A new species of the genus Tetragonopterus is described from specimens of the upper and middle portions of the rio Tocantins drainage. The new species can be distinguished from all congeners by the possession of a very uniquely shaped maxilla.
Ichthyofauna; Neotropical; Systematics; Taxonomy
| Holotype | n | Paratypes Mean SD | ||||
|---|---|---|---|---|---|---|
| Standard Length (mm) | 37.7 | 30 | 26.6 | - 37.7 | 33.2 | - |
| Percentages of Standard Length | ||||||
| Depth at dorsal-fin origin | 34.9 | 30 | 28.6 | - 36.6 | 33.1 | 2.1 |
| Snout to dorsal-fin origin | 49.3 | 30 | 38.4 | - 54.3 | 50.5 | 2.6 |
| Snout to pectoral-fin origin | 25.9 | 30 | 25.1 | - 28.5 | 26.9 | 0.9 |
| Snout to pelvic-fin origin | 45.8 | 30 | 44.1 | - 49.0 | 46.4 | 1.3 |
| Snout to anal-fin origin | 59.7 | 30 | 58.6 | - 63.7 | 61.3 | 1.4 |
| Caudal-peduncle depth | 11.0 | 30 | 9.4 | - 11.6 | 10.6 | 0.6 |
| Caudal-peduncle length | 10.8 | 30 | 8.0 | - 12.8 | 10.9 | 1.1 |
| Pectoral-fin length | 22.9 | 30 | 20.8 | - 24.7 | 22.2 | 1.1 |
| Pelvic-fin length | ||||||
| Males | 22.5 | 11 | 18.8 | - 23.8 | 21.7 | 1.6 |
| Females/immatures | - | 16 | 15.8 | - 20.3 | 18.0 | 1.0 |
| Pelvic-fin origin to anal-fin origin | 16.5 | 30 | 14.3 | - 18.5 | 16.3 | 1.0 |
| Dorsal-fin length | ||||||
| Males | 44.9 | 11 | 31.6 | - 44.9 | 35.6 | 3.7 |
| Females/immatures | - | 16 | 28.1 | - 32.9 | 30.3 | 1.2 |
| Dorsal-fin base length | 14.7 | 30 | 12.5 | - 16.1 | 14.4 | 0.9 |
| Anal-fin length | ||||||
| Males | 27.3 | 11 | 23.1 | - 27.3 | 25.3 | 1.9 |
| Females/immatures | - | 16 | 19.5 | - 24.4 | 22.3 | 1.1 |
| Anal-fin base length | 33.4 | 30 | 29.0 | - 33.5 | 31.3 | 1.4 |
| Eye to dorsal-fin origin | 37.2 | 30 | 35.5 | - 48.9 | 37.7 | 2.4 |
| Dorsal-fin origin to caudal-fin base | 52.8 | 30 | 48.3 | - 54.5 | 51.6 | 1.5 |
| Head depth | 27.2 | 30 | 23.5 | - 30.4 | 26.5 | 1.4 |
| Head length | 23.7 | 30 | 23.7 | - 26.7 | 25.0 | 0.8 |
| Percentages of Head Length | ||||||
| Horizontal eye diameter | 42.8 | 30 | 23.0 | - 50.1 | 44.1 | 5.7 |
| Snout length | 26.1 | 30 | 21.7 | - 33.5 | 25.5 | 2.0 |
| Interorbital width | 35.3 | 30 | 31.4 | - 36.8 | 33.6 | 1.4 |
| Upper jaw length | 44.6 | 30 | 43.1 | - 50.1 | 46.3 | 1.7 |
