Izinhlanzi yizilwane zasemanzini, i- craniate, i- gill- ezithwele izilwane ezingenazo izitho ezinamadijithi .Okufakiwe kule ncazelo ama- hagfish aphilayo, amalambu wezibani, nezinhlanzi ezigcwele uqwanga namathambo kanye namaqembu ahlobene ahlukahlukene asephelile.Cishe ama-99% ezinhlobo zezinhlanzi eziphilayo ziyizinhlanzi ezenziwe ngemisebe, ezingaphansi kwesigaba i-Actinopterygii, ezinamaphesenti angaphezu kwama-95% eqembu elincane le-teleost. I eziphilayo zokuqala ukuthi kungenziwa labizwa ngokuthi izinhlanzi babe othambile chordates ukuthi uqala ukuvela phakathi eCambria isikhathi. Yize babengenawo umgogodla weqiniso, babephethe ama- notochords ababavumela ukuthi basheshe beshesha ukwedlula ozakwabo abangenamgogodla. Izinhlanzi zizoqhubeka nokuguquguquka ngenkathi yePaleozoic, zihlukahluka zibe yizinhlobo ezahlukahlukene.Izinhlanzi eziningi zePaleozoic zakha izikhali zangaphandle ezazivikela ezilwaneni ezidla ezinye.Izinhlanzi zokuqala ezinemihlathi zavela esikhathini samaSilurian, okwathi ngemuva kwalokho abaningi ( njengoshaka ) baba yizilwane zasolwandle ezinamandla kunokuba nje isisulu se- arthropods . Iningi lezinhlanzi liyi- ectothermic ("igazi elinamakhaza"), livumela amazinga okushisa emizimba yabo ukuthi ehluke njengoba amazinga okushisa asendaweni eguqukayo, yize abanye babhukudi abakhulu abasebenza njengoshaka omhlophe ne- tuna bengabamba izinga lokushisa eliphakeme kakhulu. Izinhlanzi zingakwazi ukuxhumana ngomsindo, ikakhulukazi esimweni sokudla, ulaka noma ukuqomisana. Izinhlanzi zigcwele emanzini amaningi.