Key to males of the known species of Dendrocephalus from Argentina

1 Frontal appendage branch 1V, anterior subbranch with apex acute............................................... 2

- Frontal appendage branch 1V, anterior subbranch with apex swollen............................................. 3

2 First thoracopod endopodite with basolateral projection not margined with spines; endopodite of thoracopod 2 without any basolateral projection......................................................................... D. conosuris

- Endopodites of thoracopods 1 and 2 with basolateral projection margined with short, mainly blunt spines, and surface of the projection sometimes ornamented with short rounded spines; endopodites of thoracopods 1–3, with distolateral corner lobiform, margined with spines................................................................ D. argentinus

3 Endopodites of first three pairs of thoracopods without any lateral projection; with a row of spines in the lateral edge of endopodites............................................................................... D. brasiliensis

- Endopodite of first thoracopod basodistally elongated reaching twice the length of endopodite of thoracopod 2, with a curved, sharp distolateral projection margined with stout spines; prominent distomedial corner margined with stout spines; lateral margin of endopodite with no or few short spines; endopodite of thoracopod 2 without projections, lateral edge with a row of spines.................................................................................... D. cervicornis