Hexactinellid sponges are sponges with a skeleton made of four and/or six pointed silaceous spicules. Hexactinellids are relatively uncommon nowadays and are mostly found at substantial depths. They are often cup shaped animals with sturdy internal skeletons made up of fused spicules. They are fairly common relative to Demosponges as fossils, but this is thought to be at least in part because their spicules are sturdier than spongin and fossilize better. The earliest known hexactinellids are from the earliest Cambrian or late Neoproterozoic.
