Rigby, J. Keith Department of Geology, Brigham Young University, Provo, Utah.
Last reviewed:June 2019
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- Morphology and physiology
- Skeleton and spicules
- Fossil record
- Related Primary Literature
- Additional Reading
A class of sponges whose skeletons are made of siliceous hexactine spicules. Members of the class Hexactinellida (phylum Porifera) are commonly called glass sponges (Fig. 1). These exclusively marine sponges are widely distributed in modern oceans. The fossil record of hexactinellid sponges extends back to the late Precambrian. The basic spicule type of the class is a triaxial hexactine, in which the three pairs of opposed rays are at right angles to each other and lie along one of the three axes of a cube. Proximal ray ends and axial filaments meet at the center of the cube. These principal spicules and variants of that form make up the skeletons of the sponges. See also: Porifera; Precambrian; Silica minerals; Skeletal system
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