| Main Ref. | Heemstra, P.C., 1986 |
| Appearance refers to | Male; Female |
| Bones in OsteoBase |
| Specialized organs | no special organs |
| Different appearance | males alike females |
| Different colors | males alike females |
| Remarks | Females are larger than males (Ref. 86435). |
| Striking features | striking shape of body |
| Body shape lateral | short and / or deep |
| Cross section | oval |
| 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 | terminal |
| Type of scales | scales embedded or partly/completely absent |
| Diagnosis |
The scaleless body is covered with extremely thick, elastic skin. The caudal fin is replaced by a rudder-like structure called 'clavus'. Dorsal and anal fins very high with short base; in swimming, these fins are flapped synchronously from side to side and can propel the fish at surprisingly good speed. Pectorals small and rounded, directed upward (Ref. 6885). Mouth very small; teeth fused to form a parrot-like beak. Gills 4, a slit behind the last; gill openings reduced to a small hole at the base of the pectoral fins. Gas bladder absent in adults. Description: Characterized further by deep and oval body, nearly circular, depth 1-1.5 in TL; rough texture of skin; clavus supported by about 12 fin rays, of which 8-9 bear ossicles (Ref. 90102). |
| Ease of Identification | easy to distinguish from other species. |
| Lateral Lines | Interrupted: No |
| Scales on lateral line | 0 - 0 |
| Pored lateral line scales | 0 - 0 |
| Scales in lateral series | 0 - 0 |
| Scale rows above lateral line | 0 - 0 |
| Scale rows below lateral line | 0 - 0 |
| Scales around caudal peduncle | 0 - 0 |
| Barbels | 0 |
| Gill clefts (sharks/rays only) | |
| Gill rakers | |
| on lower limb | |
| on upper limb | |
| total | |
| Vertebrae | |
| preanal | |
| total |
| Attributes | other |
| Fins number | 1 |
| Finlets No. | Dorsal 0 - 0 |
| Ventral 0 - 0 | |
| Spines total | 0 - 0 |
| Soft-rays total | 15 - 18 |
| Adipose fin | absent |
| Attributes | other (see remark) |
| Fins number | 1 |
| Spines total | 0 - 0 |
| Soft-rays total | 14 - 17 |
| Pectoral | Attributes other (see Diagnosis) |
| Spines 0 | |
| Soft-rays 12 - 13 | |
| Pelvics | Attributes suppressed/absent |
| Position absent | |
| Spines 0 | |
| Soft-rays 0 - 0 |