealed several stages in the transition of cetaceans from land to sea.

The two modern parvorders of cetaceans – Mysticeti (baleen whales) and Odontoceti (toothed whales) – are thought to have separated from each other around 28–33 mya in a second cetacean radiation, the first occurring with the archaeocetes. The adaptation of animal echolocation in toothed whales distinguishes them from fully aquatic archaeocetes and early baleen whales. The presence of baleen in baleen whales occurred gradually, with earlier varieties having very little baleen, and their size is linked to baleen dependence (and subsequent increase in filter feeding). (Full article...)
Image 15
Orca's Song is a 1987 picturebook written by Anne Cameron and illustrated in black and white by Nelle Olsen. Published by Harbour Publishing, the book is an adaptation of a Pacific Northwest Indigenous story. Orca's Song is a pourquoi story about a black orca who falls in love with an osprey; the two mate to create a baby orca with the black and white patterning found on the whales.

While some reviewers appreciated the art and text of the story, it received criticism from Indigenous authors and scholars who disputed Cameron's claim of sole authorship and copyright for the story. Consequently, reprints of the book began to attribute the storyteller Klopinum for the story's inspiration although Cameron retained sole authorship credit and copyright. The story has also been noted as an early example of a lesbian relationship (between Orca and Osprey) in picturebook literature and one of the few such picturebooks published before 2000 to lack a moralising tone. (Full article...)

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Crédito de la foto: Bronwen Lea, 14 de mayo de 2004.

Un esqueleto de ballena azul , afuera del Laboratorio Marino Long en la Universidad de California, Santa Cruz .

Las ballenas azules son los animales más grandes que han existido jamás. La caza de ballenas azules ha provocado una grave disminución de su población en todo el mundo.

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¿Sabías que...?

...el canto de las ballenas jorobadas se produce cuando fuerzan el aire a través de sus enormes cavidades nasales .

... las barbas de las bocas de las ballenas Místicas se usaban para endurecer partes de los trajes y vestidos de las mujeres, como los corsés.

...el cachalote debe su nombre a la sustancia blanca lechosa llamada espermaceti que se encontró en su cabeza y que originalmente se confundió con esperma .

...la grasa de la leche de la ballena beluga es tan alta que la cría gana hasta dos kilos por día con la dieta. Es tan grasosa que el color es verde.

...la ballena azul tiene el pene más grande de cualquier animal en la Tierra, estimado en más de 2 m (más de 6½ pies)

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Imágenes generales -cargar nuevo lote

Las siguientes son imágenes de varios artículos relacionados con los cetáceos en Wikipedia.

Image 1Anatomía del delfín mular (de Ballena dentada )
Image 2El corazón de una ballena azul con una persona parada a su lado.
Image 3Delfín de flancos blancos del Atlántico capturado en una cacería en Hvalba, en las Islas Feroe, y retirado con una carretilla elevadora (de Ballena dentada )
Image 4Fósil de Squalodon (de ballena dentada )
Image 5Biosonar de cetáceos (de ballena dentada )
Image 6Posibles relaciones entre los cetáceos y otros grupos de ungulados. (de Evolución de los cetáceos )
Image 7Los arqueocetos (como este Basilosaurus ) tenían una dentición heterodonta (de Evolución de los cetáceos )
Image 8Ilustración de ballena jorobada
Image 9Los delfines ( mamíferos acuáticos ) y los ictiosaurios ( reptiles marinos extintos ) comparten una serie de adaptaciones únicas para un estilo de vida completamente acuático y se utilizan con frecuencia como ejemplos extremos de evolución convergente (de Evolución de los cetáceos ).
Image 10Las ballenas barbadas varían considerablemente en tamaño y forma, dependiendo de su comportamiento alimentario. (de Ballena barbada )
Image 11El esqueleto de una ballena de Groenlandia con la estructura ósea de las extremidades traseras y la pelvis marcadas en rojo. Esta estructura ósea permanece interna durante toda la vida de la especie. (de Evolution of ketoceans )
Image 12Los restos de una ballena franca del Atlántico Norte tras chocar con la hélice de un barco
Image 13Ilustración de ballena gris
Image 14Ilustración de ballena minke común
Image 15Los Archaeomysticetes, como Janjucetus , tenían dientes.
Image 16Gráfica de la población mundial de ballenas azules
Image 17Protesta contra la caza científica de ballenas por parte de Japón
Image 18Ilustración de ballena azul
Image 19Orca cazando una foca de Weddell (de Ballena dentada )
Image 20Una orca llamada Ulises actuando en SeaWorld, 2009 (de Toothed whale )
Image 21Ilustración de ballena de aleta
Image 22Piojos de ballena naranja en una ballena franca
Image 23Especies del infraorden Cetacea (de Evolución de los cetáceos )
Image 24Ilustración de ballena sei
Image 25Ilustración de la ballena franca del Atlántico sur
Image 26La nariz de la ballena está llena de una sustancia cerosa que se usaba ampliamente en velas, lámparas de aceite y lubricantes (de Ballena dentada )
Image 27Ilustración de ballena minke antártica
Image 28Caza científica japonesa de una pareja de ballenas minke antárticas (de ballena barbada )
Image 29Ilustración de ballena franca pigmea
Image 30Ballena franca hembra con cría
Image 31Espectrograma de vocalizaciones de delfines. Los silbidos, gemidos y chasquidos son visibles como V invertidas, estrías horizontales y líneas verticales, respectivamente. (de Ballena dentada )
Image 32Cráneo de Acrophyseter (de Evolución de los cetáceos )
Image 33Ballenas jorobadas se alimentan mientras pescan con redes de burbujas
Image 34Una ballena como la representó Conrad Gessner , 1587, en su Historiae animalium (de Ballena dentada )
Image 35El megalodón cazaba ballenas barbadas del Mioceno (de Ballena barbada )
Image 36Ilustración de ballena de Groenlandia
Image 37Restauración de Janjucetus hunderi (de ballena barbada )
Image 38Características del esqueleto de un cachalote (de Ballena dentada )
Image 39Sus ojos son relativamente pequeños para su tamaño.
Image 40Las placas accesorias de las barbas se estrechan hasta formar pequeños pelos (de la ballena barbada )
Image 41Ilustración de la ballena del Edén
Image 42Ilustración de la ballena franca del Atlántico Norte
Image 43Esqueleto de Pakicetus attocki (de Evolución de los cetáceos )
Image 44Esqueleto de ballena jorobada. Observe cómo la mandíbula está dividida en dos.
Image 45Rorcual de Bryde (de ballena barbada )
Image 46Delfines de lados blancos del Pacífico nadando con delfines (de Ballena dentada )
Image 47Diagrama que ilustra la generación, propagación y recepción de sonido en una ballena dentada. Los sonidos salientes son rojos y los entrantes son verdes (de la ballena dentada )
Image 48Un árbol filogenético que muestra las relaciones entre las familias de cetáceos. (de Evolución de los cetáceos )