Protospongia

Protospongia hicksi is probably the only member of this genus of hexactinellid sponge to occur within the Burgess Shale and is rare in the Walcott Quarry where it represents about 0.24% of the community within the Greater Phyllopod bed (Caron and Jackson, 2008).^[12]

"Protospongia" rhenana Schlüter, 1892^[13] from the Lower Devonian (Emsian) Hunsrück Slate of Germany, had previously been included in the genus due to the architecture of its spicules resembling that of P. hicksi. Mehl (1996), however, has since transferred Schlüter's species to the genus Cyathophycus Walcott, 1879.^[14][15]

Burgess Shale fossils of P. hicksi consist entirely of fragments and isolated, cruciform spicules, so the living animal's average to maximum size and growth habitus cannot be determined. If those "Protospongia" fossils outside of the Burgess Shale are of or closely related to P. hicksi, then the growth habitus of various species would have been globular, such as P. tetranema, to cup-shaped, like Cyathophycus rhenana.

The generic homonym Protospongia Kent, 1880,^[16] is a nom. illeg. because taxonomically the type species, Protospongia haeckelii Kent, is now regarded as belonging to Proterospongia Kent, 1881^[17] Proterospongia is a genus of single-celled aquatic organisms which form colonies. It belongs to the choanoflagellate class and, interestingly, Choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of animals.

• Burgess Shale species 108