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Order Summary for Gymnotiformes
Main Ref.:	Nelson, J.S., 1994
Order:	Gymnotiformes    knifefishes
Class:	Actinopterygii (ray-finned fishes)
Sister Order:	Siluriformes     150 M years
Ref.:	Carroll, R., 1988     Colbert, E. and M. Morales, 1991
First fossil record:	late Jurassic
Occurs in:	Marine      Freshwater      Brackish
Remarks:	Body eel-like (compressed or rounded); pelvic girdle and fins absent; dorsal fin absent; anal fin extremely long (more than 140 rays and extending from near pectoral fin origin to near tip of body) and employed in forward and backward movements; caudal fin absent or greatly reduced; restricted gill openings; anal opening under head or pectorals; basal pterygiophores to anal fin with only one section (radial) and a hemispherical cartilaginous head that articulates the fin rays (allowing them to move in a circular motion); electric organs present; suboperculum absent; palatine not ossified; maxilla rudimentary.
Class etymology:	Greek aktis = ray, thunderbolt, beam + Greek pterygion, diminutive of pteryx = wing, fin. Ref. 45335.
Order etymology:	Greek, gymnos = naked + Latin, forma = shape (Ref. 45335); ous or otos refers to opercle.
Families:	6 Apteronotidae , Gymnotidae , Hypopomidae , Rhamphichthyidae , Sternopygidae

Identification keys | Tree of Life

Ref.:   ( e.g. 9948)
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Page created by: Eli, 17.10.00, last modified by Eli, 15.02.05.