Submarine cement expecially important in reef edge and fore reef facies.

34 sponge species according to ref. 1683.
Collection data from Fagerstrom and Weidlich (1999)

Abstract ref. 1368:
The Permian Capitan reef was a predominantly heterotrophic ecosystem strongly differentiated into open surface and cryptic communities. Unlike modern phototrophic coralgal reefs, most of the preservable epibenthos was housed within the cryptos and zonation developed only in the shallow parts of the reef. Contrary to established opinion, most sphinctozoan sponges did not grow upright to form a baffling framework but rather were pendent cryptobionts, as were nodular bryozoans and rare solitary rugose corals and crinoids. Indeed, many members of the cryptos were obligate    cryptobionts. Much of the Middle Capitan reef framework was constructed by a scaffolding of large frondose    bryozoans, with the subsidiary platy sphinctozoan Guadalupia zitteliana. Bathymetrically shallow areas of both the Middle and Upper Capitan reef, however, were characterized by platy sponges. In parts of the Upper Capitan, some platy sponges (Gigantospongia discoforma) reached up to 2 m in diameter and formed the ceilings of huge cavities which supported an extensive cryptos. In the absence of destructive forces (both biotic and physical) prevalent on modern reefs, the relatively fragile Capitan reef remained intact after the death of the constructing organisms. Rigidity was imparted to this community by a postmortem encrustation of Tubiphytes and Archaeolithoporella, together with
microbial micrite. The resultant cavernous framework was partially infilled with sediment and preserved by
synsedimentary intergrowth of aragonitic botryoids and Archaeolithoporella. Extensive cement precipitation was
favoured by a number of factors including deep anoxia, which generated upwelling waters with elevated alkalinity.
Although the accumulation rate of the Capitan may have been comparable to that of modern coralgal reefs, both the trophic structure and relative contributions of inorganic and organic carbonate were profoundly different. 