species ray family member genus despite appearance closely related true family species ranges generally waters deeper found buried sand mud near beds reaching length heart shaped pectoral fin disc long robust tail bearing positioned dorsal fins developed caudal fin distinctive traits plain colored ray parallel rows large hooked start middle run tail encountered singly groups feeds small benthic invertebrates bony fishes viviparous developing young drawing yolk sac females birth pups annually late summer following roughly year long gestation period listed concern majority range lies united_states waters common commercial value heavily commercially status species mexican waters known taxonomy phylogeny scientifically described american issue scientific journal assigned genus named latin series row reference rows year later journal placed species newly created genus type specimen adult male caught february common names species include shark confused australian sharks california round ray based morphology determined phylogenetic study form basal clade order sister group members order encompassing relatives finding affirmed closely related true family possibility long considered description pectoral fin disc heart shaped slightly longer wide thick snout short broad blunt tip protruding slightly disc eyes small widely spaced larger eyes lie closely wide nostrils preceded moderately large broad flaps skin mouth wide gently arched pair running mouth corners nostrils roughly area lower lip inscribed deep mouth corners small teeth low crowns sharp blunt arranged rows upper jaw rows lower jaw pairs gill slits small located beneath disc pelvic fins curved outer margins angular rear tips males long tail robust longer disc lateral skin running dorsal fins similar size shape longer tall rounded posterior margins dorsal fin lies closer caudal fin pelvic fins caudal fin developed elliptical distinct lower lobe skin entirely covered tiny dermal denticles additionally large rows leading margin disc small groups snout tip eyes shoulders rows running middle second dorsal fin species plain olive grayish brown white snout disc margins barely translucent grows long distribution habitat endemic northeastern pacific_ocean found additional isolated populations reportedly abundant coastal waters california baja california uncommon north dwelling nature species typically found close shore water recorded deep inhabits coastal habitats muddy sandy bottoms including bays beaches found beds adjacent areas biology ecology day spends time partially buried sediment encountered singly small groups large form particular bays diet ray consists worms crustaceans including crabs small bony fishes including detect prey sensitive electric fields frequency turn preyed sharks northern elephant seal known parasites species include mate late summer females birth following year time peaking august viviparous developing embryos sustained birth yolk females bear litters pups year newborn rays measure long males females reach sexual maturity long respectively human interactions harmless readily approached underwater public united_states ray common faces substantial threats occasionally caught incidentally commercial recreational economic value range lies waters species assessed concern overall mexican waters population small fragmented degree affected fishing uncertain iucn listed locally noting fisheries shrimp urgent need additional information ensure long term regional survival
Thornback guitarfish