shark shark species shark extant member family specialized zone shark found worldwide tropical waters surface depth performs vertical migration staying depth day ascending shallower water night feed typically measuring length shark smallest living shark distinguished elongated cigar shaped body extremely large eyes relatively small fins active swimming predator bony fishes squid shrimp shark sizable liver allows maintain position water column minimal effort size structure eyes suggests adapted hunting night shark viviparous females typically giving birth litters meaning feed undeveloped eggs purpose mother small size shark poses little danger humans little commercial importance substantial numbers caught leading assessed species responsible damaging deep sea cables technology deployed taxonomy phylogeny english common shark derived japanese literally water refers sharp teeth habit snapping vigorously taken water common names species include japanese ragged tooth shark sand shark water shark described issue tokyo based long specimen found fish market japan type specimen long adult male found fish market taiwan genera family authors resurrected subgenus species placed family morphology shark suggests affinity shark shark sharks sharks recent phylogenetic analyses based mitochondrial dna suggested shark closely related shark sand sharks alternately analysis based suggests closest relatives shark sharks followed sharks teeth dating age found italy identical modern day shark description shark shaped body short head pointed snout eyes large lack membranes protective pairs gill slits long extending dorsal surface sizable arched jaws tip snout contain large teeth shaped like spikes knives sides fewer tooth rows jaw upper jaw large teeth separated lateral teeth row small intermediate teeth pectoral fins small broad rounded pelvic fins nearly large dorsal fin small low angular second dorsal fin smaller larger anal fin caudal fin moderately long upper lobe caudal slightly compressed weak lateral dermal denticles small flattened crown bearing small ridges backward pointing dark brown paler dark sides belly white corner mouth gill fins thin translucent white margins shark grows maximum length individuals long weigh distribution habitat shark distribution atlantic_ocean known brazil cape_verde guinea guinea south_africa reported northwestern atlantic indian_ocean occurs possibly pacific occurs japan taiwan northwest southward indonesia australia new_zealand eastward western coast americas baja california chile including marshall phoenix line hawaiian islands distribution records shark range bound latitudes average sea surface temperature species evenly distributed locally abundant certain areas suggesting strongly migratory shark usually found zone surface depth occasionally encountered near known strand beaches south_africa possibly stunned cold water biology ecology long body small fins large liver rich low density shark similar sharks shark liver comprise fifth shark weight acts float allows maintain neutral water column little effort like inhabitants zone shark apparently closer surface night feed descends deeper water day rarely found depth daytime large eyes shark equipped reflective green yellow lacking expanded iris suggest nocturnal hunter relies sight pick prey little known shark feeding habits thought active fast swimming predator based strong large tail behavior captured occasion shark south_africa jumped water pursuit bait diet consists small medium sized bony fishes including squid including shrimp sharks known preyed species shark viviparous typically gives birth litters pups gestation period unknown believed long embryos yolk long yolk sac fully absorbed mother produces large numbers thin walled egg contain eggs consumed embryos embryos yolk material quarter embryo total weight unclear shark manage share single sharks sand tiger shark survives pups born approximately long males attain maturity females defined reproductive season human interactions small size non cutting teeth oceanic habitat shark considered dangerous humans powerful bite invites caution species common fisheries meant largest numbers caught japanese fishery australian fishery operating indian_ocean species caught squid usually discarded small size low quality meat liver potentially valuable data available population status shark probably declining mortality coupled low reproductive rate led assessed installed deep sea cable september system suffered series shorts necessitated costly repairs discovered attacks shark responsible failures possibly attracted electric field cables sharks benthic nature presumably biting cables deployed problem solved protecting cables layer steel tape beneath dense coating
Crocodile shark