Idiosoma clypeatum 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 : 23-27

Idiosoma clypeatum Rix & Harvey sp. n. Figs 14, 15, 25, 79-88, 89-91, 92-100, 374

Idiosoma ‘nigrum’ Main, 1957b: 440 (in part; cited specimens from E. of Ederga, N. of Gullewa, S. of Mullewa and E./SE. of Paynes Find). Ellis 2015: 242, 244, figs 1, 3, 4.

Type material.

Holotype male. Albion Downs, 70.1 km NNW. of Leinster (IBRA_MUR), Western Australia, Australia, 27°21'30"S, 120°21'33"E, dry pitfall trap, 28 August– 3 September 2008, Z. Hamilton, R. Teale (WAM T96452DNA_Voucher_126).

Paratype. 1 ♂, same data as holotype (WAM T96467).

Other material examined.

AUSTRALIA: Western Australia: 1 ♂, Albion Downs, 62.6 km NNW. of Leinster (IBRA_MUR), 27°25'03"S, 120°23'45"E, dry pitfall trap, 28 August– 3 September 2008, Z. Hamilton, R. Teale (WAM T96463); 1 ♂, same data (WAM T96510); 1 ♀, Blue Hill Range [not Blue Hills] (IBRA_YAL), 29°08'39"S, 116°53'04"E, burrow excavation, 14 October 2011, P.R. Langlands (WAM T117996DNA_Voucher_125); 1 juvenile, same data (WAM T117995); 1 juvenile, same data except 29°08'07"S, 116°52'49"E (WAM T117997); 1 juvenile, same locality data except 29°08'27"S, 116°52'39"E, 25 June 2010, L. Quinn, S. White (WAM T107333); 1 ♀, same locality data except 29°07'15"S, 116°45'18"E, 26-30 October 2012, S. White, F. Bokhari (WAM T127535); 1 ♀, same data except 29°07'29"S, 116°47'41"E (WAM T127536); 1 ♀, same data except 29°07'08"S, 116°46'56"E (WAM T127534); 1 ♀, Boolardy Station (IBRA_MUR), 27°03'46"S, 116°41'43"E, burrow excavation, 8 December 2014, A. Leung (WAM T136250DNA_Voucher_NCB_021); 1 ♂, Browns Soak, 20 miles N. of Lake Barlee on Youanmi-Pidgeon Rock Road (IBRA_MUR), ca. 29°00'S, 118°47'E, July–August 1957, W.H. Butler (WAM T139501); 1 ♀, ca. 16 km NE. of Coolcalalaya Homestead, Dampier- Bunbury Natural Gas Pipeline, site 6.07 (IBRA_YAL), 27°25'57"S, 115°11'02"E, in pipeline trench, 4 June 2006, P. Cullen (WAM T78246DNA_Voucher_64); 1 ♀, same data except ca. 21 km NE. of Coolcalalaya Homestead, 27°22'23"S, 115°11'07"E, 1 June 2006 (WAM T78252DNA_Voucher_137); 1 ♀, Dalgaranga Station (IBRA_MUR), 27°50'40"S, 117°08'14"E, 13 January 2010, M. Davis (WAM T108517DNA_Voucher_140); 1 ♀, 4 miles E. of Ederga (IBRA_YAL), 28°31'S, 116°28'E, 14 July 1955, B.Y. Main (WAM T144831); 1 ♀, same data (WAM T144802); 1 juvenile, same data (WAM T144832); 1 juvenile, same data (WAM T144833); 1 ♀, same data (WAM T144834); 1 ♂, Glen Station (IBRA_MUR), 26°34'23"S, 117°37'30"E, excavation, 10 May 2009, Ecologia (WAM T107368DNA_Voucher_132); 2 ♂, Glen Station, off Kalli Road (IBRA_MUR), 26°34'23"S, 117°37'30"E, wet pitfall trap, 5 May– 28 June 2009, N. Dight, L. Quinn (WAM T98142); 1 ♀, 46 miles NE. of Gutha, 8 miles N. of Mullewa (IBRA_YAL), 28°35'S, 116°24'E, 18 August 1953, B.Y. Main (WAM T144781); 1 ♂, Jack Hills, ca. 1 km SW. of Mount Hale (IBRA_MUR), 26°02'53"S, 117°15'13"E, burrow excavation, 24 May 2012, P. Langlands (WAM T136251); 1 ♂, same data (WAM T136252DNA_Voucher_NCB_022); 1 juvenile, same data except 18 May 2012 (WAM T136247); 1 juvenile, same data (WAM T136248); 1 juvenile, same data (WAM T136249); 1 ♂, Jack Hills, site 17 (IBRA_MUR), 26°07'S, 117°09'E, 24 August– 24 November 2006, Ecologia (WAM T139504); 1 ♀, Jack Hills, Creek Road, site 91, 18 October 2007, Ecologia staff (WAM T144762); 1 ♀, same data except