Heteractinid, hexactinellid and sphaeroclonid sponges as rare components of anthaspidellid-dominated reefs from the Ordovician of the Precordillera, western Argentina

Three new sponges have been discovered in the extensively studied reef mounds of the Lower Ordovician limestones of the Precordillera of western Argentina significantly increasing the diversity of the group in this region.These groups occur as solitary individuals and are unusual in reef ecosystems at this time.The sponges include a new species, Niquivilispongia asteria gen.et sp.nov., which is the second named heteractinid from Argentina, fragments of a reticulosan (?Mattaspongia sp.), and a sphaeroclone demosponge.These include sponge groups that are relatively common in Mesozoic reef settings, but rare in Ordovician reefs.This shows that a consortium of sponges was evolving to adapt to reef environments during the earlier part of the Ordovician, including some that only appear as rare components of the ecosystem.Those rare components were either adapted to specific but limited niches within the reef system, or were opportunistic colonizers from other habitats.