Identification key for Oligoxystre. Modified from Guadanucci (2007). Female of Oligoxystre auratum is undescribed.

Males

1 Male palpal bulb embolus with small subapical keel (Guadanucci 2007: Figs 2-5, 26-28) .................................................................................................2

– Embolus without keel (Figs 1-3; Guadanucci 2007: Figs 22-23, 31-32, 35- 36).............................................................................................................. 3

2 Embolus long and thin, slightly bent distally (Guadanucci 2007: Figs 26- 28)...................................................................................... O. dominguense

– Embolus short, strongly bent medially (Guadanucci 2007: Figs 2-5) ........ O. bolivianum

3 Bulb twisted on itself, prolonged by long collar, depressed at base and thin apical end, curved (Vellard 1924: 152, pl. 10 Fig. 38)................ O. auratum

– Bulb not as above........................................................................................4

4 Embolus more than 3 times longer than tegulum (Guadanucci 2007: Figs 22-23); spiders with cephalothorax and abdomen dark ventrally; white setae over dorsal region of cephalothorax (Guadanucci 2007: Fig. 38) O. caatinga

– Embolus less than 2.5 times tegulum length (Figs 1-3, Guadannuci 2007: Figs 31-23, 35-36); spiders with coloration on ventral portion browish or yellowish; without white setae on body.......................................................5

5 Leg I tibial spur positioned in a perpendicular angle in relation to the tibia axis (Figs 4-5); spiders with carapace, chelicerae, abdomen and legs covered dorsally and ventrally with metallic blue setae (Fig. 7)................................... ............................................................................. O. diamantinensis sp. n.

– Leg I tibial spur with branches positioned in an inclined angle in relation to the tibia axis (Guadanucci 2007: Figs 30, 34); spiders with carapace and legs browish or reddish ...................................................................................... 6

6 Embolus slightly bent distally (Guadanucci 2007: Figs 31 32); carapace and legs brown ............................................................................ O. tucuruiense

– Embolus slightly curved distally (Guadanucci 2007: Figs 35-36); carapace and basal portion of legs reddish and distal portions of legs dark (Guadanucci 2007: Fig. 39)........................................................................... O. rufoniger

Females

1 Spermatheca receptacula as long as wide (Guadanucci 2007: Fig. 6) ............. ............................................................................................. O. bolivianum

– Spermatheca receptacula longer than wide (Figs 6; Guadanucci 2007: Figs 24, 29, 33, 37)............................................................................................ 2

2 Spermatheca receptacula without lateral lobes (Figs 6; Guadanucci 2007: Figs 24, 29)........................................................................................................3

– Spermathecae receptacula with at least one lateral lobe (Guadanucci 2007: Figs 29, 33, 37)...........................................................................................4

3 Spermatheca receptacula long, with small apical lobes of roughtly the same size (Guadanucci 2007: Fig. 24); white setae over dorsal region of cephalothorax, ventral cephalothorax and abdomen very dark ................ O. caatinga

– Spermatheca receptacula with a large lobe surrounded by other smaller lobes (Fig. 6); spiders with carapace, chelicerae, abdomen and legs covered dorsally and ventrally with metallic blue setae (Fig. 8) ....... O. diamantinensis sp. n.

4 Spermatheca receptacula very long and thin, with small lobes over entire length (Guadanucci 2007: Fig. 29) ..................................... O. dominguense

– Spermatheca receptacula long, with wide base, bearing lateral lobe towards outside (Guadanucci 2007: Figs 33, 37) ..................................................... 5

5 Lateral lobe bifurcated (or partly bifurcated) (Guadanucci 2007: Fig. 33); carapace and legs brown........................................................ O. tucuruiense

– Lateral lobe not bifurcated (Guadanucci 2007: Fig. 37); carapace and basal region of legs reddish, apical region of legs dark ........................ O. rufoniger