Definition of Term

pectoral fin

(English) The paired fin born by the pectoral girdle, usually just behind the gill opening or slightly dorsal or ventral to this position. Also called omopterygium or homopterygium. This fin is generally larger than the pelvic fin and less variable in position and structure. The pectoral is low on the body in more primitive bony fishes and higher in more advanced ones. It functions to steer, brake and propel the fish. Pectoral fin ray counts include all the rays branched and unbranched. The length is measured from the origin (upper or outer part of base) to the distal tip of the fin. Abbreviated as P or P1.

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