dorsal fin February 15, 2023 An unpaired fin located along the midline of the dorsal surface. It may have both spines and rays or just rays and consist of a single lobe, two lobes that are joined or separate, or a series of free spines and a lobe with rays. Related Articles: Glossary: adipose finGlossary: falcateGlossary: napeGlossary: predorsalGlossary: soft dorsal fin