†Petalaxis Milne-Edwards and Haime 1852 (horn coral)
Anthozoa - Stauriida - Petalaxidae
Synonym: Grootia Yu 1984
Parent taxon: Petalaxidae according to J. Fedorowski et al. 2007
Sister taxa: Antheria, Cystolonsdaleia, Huanglongophyllum, Ivanovia, Lithostrotionella, Lytvophyllum, Omaniphyllum, Paralithostrotion, Protoivanovia
Subtaxa: Petalaxis allisonae, Petalaxis baculatus, Petalaxis beauchampi, Petalaxis besti, Petalaxis branisai, Petalaxis crassicolumnus, Petalaxis ellesmerensis, Petalaxis elyensis, Petalaxis exiguus, Petalaxis mokomokensis, Petalaxis multilamellatus, Petalaxis occidentalis, Petalaxis parvus, Petalaxis sutherlandi, Petalaxis thorsteinssoni
Ecology: stationary epifaunal suspension feeder