An unpaired fin located on the underside of a fish posterior to the anus.
- ‘Dorsal and anal fins are typically completely formed by the time the fish has reached 7-13 mm.’
- ‘The fleshy, stalk-like pectoral and pelvic fins and similar fleshy second dorsal and anal fins are also unlike any other marine fishes.’
- ‘The siganids have many strong spines with venom glands in dorsal and anal fins that contain a painful toxin.’
- ‘The second dorsal and the anal fin are well-separated from the caudal fin.’
- ‘The dorsal and anal fins, which push the fish along, are way off the central axis of its body, yet the animal swims a straight path without rocking up and down.’