Morphology Data of Gymnotus obscurus
Identification keys
Main Ref. Crampton, W.G.R., D.H. Thorsen and J.S. Albert, 2005
Appearance refers to
Bones in OsteoBase

Sex attributes

Specialized organs
Different appearance
Different colors

Descriptive characteristics of juvenile and adult

Striking features
Body shape lateral
Cross section
Dorsal head profile
Type of eyes
Type of mouth/snout
Position of mouth

Distinguished from its congeners endemic to the Amazon and Orinoco Basins and the Guyana Shield in having many pectoral-fin rays 20-22; and a color pattern of oblique and undivided thin pale bands, less than one-quarter width of dark bands, with straight high-contrast margins, which extend to the dorsal midline on the anterior half of the body, and of which many are interrupted at the ventral margin of the hypaxial muscles along the anterior two-thirds of the body. Differs further from congeners endemic to the Amazon-Orinoco basins and the Guyana Shield in having the following unique combination of characters: clear (unpigmented) patch at the caudal end of the anal-fin membrane in specimens 6.0-23.5 TL; and bands never divided to form band pairs (Ref. 55508).

Ease of Identification

Meristic characteristics of Gymnotus obscurus

Lateral Lines Interrupted: No
Scales on lateral line
Pored lateral line scales 108 - 132
Scales in lateral series
Scale rows above lateral line 5 - 7
Scale rows below lateral line
Scales around caudal peduncle
Gill clefts (sharks/rays only)
Gill rakers
on lower limb
on upper limb
preanal 35 - 37


Dorsal fin(s)

Fins number
Finlets No. Dorsal   
Spines total 0 - 0
Soft-rays total 0 - 0
Adipose fin absent

Caudal fin


Anal fin(s)

Fins number
Spines total
Soft-rays total 210 - 250

Paired fins

Pectoral Attributes  
Soft-rays   20 - 22
Pelvics Attributes  
Main Ref. (e.g. 9948)
Glossary ( e.g. cephalopods )
Entered by Torres, Armi G.
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cfm script by eagbayani, 17.10.00, php script by rolavides, 13/03/08 ,  last modified by sortiz, 06.27.17