| Main Ref. | Reis, R.E. and E.H.L. Pereira, 1999 |
| Appearance refers to | |
| Bones in OsteoBase |
| Specialized organs | |
| Different appearance | |
| Different colors | |
| Remarks |
| Striking features | |
| Body shape lateral (shape guide) | elongated |
| Cross section | |
| Dorsal head profile | |
| Type of eyes | |
| Type of mouth/snout | |
| Position of mouth | |
| Type of scales | |
| Diagnosis |
Extreme reduction of dermal plates on the dorsal surface of body, with just the ventral and mid-ventral rows normally developed; absence of dorsal-fin spinelet and nuchal plate; absence of the connecting bone and ligament between second dorsal-fin proximal radial and rib of sixth centrum; reduction of lateral line; loss of the infraorbital sensory canal; and absence of adipose fin (versus present in all species but H. vestigipinnis). Fourth branched ray of pelvic fin longest, reaching to middle of anal fin when depressed. |
| Ease of Identification | easy to distinguish from other species. |
| Lateral Lines | Interrupted: No |
| Scales on lateral line | |
| Pored lateral line scales | |
| 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 | |
| on upper limb | |
| total | |
| Vertebrae | |
| preanal | |
| total |
| Attributes | |
| Fins number | 1 |
| Finlets No. | Dorsal 0 - 0 |
| Ventral 0 - 0 | |
| Spines total | |
| Soft-rays total | 8 - 8 |
| Adipose fin | absent |
| Attributes | more or less truncate; more or less normal |
| Fins number | |
| Spines total | |
| Soft-rays total | 4 - 5 |
| Pectoral | Attributes |
| Spines | |
| Soft-rays 6 - 6 | |
| Pelvics | Attributes other (see diagnosis) |
| Position thoracic before origin of D1 | |
| Spines | |
| Soft-rays 6 - 6 |