os actinostum

(plural ossa actinosta))

actinost (one of a series of endochondral bones in the pectoral and pelvic girdle on which the fin rays insert. Most teleosts lack or have greatly reduced pelvic actinosts. Teleosts have one row of actinosts between the fin rays and supporting skeleton (coracoid and scapula for the pectoral, basipterygia for the pelvic) while other fishes may have more rows, referred to as radials)