The inorganic content of pleromin in tooth plates of the living holocephalan, Chimaera phantasma, consists of a crystalline calcium phosphate known as beta-Ca3(PO4)2 (whitlockite).

The tooth plates in the living Holocephalan, Chimaera phantasma were studied by various techniques. They consisted of osteodentin and hypermineralized pleromin (kosmin). The degree of mineralization on the latter was as much as in the enameloid of Chondrichthyes and Osteichthyes. Scanning electron microscope observation indicated that the pleromin consisted of large and granular crystals. X-ray powder diffractometry, electron microprobe analysis and analytical electron microscopy revealed that the inorganic constituent of pleromin included, as an essential element, a beta-Ca3(PO4)2 (whitlockite) structure containing a small amount of Mg.