shark called cigar shark species small shark family shark occurs warm oceanic waters worldwide particularly near islands recorded deep vertically day approaching surface dusk descending dawn reaching length shark long cylindrical body short blunt snout large eyes tiny dorsal fins large caudal fin dark brown light covering underside dark collar throat gill slits shark refers feeding habit round cut cutter larger animals marks sharks found wide variety marine mammals fishes submarines cables human bodies smaller prey squid sharks adaptations water column likely rely stealth capture active prey dark collar mimic silhouette small fish rest body blends light ventral predator approaches lure shark lips specialized flesh like set lower teeth species known travel schools rarely encountered oceanic habitat handful documented attacks humans apparently caused sharks shark regarded highly dangerous listed shark concern widely distributed commercial value particularly susceptible fisheries taxonomy french originally described shark voyage corvette giving type specimen caught brazil account published voyage sur les volume report voyage american coined new genus species isis egyptian goddess light earliest accounts wounds left shark animals ancient legend held entering leave pieces flesh sacrifice community chief later centuries explanations wounds advanced including bacteria parasites predecessor discovered cigar shark generally known responsible shark expert popularized shark species originally called demon whale common names shark include shark shark smooth shark description shark elongated cigar shaped body short rounded snout nostrils short skin large oval green eyes placed forward head extensive vision eyes large positioned upper surface head mouth short forming nearly transverse line surrounded enlarged lips tooth rows upper jaw tooth rows lower jaw increasing body size upper lower teeth extremely different upper teeth small narrow upright tapering single smooth edged lower teeth smooth edged larger broader knife like bases form single saw like cutting edge pairs gill slits small pectoral fins short roughly shape dorsal fins placed far body originating ahead pelvic fins second located second dorsal fin slightly larger pelvic fins larger anal fin absent caudal fin broad lower lobe large upper prominent ventral notch dermal denticles flattened slight central raised corners shark chocolate brown color subtly lighter dark collar gill region fins translucent margins caudal fin darker margin complex light producing organs called densely cover entire underside collar produce vivid green glow maximum recorded length species males females distribution habitat inhabiting world major tropical warm temperate oceanic basins shark common latitudes surface water temperature atlantic reported bahamas southern brazil west cape_verde guinea southern south_africa east south caught mauritius new_guinea australia new_zealand including tasmania lord howe island japan central eastern pacific occurs fiji north east easter fresh wounds observed marine mammals suggest shark range far california warm years based catch records shark appears conduct vertical migration way spends day depth night rises upper water column usually remaining rare occasions surface species tolerant low dissolved oxygen levels sharks related genera frequently found near islands reproductive purposes hold congregations large prey animals northeastern atlantic adults found smallest largest individuals found lower higher latitudes respectively evidence gender segregation biology ecology best known biting neat round tissue marine mammals large fish shark considered wholly smaller prey wide strong bite virtue heavily small fins weak muscles ambush predator spends time water column maintain neutral liver comprise weight rich low density species higher skeletal density body cavity liver larger oil content higher large caudal fin allows quick burst speed catch larger faster prey come range shark regularly replaces teeth like sharks sheds lower teeth entire rows time shark long calculated shed sets lower teeth time long totaling teeth represents significant investment resources probably shark old sets teeth calcium content unlike sharks shark cells concentrated concentric area horizontal streak visual field help focus prey shark fat shark known travel schools increase effectiveness lure discourage larger predators green shark strongest known shark reported persist hours taken water positioned serve disrupt silhouette matching light strategy known counter illumination common organisms zone individual set denticles small naked eye suggesting evolved fool animals high visual close distances set apart glowing underside darker collar sides throat serve lure mimicking silhouette small fish appeal lure multiplied school sharks collar function way shark known case absence light attracts prey serve prevent premature detection incoming predators shark match limited range light vertical movements likely serve preserve effectiveness disguise times day weather conditions feeding virtually type medium large sized oceanic animal sharing habitat shark open attack bite found including sperm including fur seals leopard seals elephant seals sharks including blue sharks sharks sharks great white sharks sharks sand tiger sharks including bony fishes including shark regularly hunts eats entire squid mantle length comparable size shark prey modest dimensions parasitic attacks shark leave round crater wound averaging deep prevalence attacks high hawaii nearly adult spinner bears species weakened animals appear susceptible western atlantic records beached headed dozens hundreds recent healing shark wounds wounds rare beached impact prey species terms resources diverted growth reproduction uncertain shark exhibits number mouth parasitic lifestyle shark body surface prey closing tongue create pressure lower surroundings lips ensure tight seal bites narrow upper teeth anchors razor sharp lower teeth prey finally shark twists body complete circular cut possibly aided initial forward momentum subsequent struggles prey action lower teeth assisted forth vibrations jaw mechanism akin electric carving knife shark ability create strong mouth likely utility capturing smaller prey squid life history like sharks shark viviparous developing embryos sustained yolk birth females functional birth litters pups record female carrying embryos long close birth size developed yolk suggesting slow rate yolk absorption long gestation period embryos developed brown dark collar differentiated newborn sharks measure long males attain sexual maturity length females length human interactions favoring offshore waters seldom encountered humans shark considered dangerous small size implicated attacks notable case school fierce long fish blunt attacked underwater photographer open ocean dive similar reports come survivors suffering small clean deep bites night time march resident shark swimming channel records bodies recovered water post shark bites 1970s submarines forced base repair damage caused shark bites boots caused sound oil inside leak impaired navigation unknown enemy weapon initially feared shark identified culprit problem solved installing covers 1980s thirty submarines damaged shark bites rubber electric cable leading sounding probe ensure safety shipping zones solution apply coating equipment telecommunications cables damaged species harm inflicted sharks fishing nets economically important species minor negative effect commercial fisheries shark small value taken nets lack significant population threats coupled worldwide distribution led iucn assess shark concern
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