part of start stage end stage dorsal fin musculature muscle dorsal fin protractor protractor dorsalis Ceri zebrafish_anatomy ZFA:0005816 2014-10-27T12:59:02Z Anterior longitudinal muscles of the dorsal fin. The dorsal fin protractor originates from the base of the first soft ray of the dorsal fin, extends along the midline just underneath the skin, and inserts at the posterior portion of the skull. Contracting the dorsal protractor will raise the fin. unknown adult