dorsal fin

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dorsal fin

n.
One of one or more unpaired fins on the back of fishes and certain marine mammals.

dorsal fin

any unpaired median fin on the backs of fishes and some other aquatic vertebrates. The fin maintains balance during locomotion.
References in periodicals archive ?
The present analysis also found differences in the mean numbers of dorsal fin rays, trunk rings and tail rings, as well as trunk and tail subdorsal rings, although the ranges of these counts always overlapped, in some cases greatly, between the two nominal taxa.
Description: Dorsal fin rays IX, 11; anal fin rays 111,9; pectoral fin rays (including upper rudimentary ray) 14; pored lateral line scales 16 + 9 (one paratype with 15 + 6, and another with 16 + 7); scales above lateral line to origin of dorsal fin 2; scales below lateral line to origin of anal fin 6; median predorsal scales 5 (4-5); median preventral scales 6 (one paratype with 5); rows of scales on cheek 2; circumpeduncular scales 15 (15-16); gill rakers 13 (two paratypes with 14); pseudobranchs 13 (12-13).
Diagnosis: Caudal fin deeply forked, lobes attenuate, filamentous, particularly in males; caudal concavity 23-32% SL; dorsal fin rays 16-18; dorsal fin origin anterior to upper end of gill opening; male with 2nd and 3rd dorsal fin spines elongated, flexible, with small fleshy tab at tip; 3rd dorsal fin spine elongated in adult female, rear end of fin rounded; anal fin angular, rays 7-8, 3rd to 5th rays elongated; pectoral fins rounded, rays 19-21, uppermost 1 or 2 rays unbranched; pelvic fins pointed.
Measurements are expressed as times in standard length: gill rakers on first gill arch 6+9=15 (6+10=16); pored scales in lateral line scale row 23 (23); median predorsal scales 17 (18); circumferential scales (in front of pelvic fins) 13 (13); circumpeduncular scales 13 (13); peduncular scales (from base of last anal fin ray to end of hypural plate) 9 (9); dorsal fin rays 20 (20); anal fin rays 27 (28); pectoral fin rays 7 (7); pelvic fin rays 5 (5); and caudal fin rays i7+7i (i8+8i); head 3.
Diagnosis: Dorsal fin rays 10 or 11; anal fin rays 9-11; pectoral rays 17-19; small spinules on head and body except for snout, posterior caudal peduncle and base of fins; snout length 4.
Abbreviations in the table: SL = Standard length, BD = Depth at pelvic fins, PD = Predorsal length, PA = Preanal length, PP = Prepelvic length, CPL = Caudal peduncle length, CPD = Caudal peduncle depth, HL = Head length, SL = Snout length, ED = Eye diameter, D = number of dorsal fin rays, A = number of anal fin rays, LL = scales on lateral series.
Counts for dorsal fin rays (X or XI,21-23), anal fin rays (II,18-20), pectoral fin rays (15-17), gill rakers on the first branchial arch (4-6 + 11-12), pored lateral line scales (95-106), scales in lateral series (115-130), predorsal scales (33-40) and preopercle serrae (29-44) were generally similar and overlapping.
Dorsal fin rays with small melanophores (sometimes forming very thin continuous dark streak) along anterior and posterior margins of branched and unbranched portions, dorsal fin interradial margins otherwise without melanophores.