Table 1. Comparative characters among the species assigned to the Trichomycterus stawiarski group and its possible sister taxon T. perkos.

	T. crassicaudatus	T. igobi	T. stawiarski	T. ytororo, sp. nov.	T. perkos
Procurrent caudal–fin rays: thickness	thickly ossified and rigid	thickly ossified and rigid	thickly ossified and rigid	thickly ossified and rigid	thin and flexible
Dorsal procurrent caudal–fin rays: extension	over the tips of twelve neural spine	over the tips of at least ten neural spines	over the tips of thirteen neural spines	over the tips of thirteen neural spines	over the tips of less than 8 neural spines
Dorsal procurrent caudal–fin rays: number	24–26	24	27–29	31–35	14–17
Ventral procurrent caudal–fin rays: number	17–18	13	17	13	12–14
Branchiostegal rays: number	11	10–11	10	9	9–10
Caudal–fin distal margin in adults: shape	forked	truncate	truncate	rounded	rounded
Trunk canal pores: number	5–7	2	2–5	4–7	2
Pectoral–fin rays: number	i,7	i,7	i,6	i,7	i,5–6
Vertebrae: number	35–36	37	39	37–38	39–41
Extensor tentaculi muscle: origin	?	?	suspensorium and neurocranium	suspensorium and neurocranium	suspensorium