anal fin

American  

noun

1. the median, unpaired fin on the ventral margin between the anus and the caudal fin in fishes.

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anal fin British  

noun

1. a median ventral unpaired fin, situated between the anus and the tail fin in fishes, that helps to maintain stable equilibrium

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Example Sentences

I drew a dorsal fin on top and an anal fin on the bottom, to prevent the shark from rolling side to side when it was moving forward.

From Literature

It has both pectoral and pelvic fins, which it uses to scurry clumsily along the ocean floor, and a "small fleshy anal fin" underneath its tail, like a propellor.

From The Verge

Tim Cwalinski, DNR Northern Lake Huron Fisheries Unit senior fisheries biologist, measured the fish, calling out the lengths to Unit Fisheries Technician Supervisor Pat Van Daele, collecting scales from panfish under 6 inches and dorsal or anal fin spines from larger predator fish.

From Washington Times

Anal fin resembling the second dorsal, greyish, with the margin dull-purple.

From Project Gutenberg

In the dorsal fin they have from 17 to 20 rays, and in the anal fin from 16 to 18; there are from 53 to 59 scales in the lateral line and 54 to 56 vertebrae in the vertebral column.

From Project Gutenberg