dorsal fin

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dorsal fin

[′dȯr·səl ′fin]
(vertebrate zoology)
A median longitudinal vertical fin on the dorsal aspect of a fish or other aquatic vertebrate.

dorsal fin

dorsal fin
An additional fin surface along the top of the fuselage just in front of the main fin. Dorsal fins help increase directional stability, especially at high air speeds and Mach numbers.
References in periodicals archive ?
octotaenia of the Red Sea, in having rounded dorsal, anal, and caudal fins, and lacking prolonged dorsal fin rays.
Diagnosis: Caudal fin emarginate, lobes not filamentous; caudal concavity 6-17% SL; dorsal fin rays 16; 3rd to 10th dorsal fin spines subequal; anal fin pointed, rays 7-8; 2nd to 4th rays elongated; pectoral fins rounded, rays 17-18, pelvic fins angular, reaching just past anus; lateral line scales 43-47; scale rows from 5th dorsal fin spine to lateral line 3 or 4; circumpeduncular scales 26-28; head with small auxiliary scales; proximal half of median fins scaly, but spinous dorsal fin naked.
Diagnosis: Caudal fin emarginate in male, lobe tips bluntly pointed; rear margin slightly concave or slightly forked in female, caudal concavity 7-12% SL; dorsal fin rays 15-17; interspinous membranes slightly incised; no elongated spines; rear end of fin pointed; anal fin rays 6-8; fin of male enlarged and pointed from elongated middle rays; pectoral fins pointed, rays 16-19, middle rays longest reaching vertical at anus; pelvic fins rounded, reaching anus.
Diagnosis: Caudal fin crescentic; 29-36% SL; caudal concavity 12-29% SL; dorsal fin rays 15-17, no elongated spines or rays, but interspinous membranes produced as short filament behind tip of each spine; anal fin rays 7 (one of 15 fish with 6 anal fin rays); pectoral fin pointed, reaching 3rd anal fin spine, rays 17-19; pelvic fin pointed.
Diagnosis: Male caudal fin lunate, with elongated lobes, outer rays filamentous; caudal concavity 19-35% SL; female caudal fin emarginate; dorsal fin rays 15-17, no elongated spines or rays, spinous and soft-rayed parts of equal height; anal fin rays 7-8; pectoral fins obtusely pointed, rays 18-20; pelvic fins pointed with slight elongation of 2nd and 3rd rays, reaching between anus and 3rd anal fin spine.
Dorsal fin rays 16-18; no elongated spines, but adults with rear end of fin pointed by elongation of 8th to 11th rays; longest ray twice length of longest spine.
Diagnosis: audal fin lunate; dorsal fin rays 16, rays longer than spines; anal fin pointed with 7 rays, third ray elongated; pectoral fin rays 17-18, reaching vertical at anus; pectoral and pelvic fins subequal; pelvic fin with 2nd ray slightly enlarged, filamentous, reaches anus.
Diagnosis: Caudal fin convex to truncate, or slightly concave; upper and lowermost rays slightly exserted; dorsal fin rays 16 or 17, third to 10th spines subequal; anal fin pointed in males, rounded in females, rays 7; pectoral fin slightly pointed, reaching vertical at anus, rays 18-20; pelvic fin pointed, 2th ray slightly elongated, reaching anus.
Diagnosis: Caudal fin deeply forked, lobes distinctly longer than head; lobe tips acute; caudal concavity 23-33% SL; dorsal fin rays 16 or 17, fin margin smooth and convex, inter-spinous membranes not incised; dorsal fin origin at vertical from rear edge of preopercle; anal fin rays 7; anal fin margin rounded; pectoral fins bluntly pointed, rays 19-20, middle rays longest, 3.
Diagnosis: Caudal fin asymmetric; dorsal fin rays 16, dorsal spines progressively longer with small cirrus from tip of each interspinous membrane; anal fin rays 7; pectoral fin rays 19-21; pelvic fins elongated with 2nd ray filamentous.
Dorsal fin rays X, 16; third spine pungent, slightly (4% SL) longer than fourth spine; dorsal fin spines 3, 4, and 5 with fleshy cirrus at tip; rear margin of fin pointed and elongate, with 9th to 14th rays elongated, reaching well past caudal fin base; 9th ray of holotype abnormally shortened, 8 mm compared to 27 mm for the 8th and 10th soft rays.