Stromatoporoidea

Stromatoporoidea is an extinct clade of sea sponges common in the fossil record from the Middle Ordovician to the Late Devonian. They can be characterized by their densely layered calcite skeletons lacking spicules. Stromatoporoids were among the most abundant and important reef-builders of their time, living close together in flat biostromes or elevated bioherms on soft tropical carbonate platforms.

Externally, some species have raised bumps (mamelons) and star-shaped crevices (astrorhizae), which together help vent exhalant water away from the living surface. Internally, stromatoporoids have a mesh-like skeletal system combining extensive horizontal layers (laminae), vertical rods (pillars), and boxy spaces (galleries), along with other features. The most common growth forms range from laminar (flattened) to domical (dome-shaped). Spheroidal, finger-like, or tree-like species also occur, though they are rare in most environments.