Figs. 7, 59, 100, 101.

Type material: AUSTRALIA: Western Australia: holotype male, Ravensthorpe Ranges South, 235 m elevation, 33°38’02”S, 120°10’55”E, hand collected under rocks, 15 May 2007, M.C. Leng, M.L. Moir, S. Comer (WAM T 83220). Paratypes: 3 males, 5 females, collected with holotype (WAM T 80858); 4 males, 3 females, Mount Chester, Ravensthorpe Ranges South, 319 m elevation, 33°36’18”S, 120°08’34”E, hand collected under rocks, 10 September 2007, M.C. Leng (WAM T 81295); 4 males, 8 females, Ravensthorpe Ranges South, 176 m elevation, 33°34’51”S, 120°08’17”E, hand collected under rock, 12 September 2007, M.C. Leng, J. Newell (WAM T 81299); 1 male, 6 females, Mount Desmond Lookout, Ravensthorpe Ranges South, 336 m elevation, 33°36’51”S, 120°09’08”E, hand collected in leaf litter and under rock, 13 September 2007, M.C. Leng, J. Newell (WAM T 81292).

Other material examined: AUSTRALIA: Western Australia: 1 female, collected with holotype (WAM T 80857); 4 males, 3 females, 14 juveniles, Mount Chester, Ravensthorpe Ranges South, 319 m elevation, 33°36’18”S, 120°08’34”E, tullgren funnel leaf litter extraction, 24 May 2007, M.C. Leng, M.L. Moir (WAM T 80994); 24 males, 24 females, Mount Chester, Ravensthorpe Ranges South, 319 m elevation, 33°36’18”S, 120°08’34”E, hand collected under rocks, 10 September 2007, M.C. Leng (WAM T 80988); 10 males, 7 females, Mount Desmond Lookout, Ravensthorpe Ranges South, 336 m elevation, 33°36’51”S, 120°09’08”E, hand collected in leaf litter and under rock, 16 May 2007, M.C. Leng, M.L. Moir (WAM T80863, T80862); 10 males, 26 females, Mount Desmond Lookout, Ravensthorpe Ranges South, 336 m elevation, 33°36’51”S, 120°09’08”E, tullgren funnel leaf litter extraction, 16 May 2007, M.C. Leng, M.L. Moir (WAM T 80866); 13 males, 16 females, Ravensthorpe Ranges South, 242 m elevation, 33°37’06”S, 120°09’45”E, hand collected in leaf litter, under rotting logs and bark, 15 May 2007, M.C. Leng, M.L. Moir (WAM T 80851– T 80852); 2 males, 10 females, Ravensthorpe Ranges South, 253 m elevation, 33°36’56”S, 120°09’43”E, hand collected in leaf litter and under bark, 16 May 2007, M.C. Leng, M.L. Moir (WAM T 80859– T 80860); 17 males, 12 females, Ravensthorpe Ranges South, 155 m elevation, 33°34’34”S, 120°08’29”E, hand collected in leaf litter and under rock, 19 May 2007, M.C. Leng, M.L. Moir (WAM T 80913– T 80914); 12 males, 7 females, Ravensthorpe Ranges South, 218 m elevation, 33°38’19”S, 120°11’16”E, hand collected in leaf litter and under rock, 28 May 2007, M.C. Leng, M.L. Moir (WAM T 88779– T 88781, 81013); 8 males, 13 females, Ravensthorpe Ranges Mid, 152 m elevation, 33°34’45”S, 120°09’25”E, hand collected in leaf litter and under rock, 24 May 2007, M.C. Leng, M.L. Moir (WAM T 81004); 28 males, 39 females, Ravensthorpe Ranges Mid, 201 m elevation, 33°34’59”S, 120°07’36”E, hand collected in leaf litter and under rock, 28 May 2007, M.C. Leng, M.L. Moir (WAM T81027–81028); 41 males, 43 females, Ravensthorpe Ranges North, 279 m elevation, 33°32’35”S, 120°06’17”E, hand collected in leaf litter and under rock, 21 May 2007, M.C. Leng, M.L. Moir (WAM T 80945– T 80946); 30 males, 16 females, Archer Drive Lookout, Ravensthorpe Ranges North, 383 m elevation, 33°30’55”S, 120°02’52”E, hand collected in leaf litter and under rock, 22 May 2007, M.C. Leng, M.L. Moir (WAM T 80962– T 80963); 3 males, 7 females, Ravensthorpe Ranges North, 379 m elevation, 33°31’13”S, 120°03’34”E, hand collected under rock, 23 May 2007, M.C. Leng, M.L. Moir (WAM T 80976); 6 males, 20 females, Ravensthorpe Ranges North, 314 m elevation, 33°31’48”S, 120°04’20”E, hand collected in leaf litter and under rocks, 23 May 2007, M.C. Leng, M.L. Moir (WAM T 80978); 1 male, Ravensthorpe Ranges North, 314 m elevation, 33°31’48”S, 120°04’20”E, tullgren funnel leaf litter extraction, 23 May 2007, M.C. Leng, M.L. Moir (WAM T 80981).

