A report on Fin and Cetacea

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Fins are used by aquatic animals, such as this orca, to generate thrust and control the subsequent motion
Dolphin anatomy
Caudal fin of a great white shark
Humpback whale fluke
Aquatic animals typically use fins for locomotion
(1) pectoral fins (paired), (2) pelvic fins (paired), (3) dorsal fin, (4) adipose fin, (5) anal fin, (6) caudal (tail) fin
Biosonar
Comparison between A) the swimming fin of a lobe-finned fish and B) the walking leg of a tetrapod. Bones considered to correspond with each other have the same color.
Bubble net feeding
In a parallel but independent evolution, the ancient reptile Ichthyosaurus communis developed fins (or flippers) very similar to fish (or dolphins)
Killer whale porpoising
In the 1990s the CIA built a robotic catfish called Charlie to test the feasibility of unmanned underwater vehicles
Two views of the skeletons of Dorudon atrox, extinct for 40 million years, and Maiacetus inuus, extinct for 47.5 million years, in the swimming position for comparison.
Cetaceans display convergent evolution with fish and aquatic reptiles
Fossil of a Maiacetus (red, beige skull) with fetus (blue, red teeth) shortly before the end of gestation
Whales caught 2010–2014, by country
Dominoes made of baleen
A whale as depicted by Conrad Gesner, 1587, in Historiae animalium
"Destruction of Leviathan" engraving by Gustave Doré, 1865
Silver coin with Tarus riding a dolphin
Constellation Cetus
Depiction of baleen whaling, 1840
Stranded sperm whale engraving, 1598
Sea World show featuring bottlenose dolphins and false killer whales
Ulises the orca, 2009
Dawn Brancheau doing a show four years before the incident
SeaWorld pilot whale with trainers

Fish, and other aquatic animals such as cetaceans, actively propel and steer themselves with pectoral and tail fins.

- Fin

The fluke is set horizontally on the body, unlike fish, which have vertical tails.

- Cetacea
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2 related topics with Alpha

Overall

Dorsal fin of a shark

Dorsal fin

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Dorsal fin of a shark
Most fish, like this Prussian carp, have one dorsal fin
Sharks typically have two dorsal fins
The yellowfin tuna also has two dorsal fins
Haddocks have three dorsal fins
Differences of dorsal fins of orcas between male and female
The dorsal fin of a white shark contains dermal fibers that work "like riggings that stabilize a ship's mast", and stiffen dynamically as the shark swims faster to control roll and yaw.<ref>Lingham‐Soliar T (2005) "Dorsal fin in the white shark, Carcharodon carcharias: A dynamic stabilizer for fast swimming" Journal of Morphology, 263 (1): 1–11. {{doi|10.1002/jmor.10207}} pdf{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
Large retractable dorsal fin of the Indo-Pacific sailfish
Various species of Ichthyosaurs displaying different types of dorsal fins
Dorsal fin of a perch showing the basals and radials of the pterygiophore that support the dorsal fin.
Closeup of the dorsal fin of a common dragonet

A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom.

Many species of animals possessing dorsal fins are not particularly closely related to each other, though through convergent evolution they have independently evolved external superficial fish-like body plans adapted to their marine environments, including most numerously fish, but also mammals such as cetaceans (whales, dolphins, and porpoises), and even extinct ancient marine reptiles such as various known species of ichthyosaurs.

Pinniped

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Restoration of Puijila
Fossil of Enaliarctos
Fossil skull cast of Piscophoca sp. from Phocidae
Reconstruction of Archaeodobenus akamatsui family Odobenidae
Male and female South American sea lions, showing sexual dimorphism
Light reflection on an elephant seal eye
Frontal view of brown fur seal head
Vibrissae of walrus
Weddell seal underwater
Northern elephant seal resting in water
Walrus on ice off Alaska. This species has a discontinuous distribution around the Arctic Circle.
Harbor seal hauled out on rock
Steller sea lion with white sturgeon
Leopard seal capturing emperor penguin
Orca hunting a Weddell seal
Walrus herd on ice floe
Northern fur seal breeding colony
Male northern elephant seals fighting for dominance and females
Harp seal mother nursing pup
Adult Antarctic fur seal with pups
Walrus males are known to use vocalizations to attract mates.
Sea lion balancing a ball
Inuit seal sculptures at the Linden Museum
Captive sea lion at Kobe Oji Zoo Kobe, Japan
Men killing northern fur seals on Saint Paul Island, Alaska, in the mid-1890s
Protests of Canada's seal hunts
Grey seal on beach occupied by humans near Niechorze, Poland. Pinnipeds and humans may compete for space and resources.

Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals in the clade Pinnipedia.

Pinnipeds tend to be slower swimmers than cetaceans, typically cruising at 5 – compared to around 20 kn for several species of dolphin.