Phosphatic Biomineralization in Scyphozoa (Cnidaria): A Review

Phosphatic biomineralization is unknown in modern species of Scyphozoa (Cnidaria). However, some extinct groups of Scyphozoa, such as conulariids and Sphenothallus, were capable of secreting phosphatic exoskeletons. Both conulariids and Sphenothallus used apatite to improve the mechanical properties of their skeletons, which offered better protection than the non-biomineralized periderms. The skeletons of conulariids and Sphenothallus have a lamellar microstructure. The shell lamellae of conulariids are often pierced by tiny pores. Several apatitic mineral structures have been described in conulariids and Sphenothallus, including plywood-like structures. Different lattice parameters of the apatite indicate that the biomineralization mechanisms of the phosphatic cnidarians Sphenothallus and conulariids differed from each other.