Idiosoma gardneri 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 : 36

Idiosoma gardneri Rix & Harvey sp. n. Figs 167-176, 177-179, 375

Type material.

Holotype male. Mount Lesueur [Lesueur National Park] (IBRA_GES), Western Australia, Australia, 30°10'S, 115°12'E, pitfall trap, 1989, K. Gaull (WAM T139528).

Etymology.

The specific epithet is named in honour of the late Charles Gardner (1896-1970), former curator of the Western Australian Herbarium, whose conservation efforts were instrumental in protecting the Lesueur National Park for posterity.

Diagnosis.

Idiosoma gardneri 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. gardneri can be further distinguished from those of I. gutharuka and I. incomptum by the presence of enlarged (i.e., clearly visible) SP4 sclerites (Fig. 173; cf. Figs 186, 199); from I. jarrah and I. mcclementsorum by the colour of the legs, which do not have strongly contrasting bright yellow or orange-yellow femora (Fig. 174; cf. Figs 235, 292); from I. formosum , I. intermedium and I. mcnamarai by the presence of well-defined dorso-lateral abdominal corrugations and striations (Figs 168, 173; cf. Figs 146, 151, 207, 212, 308, 313, Key pane 9.2); and from I. sigillatum by the larger, more closely spaced SP3 sclerites and the larger SP4 sclerites (Fig. 173, Key pane 10.2; cf. Fig. 357, Key pane 10.1). Males of this species can also be distinguished from those of I. corrugatum (from the Eyre Peninsula of South Australia) by the shape of the prolateral clasping spurs on tibia I, which are oriented longitudinally (Fig. 175; cf. Fig. 109). Females are unknown.

Description (male holotype).

Total length 19.2. Carapace 8.1 long, 6.2 wide. Abdomen 8.4 long, 5.5 wide. Carapace (Fig. 167) dark tan, with darker ocular region; lateral margins with uniformly-spaced fringe of porrect black setae; fovea procurved. Eye group (Fig. 82) trapezoidal; anterior eye row developmentally disfigured, with ALE absent and AME each with multiple asymmetrical ocelli; PME separated by 3.6 × their own diameter; PME and PLE separated by slightly more than diameter of PME, PME positioned slightly posterior to level of PLE. Maxillae with field of small cuspules confined to inner corner; labium without cuspules. Abdomen (Figs 168, 173) oval, dark brown in dorsal view with paler tan striations, dorso-lateral corrugations and scattered dorsal sclerotic spots. Dorsal surface of abdomen (Fig. 168) more heavily setose anteriorly, with assortment of stiff, porrect black setae, each with slightly raised, dark brown sclerotic base. Posterior abdomen moderately sigillate (Figs 168, 173); SP2 sclerites irregular, comma-shaped spots; SP3 sclerites large and circular; SP4 sclerites subquadrate, each surrounded by chevron-like pad of unsclerotised cuticle laterally; SP5 obscured. Legs (Figs 174-176) 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 7.2; patella 3.7; tibia 5.2; metatarsus 5.6; tarsus 3.3; total 25.0. Leg I femur–tarsus /carapace length ratio 3.1. Pedipalpal tibia (Figs 177-179) 2.3 × longer than wide; RTA burr-like, with conical basal protuberance and field of retroventral spinules; digital process porrect, unmodified. Cymbium (Figs 177-179) setose, with field of spinules disto-dorsally. Embolus (Figs 177-179) broadly twisted and sharply tapering distally, with prominent longitudinal flange and triangular (sub-distal) embolic apophysis.

Distribution and remarks.

Idiosoma gardneri (formerly known by WAM identification code ‘MYG476’) is known only from Lesueur National Park, in the southern Geraldton Sandplains bioregion of south-western Western Australia (Fig. 375). Only a single specimen has ever been collected, and nothing is known of its biology. It is most similar to I. sigillatum , and the two are likely to be sister species.

Conservation assessment.

Due to the known occurrence of this species at only a single site, in an area with a relatively large amount of high quality and poorly surveyed heathland habitat, we consider it data deficient for the purposes of conservation assessment.