†family Petalaxidae Fomichev 1953 (horn coral)
Parent taxon: Stauriida according to E. W. Bamber and J. Fedorowski 1998
Sister taxa: Arachnophyllina, Aulophyllina, Calostylina, Caniniina, Columnariina, Cyathophyllina, Diffingiina, Hillia, Ketophyllina, Kleopatrinidae, Lithostrotionina, Lomaphyllum, Lonsdaleiina, Lophophyllidiidae, Lophotichiidae, Lycophyllina, Metriophyllina, Mictocystoides, Petraphyllidae, Plerophyllina, Ptenophyllina, Stauriina, Stereolasmatina, Streptelasmatina, Yatsengiidae
Subtaxa: Antheria, Cystolonsdaleia, Huanglongophyllum, Ivanovia, Lithostrotionella, Lytvophyllum, Omaniphyllum, Paralithostrotion, Petalaxis, Protoivanovia
Ecology: stationary epifaunal suspension feeder