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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.
Pacific marine national monuments do not harm...
on February 20, 2020 at 3:52 pm
New scientific findings released today in the peer-reviewed journal Nature Communications, show that expansion Aof the Pacific Remote Islands and Papahanaumokuakea marine national monuments did not cause overall economic harm to the Hawaii-based longline tuna fishing fleet.
Shark may avoid cold blood by holding its breath...
on February 20, 2020 at 2:21 pm
Scalloped hammerhead sharks stay warm as they descend into cold, deep water off the coast of Hawaii, suggesting the cold-blooded species may maintain its body temperature on dives by holding its breath, according to new research presented at the Ocean Sciences Meeting 2020 in San Diego, California.
Caribbean sharks in need of large marine...
on February 14, 2020 at 8:06 am
Governments must provide larger spatial protections in the Greater Caribbean for threatened, highly migratory species such as sharks, is the call from a diverse group of marine scientists including Stony Brook University School of Marine and Atmospheric Sciences (SoMAS) Ph.D. Candidate, Oliver Shipley, and led by the conservation NGO Beneath the Waves in a letter to published in Science.
Boom and bust for ancient sea dragons
on February 13, 2020 at 2:35 pm
A new study by scientists from the University of Bristol's School of Earth Sciences, shows a well-known group of extinct marine reptiles had an early burst in their diversity and evolution—but that a failure to adapt in the long-run may have led to their extinction.
Mediterranean great white sharks found to have...
on February 11, 2020 at 11:00 pm
The great white shark has been in the Mediterranean for 3.2 million years, way longer than researchers have hypothesized until now. The white sharks currently living in the Mediterranean are genetically closer to those of the Pacific Ocean than to their neighbors inhabiting the Atlantic.
Cluster of sharks in one spot off Carolinas coast...
on February 11, 2020 at 3:27 pm
The clustering of great white sharks off the Carolinas coast is growing more pronounced and mysterious, based on satellite tracking data shared Saturday on social media.
Updated shark tagging atlas provides more than 50...
on February 3, 2020 at 3:52 pm
A 52-year database of the distribution and movements of 35 Atlantic shark species revealed new information on some of the least known species. It also uncovered a few surprises about where sharks go and how long they live.
Family matters for world's second biggest fish
on February 3, 2020 at 3:16 pm
The world's second biggest fish—the basking shark—prefers to travel with family to familiar feeding sites, according to a new study led by the University of Aberdeen.
Recreational fishers catching more sharks and rays
on January 27, 2020 at 8:44 pm
Recreational fishers are increasingly targeting sharks and rays, a situation that is causing concern among researchers.
Revenge of the albatross: seabirds expose illicit...
on January 27, 2020 at 8:00 pm
For the magnificent but maligned albatross, it was time for a little payback after centuries of insult and injury.