Autapomorphies of Hemigrammus unilineatus:

1. Number of supraneurals (280): (0> 1) five or more. Reversal of synapomorphy 2 of node 223. Some trees: Paralleled in Hasemania nana .

Some trees:

2. Ventral extent of third infraorbital (64): (0> 1) not reaching horizontal arm of preopercle, at least anteriorly. (k13-14). Reversal of synapomorphy 2 of node 292.

3. Length of ascending process of premaxilla (104): (1> 0) reaching at least one-third of length of nasal. (k13-14).

4. Number of 2n chromosomes (363): (0> 1) 52 or more. (k9- 12). Paralleled in the Characinae and Serrasalmidae, in node 196, and in Chalceus macrolepidotus, Hyphessobrycon herbertaxelrodi, Markiana nigripinnis, and Rhaphiodon vulpinus .