Heteractinida
Heteractinida is an extinct grade of Paleozoic sponges, sometimes used as a class or order. They are most commonly considered paraphyletic with respect to Calcarea, though some studies instead argue that they are paraphyletic relative to Hexactinellida. Heteractinids can be distinguished by their six-pronged spicules, whose symmetry historically suggested a relationship with the triradial calcarean sponges.
The sponge-like Cambrian Hetairacyathidae may be related to heteractinids, though most instead consider hetairacyathids to be closer to archaeocyaths. An example of a species in the Heteractinida class is the Gondekia lancifer; the Gondekia lancifer specimen is only the second articulated specimen known and is more complete than the holotype. It has an intact skeleton of felted sexiradiates of three orders of spicules.