scientific called worms marine animals filter feed crown build upright tubes support protect soft bodies live oceans seas including excluding zone meters adult long wide largest long end body like swelling anchors animal tube enables body quickly threatened extended body little hairs sides draw food particles mouth inside slightly base unwanted material excluded closing lid mouth rejected switch reverse food moves stomach solid moved outside slightly blood vessel leads middle body stomach circular vessel base single blind vessel runs pair blood vessels near body wall lead downward ring stomach blind branches body heart major vessels contract waves blood water rely blood contains unusual small animals adaptation environments blood carries twice oxygen human weight filter body fluid returning useful products dumping remaining pair pores species builds colonies splitting sections reproduce sexually spring autumn eggs species form free swimming larvae feed days undergoes radical change minutes replaced adult moves outside changes gut upright bend stomach body species forms like larvae species known live year species live separately vertical tubes embedded soft sediment form masses buried rocks shells habitats populations reach tens thousand individuals square meter larvae familiar account significant proportion predators include fish tiny species predators parasites body digestive tract unknown significance humans listed species endangered body fossils good evidence created trace fossils found cretaceous periods possibly collectively called use feed 1940s 1990s family trees based morphological features placed sister group super includes minority adhere view researchers regard members super analysts molecular phylogeny confident members closely related non members relationships members unclear analyses regard sister groups place sub group comes names ancient egyptian goddess isis genera comparison similar description body structure adult long wide largest long skins cuticle rigid tubes similar material reinforced sediment particles debris species tubes erect horizontal tubes leave end body like swelling tube like structure anchors animal tube enables body threatened reducing body percent maximum length longitudinal muscles body quickly circular muscles slowly extend body internal fluid feeding end crown animal filter feeds small species crown simple circle medium size species bent shape outer inner sides largest species ends wind complex elaborate shapes increase area available feeding hollow held upright fluid pressure moved individually muscles mouth inside base crown gut runs mouth stomach runs stomach body exits outside little crown gut supported run length body connected body wall connects gut body divided compartments lined main body cavity crown called base share mouth hollow lid close mouth cavity called authors disagree fox barnes think built different process feeding circulation extended little hairs sides draw water base shorter inner sides flick food particles groove circle inside groove push particles mouth direct water current quickly maximize food catching area currents change diet includes algae small larvae unwanted material excluded closing lid mouth rejected switch reverse gut uses muscles food stomach digest food stomach majority food absorb building blocks proteins skins mainly summer solid moved outside slightly blood vessel starts membrane loosely stomach blind supplying stomach blood vessel leads middle body circular vessel base single blind vessel runs pair blood vessels near body wall lead downward ring species combined little ring downward vessel leads blind branches body heart muscles major vessels contract waves blood unlike animals live tubes water rely extends sediments blood containing unusual small animals adaptation environments blood carries oxygen blood volume body weight twice human walls blood vessels perform stage main fluid funnel like intake filter fluid second time returning useful products dumping remaining pair nervous system movement nervous center mouth nerve ring base ring supplies nerves skin body wall muscles nerve skin species trunk giant nerves transmit signals fast body danger threatens body tube limited slow movement partial emerging tube bending body extended food mouth reproduction naturally builds colonies splitting sections grow bodies experiments species split successfully parts reproductive tissue breed sexually spring autumn species male female reproductive organs cross eggs members separate sexes produced swollen stomach swim sperm exit captured individuals species species lay small eggs release water species larger eggs brood body tube stuck center eggs released feed develop larvae development eggs mixture characteristics early divisions egg cells divide completely radial gradually form stack circles process fate cell depends interaction cells rigid program cell experiments divided early embryos produced complete larvae formed originating formed embryo mouth like days sea bed days floor known species remaining species develop free swimming larvae feed upright cylinder fringed lobe hood connected patch outside apex hood pair smaller simpler adult mouth feeding mouth swimming days undergoes catastrophic radical change minutes hood absorbed adult created round mouth points upward gut develops bend outside finally adult builds tube live year ecology live oceans seas including arctic appear zone meters occur separately vertical tubes embedded soft sediment sand mud fine gravel form masses individuals buried rocks shells habitats populations reach tens thousand individuals square meter larvae familiar account significant proportion wall tube uses foundation building tube house unequal relationship experiences significant benefits harm benefits foundation tube food animals filter protection tube danger threatens tube predators known include fish tiny reaches square meter tidal flats california usa predators including fish crabs strongest section including exposed predators feed removed experiment effect reduced days broadly effective defenses appear unusual invertebrates inhabiting soft sediment important allowing reach high parasites unidentified digestive tract parasite unknown significance humans listed species endangered evolutionary history fossil record body fossils researching lower fossils interpreted shaped gut interpreted regarded synonyms genus opinion looked like found western canada specimens million years ago new fossil shells like authors opinion shaped gut extended line outside smaller shell attachment muscles close open shells animal length line needed longitudinal muscles cuticle protection suggest member stem group good evidence species created trace fossils found cretaceous periods animal bored algae tests shells shells tubes usually curved wide found possibly branching colonies family tree collectively called feed 1940s 1990s family trees based morphological features placed sister group super includes early development embryos form mouth form mouth nielsen views affiliated filter feed current driving cells cell regards multiple cell authors morphological analyses doubt disagree sub group worms suggests ancestral looks like mobile worm like colonial fact use feeding probably evolved independently adaptations lifestyle form disagreements form onwards analyses based molecular phylogeny compares features similarities dna placed super includes main super members include wrote true virtually morphology based phylogeny past century analyses molecular phylogeny confident members closely related non members relationships members unclear generally divided animals including animals larvae including molecular phylogeny indicates closely related closely related group despite similar feeding implies traditional definition recently term applied thinks change cause confusion analyses regard sister groups place sub group implying analysis concludes sub group teeth sister group sub groups authors suggest ancestors clade diverged probably taxonomy genera class order names given larvae usually called separate genus adults described described new species regards synonym thinks different species species diversity currently described larvae wrote undisputed adult species morphological types larvae identified
Phoronid