site 79, 22 October 2007 (WAM T144761); 1 juvenile, Kadji Kadji Nature Reserve, 35 km NE. of Morawa (IBRA_ AVW), 29°15'36"S, 116°22'51"E, mammal pitfall, 6 August 2010, M. Bamford (WAM T110279DNA_Voucher_142); 1 ♀, Karara (IBRA_YAL), 29°10'42"S, 116°41'33"E, 12 January 2010, B. Durrant (WAM T108516DNA_Voucher_141); 1 ♀, Karara Station, ca. 21 km NE. of homestead (IBRA_YAL), 29°09'03"S, 116°54'24"E, mixed shrubland, Acacia /mallee, 10 October 2006, M. Bamford et al. (WAM T132582); 1 ♀, Mt Karara, quadrat 6.4 (IBRA_YAL), 29°10'50"S, 116°46'44"E, 29 June 2008, M. Bamford (WAM T91625); 1 ♀, Kirkalocka MMS Gold Mine (IBRA_MUR), 28°41'36"S, 117°46'56"E, 2-6 September 2011, S. White, M.C. Leng (WAM T116660); 1 juvenile, same data except 28°40'53"S, 117°45'04"E (WAM T116661); 1 ♀, Lakeside Station (IBRA_MUR), 27°37'11"S, 117°25'55"E, 12 January 2010, M. Davis (WAM T108030DNA_Voucher_139); 1 juvenile, 2 miles E. of Paynes Find (IBRA_MUR), 29°15'S, 117°48'E, 4 October 1955, B.Y. Main (WAM T144818); 1 ♀, 1 juvenile, same data (WAM T144819); 1 juvenile, same data (WAM T144820); 1 juvenile, same data (WAM T144821); 1 ♀, 10 juveniles, same data (WAM T144822); 1 ♀, same data (WAM T144823); 1 juvenile, same data (WAM T144824); 1 juvenile, same data (WAM T144825); 1 ♀, 24 miles SW. of Paynes Find on Great Northern Highway (IBRA_YAL), 29°21'S, 117°31'E, 4 November 1955, B.Y. Main (WAM T144798); 1 ♂, Urawa Nature Reserve, north, site ML7 (IBRA_YAL), 28°24'02"S, 115°34'34"E, wet pitfall traps, 15 September 1998-18 October 1999, B. Durrant, CALM Survey (WAM T139505); 1 ♂, Weld Range [no specific details] (IBRA_MUR), Ecologia (WAM T139581); 1 ♀, same locality data, 2 October 2007, B.Y. Main (WAM T144759); 1 ♀, same data (WAM T144760); 1 ♀, same locality data except 26°53'17"S, 117°43'05"E, 30 May 2010, J.D. Clark (WAM T136484); 2 ♂, Weld Range North, site WN1 (IBRA_MUR), 26°56'S, 117°38'E, 20-23 August 2007, Ecologia (WAM T139508); 1 ♂, same data except site WN2 (WAM T139509); 3 ♂, same data except site WN5 (WAM T139500); 1 ♂, same data except site WN6 (WAM T139507); 1 ♂, same data except site WN8 (WAM T139506); 1 juvenile, same data except site WN10, 26°47'47"S, 117°53'19"E, 3 September 2007 (WAM T144758); 1 ♂, same data except site WN11 (WAM T139503); 1 ♂, same data except site WN12 (WAM T139502); 1 ♀, Woolgorong (IBRA_YAL), 27°36'29"S, 116°42'42"E, 15 January 2010, M. Davis (WAM T108032DNA_Voucher_138); 1 ♀, Yakabindie (IBRA_MUR), 27°24'02"S, 120°41'29"E, targeted search, 21 January 2011, P. Bolton (WAM T110576DNA_Voucher_63); 1 ♀, same data except 27°17'27"S, 120°36'35"E (WAM T110581DNA_Voucher_136); 1 ♀, same data except 27°21'41"S, 120°40'59"E, 18 January 2011 (WAM T110579); 1 ♀, same data (WAM T110582); 1 ♀, same data (WAM T110575); 1 ♀, same data except 27°26'16"S, 120°36'35"E, 14 January 2011 (WAM T110580); 1 ♀, same data (WAM T110578); 1 ♀, 12 juveniles, same data (WAM T110577); 1 ♀, Yeelirrie, ca. 66.70 km SW. of Wiluna Airport (IBRA_MUR), 27°02'06"S, 119°42'55"E, hand collected, 16 March 2015, M. Bamford (WAM T135961); 1 ♀, same data except 27°02'07"S, 119°43'00"E (WAM T135962); 1 ♀, Yeelirrie Station (IBRA_MUR), 27°19'02"S, 120°12'18"E, excavation, 28 January– 4 February 2010, Ecologia (WAM T101942DNA_Voucher_160); 1 ♀, same data except 27°08'15"S, 119°53'20"E, 11 September 2010, Ecologia Staff (WAM T103475DNA_Voucher_135).