Etymology: This species is named for Neil Gibson, who facilitated a research project in the Ravensthorpe Range in which many Atelomastix specimens were collected.

Diagnosis: Atelomastix gibsoni differs from all other species of the genus as the male gonopod sclerite b is greatly enlarged distally forming a large wedge-shape that extends to overlap the broad distal hood of sclerite a. Sclerite c is reduced in size, broad sub-distally and tapering slightly to a broad slightly curved tip, with a slight concavity on the externo-lateral surface where setae are situated.

Description: Male (holotype). Colour: generally chocolate-brown, legs, anal segment, and antennae light brown, mouthparts slightly lighter; prozonites chocolate brown, metazonites chocolate brown to light fawn in preserved specimens.

Body: ca. 24 mm long and ca. 1.8 mm wide at collum. With 56 trunk segments, 101 pairs of legs, last 2 segments without legs.

Head: with ca. 34 ocelli (Fig. 59), arranged in 6 rows (2: 7: 7: 7: 6: 5).

Gonopods: anterior gonopods (Figs. 100, 101) with medium sclerotisation, 2.3 times longer than broad; sclerite a with swollen base that forms broad, curved distal hood that overlaps and extends beyond tip of sclerite b; upper distal face of sclerite a with 24–30 (n=2) short blunt setae; pseudoflagellum relatively short and partially visible beneath broad distal hood; sclerite b very broad and enlarged distally, forming a wedge shape, with 4–8 (n=2) short setae; basal process of sclerite b very short, 0.01 times length of main process; sclerite c shorter than sclerite b, slightly concave on externo-lateral surface, slightly tapering to blunt rounded tip, with 1 seta on interno-lateral side of sclerite c and 5 setae within externo-lateral concavity of sclerite c (n=2); subbasal setae absent where sclerites overlap and group of 10–12 (n=2) short setae sub-basally on sclerite c; posterior gonopods inconspicuous, small, with several small setae on interno-lateral face of each gonopod.

Dimensions (mm): holotype male (paratype male, WAM T80858): length ca. 24, width ca. 1.5, L/W=16.0; sclerite a 0.944 / 0.419 (0.880 / 0.416), setae 24 (30); sclerite b 0.320 (0.294), basal process of sclerite b 0.01 (0.01), setae 4 (8); sclerite c 0.582 (0.563), setae 1+5 (1+5).

Female. Similar to male, other than sexual characters, and slightly larger.

Distribution and habitat: This species is known from a number of sites in the Ravensthorpe Ranges (Fig. 7) characterised by Hakea, Banksia, Eucalyptus woodlands and mallee heath and was found amongst leaf litter and under rotting logs, bark and rocks.