| Main Ref. | Kukuev, E.I., 1998 |
| Appearance refers to | |
| Bones in OsteoBase |
| Specialized organs | |
| Different appearance | |
| Different colors | |
| Remarks |
| Striking features | none |
| Body shape lateral | eel-like |
| Cross section | compressed |
| Dorsal head profile | more or less straight |
| Type of eyes | more or less normal |
| Type of mouth/snout | more or less normal |
| Position of mouth | superior |
| Type of scales | |
| Diagnosis |
Dark brownish, silvery ventrally; paired fins and caudal fin uniformly black. Body extremely elongate. Large adults with a pair of dermal keels midlaterally on each side. Small, flexible projection at tip of lower jaw. Gill membranes joined forward, below anterior edge of eye, and free from isthmus. No rayed dorsal fin. No scales (Ref. 43939). In adults, head depth 29-33% of lower jaw length. Postorbital area 8.1-9.7% SL or 34.4-38.8% (less than 3 times smaller than HL). Rear edge of gill cover overlaps with the vertical of the 5th vertebrae. Postadipose distance 7-8% SL (Ref. 31260). |
| Ease of Identification |
| Lateral Lines | Interrupted: No |
| Scales on lateral line | |
| Pored lateral line scales | 75 - 83 |
| Scales in lateral series | |
| Scale rows above lateral line | |
| Scale rows below lateral line | |
| Scales around caudal peduncle | |
| Barbels | |
| Gill clefts (sharks/rays only) | |
| Gill rakers | |
| on lower limb | 0 - 0 |
| on upper limb | 0 - 0 |
| total | 0 - 0 |
| Vertebrae | |
| preanal | |
| total | 78 - 80 |
| Attributes | greatly reduced or absent |
| Fins number | |
| Finlets No. | Dorsal 0 - 0 |
| Ventral 0 - 0 | |
| Spines total | 0 - 0 |
| Soft-rays total | 0 - 0 |
| Adipose fin | present |
| Attributes | forked; more or less normal |
| Fins number | 1 |
| Spines total | 0 - 0 |
| Soft-rays total | 14 - 17 |
| Pectoral | Attributes more or less normal |
| Spines 0 | |
| Soft-rays 13 - 16 | |
| Pelvics | Attributes more or less normal |
| Position abdominal before origin of D1 | |
| Spines 0 | |
| Soft-rays 9 - 10 |