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The first shark-like chondrichthyans appeared in the oceans 400 million years ago, [1] developing into the crown group of sharks by the Early Jurassic. [2] Listed below are extant species of shark. Sharks are spread across 512 described and 23 undescribed species in eight orders. The families and genera within the orders are listed in ...
Orthacanthus platypternus from the Craddock Bonebed shark layer in Texas, USA, shows evidence of resorption, and the equivalent of an "enamel pearl." [8] Some of the teeth specimens found at this location show evidence of resorption, which has not been previously observed in other faunal members at the same location. [8]
The use of sight probably varies with species and water conditions. The shark's field of vision can swap between monocular and stereoscopic at any time. [58] A micro-spectrophotometry study of 17 species of sharks found 10 had only rod photoreceptors and no cone cells in their retinas giving them good night vision while making them colorblind.
"They are also considered a keystone species, meaning they are integral to the ecology they inhabit." ... Great white sharks have been observed in Texas waters since the 1950s, as recorded in the ...
In a milestone decision in 2013, CITES prohibited international trade in the fins of the scalloped hammerhead (pictured) and four other shark species. [5] Shark species are increasingly becoming threatened because of commercial and recreational fishing pressures, the impact of non-shark fisheries on the seabed and shark prey species, and other ...
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The 125,000 (470,000 L) exhibit includes nurse sharks, amberjack, Atlantic tarpon, grouper, a barracuda, and many other species that could be found in a naturally occurring habitat in the Gulf of Mexico. The exhibit formerly hosted an iconic sand tiger shark (Hans) but a mishap in 2015 led to the death of Hans as well as about 400 other fish. [7]
In this screen capture, Jill Horner a recent transplant to the area from Buffalo, N.Y., captured video of a shark swimming off Hilton Head Island on Sept. 4, 2022, Labor Day weekend.