Etymology.

The specific epithet is derived from the Latin clypeatus (adjective: ‘shielded’, 'armed with a shield’), in reference to the highly sclerotised, phragmotic abdominal morphology of this species.

Diagnosis.

Idiosoma clypeatum is one of seven highly autapomorphic species in the polyphyletic 'sigillate complex’ (Fig. 25); members of this complex can be distinguished from all other species in the nigrum-group from south-western Australia (i.e., I. formosum , I. gardneri , I. gutharuka , I. incomptum , I. intermedium , I. jarrah , I. mcclementsorum , I. mcnamarai and I. sigillatum ) by the presence of well-defined lateral sclerotic strips on the male abdomen (e.g., Figs 32, 63, 256), and by the very heavily sclerotised, leathery, ‘shield-like’ morphology of the female abdomen (e.g., Figs 1-3, 9-12, 52, 74, 96). Males of I. clypeatum can be further distinguished from those of I. arenaceum by the shape of the SP4 sclerites, which are not elongate-oval (Fig. 85; cf. Fig. 63); from I. kwongan by the absence of semi-circular lateral indentations adjacent to the SP4 sclerites (Fig. 85; cf. Fig. 278, Key pane 13.1); from I. dandaragan , I. nigrum and I. schoknechtorum by the absence of a prominent sub-distal embolic apophysis (Key pane 14.3; cf. Key pane 14.1); and from I. kopejtkaorum by the more heavily setose morphology of metatarsus I (Fig. 86, Key pane 16.1; cf. Fig. 257, Key pane 16.2).

Females can be distinguished from those of I. arenaceum by the shape of the SP4 sclerites, which are not elongate-oval (Fig. 96, Key pane 22.2; cf. Fig. 74, Key pane 21.1); and from I. dandaragan , I. nigrum and I. schoknechtorum by the size of the SP4 sclerites, which are approximately half the size of the SP3 sclerites (Fig. 96, Key pane 22.2; cf. Figs 43, 52, 140, 346, Key panes 23.1-23.3) [NB. females of I. kwongan are unknown]. By our assessment, females of I. clypeatum are morphologically indistinguishable from those of I. kopejtkaorum ; males, molecular data (Fig. 25) or geographic distribution (Fig. 374) are required for accurate identification.

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. 86; cf. Fig. 109), and by the shape of the female eye group, which is broadly trapezoidal (Fig. 95; cf. Fig. 117).

Description (male holotype).

Total length 17.3. Carapace 7.4 long, 5.3 wide. Abdomen 8.2 long, 4.9 wide. Carapace (Fig. 79) dark chocolate-brown, with darker ocular region; lateral margins with uniformly-spaced fringe of porrect black setae; fovea procurved. Eye group (Fig. 82) trapezoidal (anterior eye row strongly procurved), 0.6 × as long as wide, PLE–PLE/ALE–ALE ratio 2.0; ALE almost contiguous; AME separated by less than their own diameter; PME separated by 4.0 × their own diameter; PME and PLE separated by slightly more than diameter of PME, PME positioned slightly posterior to level of PLE. Maxillae and labium without cuspules. Abdomen (Figs 80, 85) irregularly oval, dark brown in dorsal view with lateral sclerotic strips, dorso-lateral corrugations, and scattered dorsal sclerotic spots. Dorsal surface of abdomen (Fig. 80) more heavily setose anteriorly, with assortment of stiff, porrect black setae, each with slightly raised, dark brown sclerotic base. Posterior abdomen strongly sigillate (Figs 80, 85); SP2 sclerites irregular spots; SP3 sclerites very large and circular; SP4 sclerites broadly oval, almost subquadrate; SP5 obscured. Legs (Figs 86-88) variable shades of dark tan, with light scopulae on tarsi I–II; distal tibia I with pair of large prolateral clasping spurs oriented longitudinally. Leg I: femur 6.3; patella 3.3; tibia 4.2; metatarsus 4.7; tarsus 2.5; total 21.1. Leg I femur–tarsus /carapace length ratio 2.9. Pedipalpal tibia (Figs 89-91) 2.4 × longer than wide; RTA burr-like, with conical basal protuberance and field of retroventral spinules; digital process porrect, unmodified. Cymbium (Figs 89-91) setose, with field of spinules disto-dorsally. Embolus (Figs 89-91) broadly twisted and sharply tapering distally, with prominent longitudinal flange; embolic apophysis absent.

