WAcanthodii
WAdelophthalmidae
WAlethopteridaceae
WArchegosauroidea
WArcheriidae
WBauriinae
WBlastoid
WCallistophytaceaeWCallistophytales
WCladoselachidae
WCryptodontia
WCyathocrinitidae
WMedullosales
WEdrioasteroidea
WEmbolomeri
WEryopidaeWEryopoidea
WEurypterina
WEurypteroidea
WFenestellidae
WHelicoprion
WHibbertopteridaeWMedullosales
WMycteropoidea
WMycteroptidae
WNectrideaWMedullosales
WOrthoceratidae
WPetalodontidae
WPetalodontiformes
WPlatycrinitidae
WPylaecephalidae
WRhopalodontidae
WRostroconchia
WRubidgeinae
WStylonurina
WSyringoporidae
WTrigonotretidae
WWalchia
WWhaitsiidae
WZygopteridaceae