Heteractinida
The Heteractinids are a grade of sponges that are paraphyletic with respect to Hexactinellida. Their distinctive trait is their six-pronged spicules, whose symmetry historically suggested a relationship with the triradial Calcarean sponges. Nevertheless, they actually represent a polyphyletic grade, from which the hexactinellids arose.Families
The following families are placed in Heteractinida:
