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Tree of Life
Plant Flower, Tree
Invertebrate Octopus, Ant, Bee, Butterfly, Spider, Lobster
Vertebrate Fish, Seahorse, Ray, Shark, Frog, Turtle, Tortoise, Dinosaur
Bird, Ostrich, Owl, Crow, Parrot
Mammal Bat, Rabbit, Giraffe, Camel, Horse, Elephant, Mammoth
Whale, Dolphin, Walrus, Seal, Polar Bear, Bear, Cat, Tiger, Lion, Dog, Wolf
Monkey, Chimpanzee, Human
These are organized by a classification scheme developed exclusively for Cosma. More…
shark : any of numerous mostly marine cartilaginous fishes of medium to large size that have a fusiform body, lateral branchial clefts, and a tough usually dull gray skin roughened by minute tubercles and are typically active predators sometimes dangerous to humans — Webster
Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii) and are the sister group to the rays. However, the term “shark” has also been used for extinct members of the subclass Elasmobranchii outside the Selachimorpha, such as Cladoselache and Xenacanthus, as well as other Chondrichthyes such as the holocephalid eugenedontidans. Under this broader definition, the earliest known sharks date back to more than 420 million years ago. Acanthodians are often referred to as “spiny sharks”; though they are not part of Chondrichthyes proper, they are a paraphyletic assemblage leading to cartilaginous fish as a whole.
Since then, sharks have diversified into over 500 species. They range in size from the small dwarf lanternshark (Etmopterus perryi), a deep sea species of only 17 centimetres (6.7 in) in length, to the whale shark (Rhincodon typus), the largest fish in the world, which reaches approximately 12 metres (40 ft) in length. Sharks are found in all seas and are common to depths of 2,000 metres (6,600 ft). They generally do not live in freshwater although there are a few known exceptions, such as the bull shark and the river shark, which can survive and be found in both seawater and freshwater. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth.
Well-known species such as the great white shark, tiger shark, blue shark, mako shark, thresher shark, and the hammerhead shark are apex predators—organisms at the top of their underwater food chain. Many shark populations are threatened by human activities. — Wikipedia
10 Best Places to Swim With Sharks (Professional Association of Diving Instructors, Condé Nast Traveler)
25 Best Destinations for Sharks and Adventure (Travis Marshall, Scuba Diving)
Shark Diving Tips and Advice (Shart Trust)
10 Shark Diving Tips (Dive Magazine)
Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.
- Dinosaur-era sea lizard had teeth like a sharkon January 19, 2021 at 3:37 pm
New study identifies a bizarre new species suggesting that giant marine lizards thrived before the asteroid wiped them out 66 million years ago.
- New mangrove forest mapping tool puts...on January 15, 2021 at 2:10 pm
Mangroves are salt-tolerant plants found in intertidal areas throughout much of the world's tropical and subtropical coastlines. Mangrove ecosystems are highly variable, ranging from sparse, stunted shrubs to dense stands of thick-stemmed tall trees.
- 150-million-year-old shark was one of the largest...on January 14, 2021 at 2:32 pm
In a new study, an international research team led by Sebastian Stumpf from the University of Vienna describes an exceptionally well-preserved skeleton of the ancient shark Asteracanthus. This extremely rare fossil find comes from the famous Solnhofen limestones in Bavaria, which was formed in a tropical-subtropical lagoon landscape during the Late Jurassic, about 150 million years ago. The almost complete skeleton shows that Asteracanthus was two-and-a-half meters long in life, which makes […]
- Research reveals how teeth functioned and evolved...on January 13, 2021 at 10:00 am
A pioneering study by University of Bristol researchers finds that the evolution of teeth in the giant prehistoric shark Megalodon and its relatives was a by-product of becoming huge, rather than an adaptation to new feeding habits.
- High cost to wildlife from shark nets protecting...on January 13, 2021 at 9:05 am
"They're basically curtains of death," said shark diver Walter Bernardis as he reached over the side of his zodiac inflatable boat to pull up a net bobbing in eastern South Africa's subtropical waters.
- Future too warm for baby sharkson January 12, 2021 at 10:00 am
New research has found as climate change causes the world's oceans to warm, baby sharks are born smaller, exhausted, undernourished and into environments that are already difficult for them to survive in.
- Megalodons gave birth to large newborns that...on January 11, 2021 at 9:01 am
A new study shows that the gigantic Megalodon or megatooth shark, which lived nearly worldwide roughly 15-3.6 million years ago and reached at least 50 feet (15 meters) in length, gave birth to babies larger than most adult humans.
- For 50 years, biologist has studied bottlenose...on January 6, 2021 at 9:10 pm
Beginning his work in marine biology, Randy Wells thought he was a shark guy.
- Basking sharks travel in extended families with...on January 4, 2021 at 2:19 pm
Picture the scene. Swimming off Scotland's west coast during a summer holiday you notice a large dark shark nearly 10 meters long headed towards you. A prominent triangular dorsal fin cuts the surface, the powerful rhythmically beating tail driving it silently through the cloudy green depths. You're transfixed by a cavernous mouth large enough to swallow a seal.
- Young sea lion recovers from shark bite, returns...on December 30, 2020 at 7:26 am
A feisty young sea lion is back in the Northern California wild after five weeks of rehabilitation to treat a severe shark bite, domoic acid poisoning and malnutrition.