Idiosoma mcclementsorum Rix & Harvey

Rix, Michael G., Huey, Joel A., Cooper, Steven J. B., Austin, Andrew D. & Harvey, Mark S., 2018, Conservation systematics of the shield-backed trapdoor spiders of the nigrum-group (Mygalomorphae, Idiopidae, Idiosoma): integrative taxonomy reveals a diverse and threatened fauna from south-western Australia, ZooKeys 756, pp. 1-121 : 52-55

Idiosoma mcclementsorum Rix & Harvey sp. n. Figs 8, 24, 25, 285-294, 295-297, 298-306, 375

Idiosoma ' sigillatum ' Main, 1957b: 439 (in part; cited specimens from SW. of Bolgart, Chittering Lakes, Mogumber, E. of Mogumber and Gillingarra).

Type material.

Holotype male. Julimar Conservation Park, Heine Road, site JB10 (IBRA_JAF), Western Australia, Australia, 31°27'03"S, 116°14'42"E, wet pitfall traps, 15 September 1998-4 November 1999, L. King, CALM Survey (WAM T139471).

Paratypes. 1 ♂, same data as holotype (WAM T139472); 1 ♀, Julimar Conservation Park, Mortimer Road (IBRA_JAF), Western Australia, Australia, 31°28'46"S, 116°12'18"E, hand collected, 23 April 2016, M.G. Rix, M.S. Harvey (WAM T139469DNA_Voucher_NCB_001).

Other material examined.

AUSTRALIA: Western Australia: 1 ♀, 7 juveniles, 9.6 miles SW. of Bolgart (IBRA_JAF), 31°22'S, 116°25'E, 4 June 1953, B.Y. Main (WAM T144861); 1 juvenile, Chittering Lake, just E. of [Great] Northern Highway on Chittering Road (IBRA_JAF), 31°26'S, 116°05'E, 10 October 1953, B.Y. Main (WAM T144863); 1 juvenile, Gillingarra (IBRA_JAF), 30°56'S, 116°03'E, 4 May 1956, B.Y. Main (WAM T144867); 1 ♀, S. of 7 Mile Well Nature Reserve (IBRA_JAF), 31°04'03"S, 116°12'13"E, burrow excavation, 6 March 2015, J. Clark (WAM T139832DNA_Voucher_NCB_015); 1 ♀, 5 miles E. of Mogumber in Moore River (IBRA_JAF), 31°01'S, 116°05'E, 4 May 1953, B.Y. Main (WAM T144860); 1 ♀, 10.6 miles N. of Mooliabeenee turnoff from Great Northern Highway (IBRA_JAF), 31°13'S, 116°05'E, 4 March 1953, B.Y. Main (WAM T144857); 1 juvenile, Moore River gorge at Mogumber (IBRA_JAF), 31°02'S, 116°02'E, 4 March 1953, B.Y. Main (WAM T144859); 1 ♂, Toodyay (IBRA_AVW), 31°33'S, 116°28'E, on verandah, January 1997, F. Turnbull (WAM T44388); 1 ♂, Toodyay, Lot 2516 Bindoon Road (IBRA_JAF), 31°33'S, 116°28'E, 1 January 1993, M. & M. Heath (WAM T29779).

Etymology.

The specific epithet is named in honour of James and Meredith McClements, in recognition of their generous support for the Western Australian Museum Foundation.

Diagnosis.

Idiosoma mcclementsorum is one of nine south-western Australian species in the intermedium- and sigillatum-clades which does not belong to the distinctive 'sigillate complex’ (Fig. 25); these nine species can be distinguished from those 'sigillate complex’ taxa (i.e., I. arenaceum , I. clypeatum , I. dandaragan , I. kopejtkaorum , I. kwongan , I. nigrum and I. schoknechtorum ) by the absence of well-defined lateral sclerotic strips on the male abdomen (e.g., Figs 151, 212, 234), and by the significantly less sclerotised morphology of the female abdomen (which may be strongly corrugate but never leathery and ‘shield-like’) (e.g., Figs 4, 7, 8, 159, 220, 242). Males of I. mcclementsorum can be further distinguished from those of I. gutharuka and I. incomptum by the presence of enlarged (i.e., clearly visible) SP4 sclerites (Fig. 291; cf. Figs 186, 199); from I. formosum , I. gardneri , I. intermedium , I. mcnamarai and I. sigillatum by the colour of the legs, which are bi-coloured with strongly contrasting bright yellow or orange-yellow femora (Fig. 292; cf. Figs 152, 174, 213, 314, 358); and from I. jarrah by the size of the SP3 and SP4 sclerites, which are relatively large (Fig. 291; cf. Fig. 234).

Females can be distinguished from those of I. formosum , I. intermedium , I. jarrah and I. mcnamarai by the presence of reinforced, sclerotised ridges on the abdomen, these separated by longitudinal rows of less sclerotised cuticle (Figs 299, 302; cf. Figs 159, 162, 220, 223, 242, 245, 321, 324); and from I. sigillatum by the larger size of the SP3 sclerites (Fig. 302; cf. Fig. 368) [NB. females of I. gardneri , I. gutharuka , and I. incomptum are unknown].

This species can also be distinguished from I. corrugatum (from the Eyre Peninsula of South Australia) by the shape of the prolateral clasping spurs on the male tibia I, which are oriented longitudinally (Fig. 293; cf. Fig. 109), and by the shape of the female eye group, which is broadly trapezoidal (Fig. 301; cf. Fig. 117).

Description (male holotype).