Description (female WAM T108516).

Total length 21.8. Carapace 8.3 long, 5.7 wide. Abdomen 9.9 long, 9.6 wide. Carapace (Fig. 92) tan, with darker ocular region; fovea procurved. Eye group (Fig. 95) trapezoidal (anterior eye row strongly procurved), 0.6 × as long as wide, PLE–PLE/ALE–ALE ratio 2.2; ALE almost contiguous; AME separated by approximately their own diameter; PME separated by 2.1 × their own diameter; 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. 97); labium without cuspules. Abdomen (Figs 93, 96) dark brown-black, corrugate and highly sclerotised, with leathery appearance typical of those species in the 'sigillate complex’ (see Fig. 25). Posterior face of abdomen (Fig. 96, Key pane 22.2) with truncate ‘shield-like’ morphology; SP3 sclerites very large and circular; SP4 sclerites oval; SP5 obscured by thickened cuticle. Legs (Figs 98-99) variable shades of 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 seven stout macrosetae; tarsus I with distal cluster of short macrosetae. Leg I: femur 5.0; patella 3.3; tibia 3.0; metatarsus 2.5; tarsus 2.0; total 15.8. Leg I femur–tarsus /carapace length ratio 1.9. Pedipalp tan, spinose on tibia and tarsus, with thick tarsal scopula. Genitalia (Fig. 100) with pair of short, obliquely angled spermathecae, each bearing dense field of glandular vesicles distally, and more sparsely distributed glandular field sub-distally.

Distribution and remarks.

Idiosoma clypeatum (formerly known by WAM identification code ‘MYG018’) has a widespread distribution in Western Australia’s inland arid zone, principally throughout the Yalgoo and Murchison bioregions where it is the only known species in the nigrum-group (excluding a population of I. formosum from the southern Yalgoo) (Fig. 374). It extends from near Paynes Find, the Blue Hill Range, Kadji Kadji Nature Reserve, and Karara in the south, north and north-east to at least Coolcalalaya Homestead, Jack Hills, Albion Downs, Yakabindie, and Yeelirrie. This distribution seems to be strongly correlated with annual rainfall of less than 250 mm. At the southern extent of its range it abuts the northern limit of the closely related species I. kopejtkaorum , and on the Geraldton Sandplains is replaced by I. arenaceum and I. kwongan (all four 'sigillate complex’ species together forming the northern clypeatum-clade; Fig. 25).

Idiosoma clypeatum was for a long time misidentified as I. nigrum , and indeed the 2013 threatened species assessment of I. nigrum prepared under the Commonwealth Environmental Protection and Biodiversity Conservation Act 1999 conflated the identification of these two species. Burrows are adorned with a ‘moustache-like’ arrangement of twig-lines (Figs 14, 15), and males have been collected wandering in search of females in late autumn, winter and spring, with a peak of activity in winter. Ellis (2015) summarises aspects of the biology of this species based on observations at the Weld Range.

Conservation assessment.

In 2017, Idiosoma clypeatum was formally assessed as 'priority 3' fauna; this assessment incorporated the latest taxonomic, geographic, and genetic data summarised in the current study (with a number of additional records also identified subsequently). It has a known extent of occurrence of over 120,000 km2 [120,465 km2], and while it therefore cannot be considered threatened under Criterion B, a 'priority 3' recommendation was made due to the widespread occurrence of this species in areas prospective for mining and mineral resources. Further close assessment under both Criteria A and B is warranted in the future.