shark shark extant species shark family wide distribution atlantic pacific oceans species found outer continental shelf upper continental slope generally near evidence substantial upward movements caught deep uncommon japan common depths exhibiting primitive features shark termed living fossil reaches length dark brown like body dorsal pelvic anal fins placed far common comes fringed appearance pairs gill slits pair meeting throat seldom observed shark capture prey bending body forward like snake long extremely flexible jaws enable swallow prey rows small needle like teeth difficult prey escape feeds mainly cephalopods bony fishes sharks species viviparous embryos emerge egg inside mother survive primarily yolk gestation period long half years longest litter sizes vary distinct breeding season sharks occasional commercial fisheries little economic value assessed incidental catches population given low reproductive rate shark supposed giant relative suggested source reports sea taxonomy phylogeny shark scientifically recognized german visited japan brought specimens vienna manuscript describing species lost description shark authored american zoologist working metre female caught japan account extraordinary shark published volume placed new species genus family gave greek shark latin like common names species include shark shark shark silk shark early authors believed shark living representative long extinct groups sharks rays ancestors based multiple pointed teeth upper jaw directly eyes called like spinal column indistinct proposed allied obsolete taxonomic grouping containing forms era period contemporaries cope suggested instead related dominant sharks era cope went far assign species fossil genus recent investigations found similarities shark extinct groups shark exhibits number skeletal muscular traits firmly place modern sharks rays specifically cow sharks order proposed placed order shark belongs oldest extant shark dating late cretaceous possibly late ancient ancestry primitive characteristics shark members lineage described living fossil shark relatively recent species earliest known fossil teeth belonging species dating early pleistocene distribution habitat uncommon shark recorded number widely scattered locations atlantic pacific oceans eastern atlantic occurs northern norway northern scotland western ireland france morocco including central atlantic caught locations north azores southern brazil west_africa western atlantic reported waters new_england georgia western pacific known southeastern japan taiwan new_south_wales tasmania australia new_zealand central eastern pacific found hawaii california northern chile sharks southern africa described different species shark inhabits outer continental shelf upper middle continental slope favor productive areas caught depth usually occur deeper common depth august november temperature water layer exceeds sharks shift deeper water rare occasions species seen surface shark usually found close individual observed swimming area small sand dunes diet suggests substantial upward open water species vertical approaching surface night feed spatial segregation size reproductive condition description elongated like body strange appearance shark long likened mythical sea head broad flattened short rounded snout nostrils vertical slits separated openings leading skin moderately large eyes horizontally oval lack membranes protective long jaws positioned end snout opposed jaws sharks corners mouth devoid furrows tooth rows widely spaced numbering upper jaw lower jaw teeth number tooth small slender needle like alternating pairs long gill slits appearance created extended tips gill giving shark pair gill slits meet throat forming collar pectoral fins short rounded single small dorsal fin positioned far body opposite anal fin rounded margin pelvic anal fins large broad rounded positioned body caudal fin long roughly triangular lower lobe ventral notch upper lobe pair thick skin unknown function running belly separated groove relatively longer females males pelvic fins pushed closer anal fin dermal denticles small shaped like tip enlarged sharp dorsal margin caudal fin species uniform dark brown gray shark differs southern african relative having turns spiral valve versus proportional measurements longer head shorter gill slits maximum known length males females biology ecology highly specialized life deep sea shark reduced poorly skeleton enormous liver filled low density allowing maintain position water column little effort sharks open lateral line hair cells positioned grooves directly exposed surrounding configuration thought basal sharks enhance sensitivity minute movements prey sharks found tips tails missing probably predatory attacks shark species parasites identified shark include genus feeding long jaws shark highly extremely wide allowing swallow prey half size length jaws means deliver strong bite conventionally built sharks captured individuals found barely identifiable stomach contents suggesting fast rate long intervals species cephalopods bony fishes smaller sharks long individual caught found japanese squid comprise diet sharks includes slow moving deep dwelling types relatively large powerful swimmers open ocean ostensibly weak swimming shark captures active fast moving squid matter speculation possibility takes advantage injured squid exhausted dying spawning alternatively surprise prey curving body positioned fins launching quick strike forward manner snake able close gill slits create negative pressure suck prey mouth small sharp teeth shark similar squid easily body squid particularly rotated jaws observations captive sharks swimming mouths open suggest small teeth light dark mouth fool squid attacking life history shark viviparous developing embryos mainly yolk difference weight egg newborn indicates mother provides additional nutrition unknown means adult females functional functional right defined breeding season sex shark inhabits depths little seasonal influence possible mating male female sharks recorded litter size ranges average females eggs weeks yolk formation growth new eggs halt pregnancy apparently insufficient space inside body cavity newly eggs early stage embryos enclosed thin ellipsoid golden brown capsule embryo long head pointed seen jaws barely developed external gills begun appear fins present egg capsule shed embryo grows long expelled female body time embryo external gills fully developed size yolk sac remains constant length begins shrink completely disappearing length growth rate averages month entire gestation period half years far longer newborn sharks measure long males attain sexual maturity long females long human interactions shark seldom encountered alive poses danger humans scientists accidentally cut examining teeth august observation species natural habitat johnson sea link blake plateau southeastern united_states january japanese fisherman discovered long female alive surface illness weakness warm water brought died hours numerous authors advanced shark explanation sea sightings shark modest size existence giant relative particularly larger species known fossil record small numbers sharks caught incidentally commercial fisheries world particular regularly taken meant sea meant shrimp japanese fishermen regard damages nets shark sold meat processed economically significant low reproductive rate continuing expansion commercial fisheries habitat listed december caught metre shark fishing water kilometre deep near victoria australia shark taken identification confirmed
Frilled shark