Total length 21.2. Carapace 9.9 long, 7.7 wide. Abdomen 9.1 long, 6.6 wide. Carapace (Fig. 285) dark chocolate-brown, with darker ocular region; lateral margins with uniformly-spaced fringe of porrect black setae; fovea slightly procurved. Eye group (Fig. 288) trapezoidal (anterior eye row strongly procurved), 0.7 × as long as wide, PLE–PLE/ALE–ALE ratio 2.1; ALE almost contiguous; AME separated by less than their own diameter; PME separated by 2.8 × their own diameter; PME and PLE separated by slightly more than diameter of PME, PME positioned in line with level of PLE. Maxillae and labium without cuspules. Abdomen (Figs 286, 291) irregularly oval, dark tan in dorsal view with paler tan striations, dorso-lateral corrugations, and scattered dorsal sclerotic spots. Dorsal surface of abdomen (Fig. 286) more heavily setose anteriorly, with assortment of stiff, porrect black setae, each with slightly raised, dark brown sclerotic base. Posterior abdomen moderately sigillate (Figs 286, 291); SP2 sclerites irregular spots; SP3 sclerites large and circular, each with unsclerotised triangular ‘corner’ laterally; SP4 sclerites subcircular, each surrounded by chevron-like pad of unsclerotised cuticle laterally; SP5 obscured. Legs (Figs 292-294) bicoloured, variable shades of dark brown on patellae, tibiae, metatarsi and tarsi, and bright tan-yellow on femora, with light scopulae on tarsi I–II; distal tibia I with pair of large prolateral clasping spurs oriented longitudinally. Leg I: femur 8.7; patella 4.6; tibia 6.3; metatarsus 6.6; tarsus 3.5; total 29.7. Leg I femur–tarsus /carapace length ratio 3.0. Pedipalpal tibia (Figs 295-297) 2.2 × longer than wide; RTA burr-like, with conical basal protuberance and field of retroventral spinules; digital process porrect, unmodified. Cymbium (Figs 295-297) setose, with field of spinules disto-dorsally. Embolus (Figs 295-297) broadly twisted and sharply tapering distally, with prominent longitudinal flange and triangular (sub-distal) embolic apophysis.

Description (female WAM T139469).

Total length 22.4. Carapace 10.0 long, 7.3 wide. Abdomen 9.6 long, 9.3 wide. Carapace (Fig. 298) dark tan and chocolate-brown, with darker ocular region; fovea procurved. Eye group (Fig. 301) trapezoidal (anterior eye row strongly procurved), 0.6 × as long as wide, PLE–PLE/ALE–ALE ratio 2.5; ALE almost contiguous; AME separated by approximately their own diameter; PME separated by 3.0 × diameter of left PME (right PME disfigured); PME and PLE separated by more than diameter of PME, PME positioned in line with level of PLE. Maxillae with field of cuspules confined to inner corner (Fig. 303); labium without cuspules. Abdomen (Figs 299, 302) truncate, tan, with reinforced dark maroon-black corrugate ridges separated by longitudinal rows of less sclerotised cuticle, each ridge bearing row of modified stout setae. Posterior face of abdomen (Fig. 302) with rudimentary shield-like morphology; SP3 sclerites large and circular with irregular margins; SP4 sclerites subcircular; SP5 sclerites small and oval. Legs (Figs 304-305) variable shades of dark tan; scopulae present on tarsi and metatarsi I–II; tibia I with one stout pro-distal macroseta and row of five longer retroventral macrosetae; metatarsus I with eight stout macrosetae; tarsus I with distal cluster of short macrosetae. Leg I: femur 6.6; patella 4.0; tibia 4.2; metatarsus 3.2; tarsus 2.4; total 20.4. Leg I femur–tarsus /carapace length ratio 2.0. Pedipalp dark tan, spinose on tibia and tarsus, with thick tarsal scopula. Genitalia (Fig. 306) with pair of short, rounded-subtriangular spermathecae, each bearing dense field of glandular vesicles distally, and more sparsely distributed glandular field sub-distally.

Distribution and remarks.

Idiosoma mcclementsorum (formerly known by WAM identification code ‘MYG474’) (Fig. 8), a member of the yellow legs-clade within the diverse sigillatum-clade (Fig. 25), is a rare species with a highly restricted distribution in the northern Jarrah Forest bioregion of south-western Western Australia, from Chittering Lakes, Julimar, and Toodyay north to Gillingarra. South of the Avon Valley it is replaced by its closely related sister species I. jarrah , both of which are characterised by yellow leg femora in males (Figs 235, 292). Burrows are adorned with a ‘moustache-like’ arrangement of twig-lines (Fig. 24), and have been found on sandy substrates overlaying laterite. Both males from Toodyay were collected in January, and both males from Julimar were collected between September and November, suggesting that this species may be an unusual spring and summer breeder.

Conservation assessment.

Idiosoma mcclementsorum has a known extent of occurrence (EOO) of nearly 1,500 km2 [1,347 km2], although this value is possibly a slight underestimate. The area of occupancy within that range is difficult to estimate, but is unlikely to be larger than 100 km2. Given: (i) this geographic range; (ii) the sampling effort that has occurred in surrounding areas as a result of a major biotic survey (see Keighery 2004) and a long history of incidental collecting; (iii) the occurrence of the species at <10 severely fragmented sites; and (iv) the continuing decline in the area, extent and/or quality of habitat north-east of Perth, this species is considered Endangered (B1ab[iii] + B2ab[iii]). Further close assessment under both Criteria A and B will be crucial to the continued survival of this species.