Heteractinida is an extinct
grade of
Paleozoic (
Cambrian–
Permian)
sponges, sometimes used as a
class or
order. They are most commonly considered
paraphyletic with respect to
Calcarea (calcareous sponges),[1][2][3] though some studies instead argue that they are paraphyletic relative to
Hexactinellida (glass sponges).[4] Heteractinids can be distinguished by their six-pronged (snowflake-shaped)
spicules, whose symmetry historically suggested a relationship with the triradial calcarean sponges.[4]
The sponge-like Cambrian
Hetairacyathidae may be related to heteractinids,[5] though most instead consider hetairacyathids to be closer to
archaeocyaths and
radiocyaths.[6] 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.[7]
Family †
Wewokellidae King, 1943 [Mississippian–Permian]
References
^Pickett, J. (2002). "†Order Heteractinida Hinde, 1887". In Hooper, J.N.A.; Van Soest, R.W.M.; Willenz, P. (eds.). Systema Porifera: A Guide to the Classification of Sponges. Boston, MA:
Springer. pp. 1121–1140.
doi:
10.1007/978-1-4615-0747-5_117.
ISBN978-0-306-47260-2.