Autapomorphies of Tetragonopterus argenteus:

1. Laterosensory canal of sixth infraorbital (76): (0> 1) branched. Reversal of synapomorphy 2 of node 203. Paralleled in Markiana nigripinnis, Odontostilbe microcephala, Oligosarcus cf. jenynsii .

2. Length of caudal-fin canal of lateral line (93): (0> 1) almost reaching posterior margin of caudal fin. Paralleled in nodes 177 and 216 and in Astyanax pelegrini .

3. Tubules for passage of blood vessels on lamellar portion of maxilla (98): (0> 1) tubule with anterior branch running parallel to anterior margin of maxilla and reaching one third of its length. Paralleled in node 201.

4. Ethmopalatine cartilage (171): (0> 1) present and conspicuous. Paralleled in Charax stenopterus and Phenacogaster tegatus .

5. Base of second pectoral ray (231): (1> 0) large and partially overlapping base of first pectoral ray from medial view. Paralleled in nodes 164 and 301 and in Moenkhausia dichroura and Prionobrama paraguayensis .

6. Anterior margin of scales (318): (0> 1) with conspicuous undulations. Paralleled in Markiana nigripinnis .

7. Radii of scales (322): (0> 1) converging at focus. Reversal of synapomorphy 7 of the Characidae . Paralleled in node 273 and in Stichonodon insignis . Some trees: Paralleled in node 302 and in Microschemobrycon casiquiare .

8. Second humeral spot (342): (0> 1) present as a conspicuous vertical bar. Paralleled in Gymnocorymbus ternetzi and Hyphessobrycon bifasciatus .