Austrarchaea Forster & Platnick, 1984

Rix, Michael G. & Harvey, Mark S., 2011, Australian Assassins, Part I: A review of the Assassin Spiders (Araneae, Archaeidae) of mid-eastern Australia, ZooKeys 123, pp. 1-100 : 7-10

Genus Austrarchaea Forster & Platnick, 1984

Austrarchaea Forster & Platnick, 1984: 21; Platnick 1991b: 259; Main 1995: 151; Harvey 2002a: 35.

Type species.

Archaea nodosa Forster, 1956, by original designation.

Diagnosis.

Species of Austrarchaea can be distinguished from all other extant Archaeidae (i.e. Malagasy and African species of Eriauchenius and Afrarchaea ) by the presence of numerous, clustered spermathecae in females (Figs 5D, 10G, 14G) and by the presence of a long, wiry embolus on the pedipalp of males (Figs 10E, 15E, 27E) ( Forster and Platnick 1984, Wood 2008). The remarkable, elevated shape of the carapace (Figs 4A-C, 10A-B) and the very long chelicerae (Figs 4B, 4D) will also immediately separate this genus from all other Australian spiders.

Description.

Small, haplogyne, araneomorph spiders; total length 2.5 to 5.0.

Colouration: Body colouration cryptic and relatively uniform across species, usually with only subtle intraspecific variation in abdominal patterning; carapace, sternum and chelicerae tan brown to dark reddish-brown, interspersed with darker regions of granulate cuticle (Fig. 5), covered in highly reflective setae; legs tan-brown to darker reddish-brown, with pattern of darker annulations on distal segments; abdomen mottled with beige and variable hues of grey-brown (Figs 5E-G), with darker sclerites, scutes and sclerotic spots (Figs 5A-B); paler beige markings due to reflective, subcuticular guanine crystals (Fig. 5B); antero-lateral face of abdomen always with large, humeral patch of reflective guanine crystals (Figs 5A, 5E-G).

Cephalothorax: Carapace greatly elevated anteriorly (CH/CL ratio usually 2.0-2.4; Fig. 6), with raised, highly modified pars cephalica forming ‘neck’ and bulbous ‘head’ (see Wood 2008) (Figs 4A-C); ‘neck’ with concomitantly long diastema (see Schütt 2002) between cheliceral bases and anterior margin of carapace, fused along entire length with sclerotised cuticle (Fig. 4C); cheliceral bases emanating from broad, fully-enclosed cheliceral foramen situated at front of ‘head’ (Figs 4A-B); posterior ‘head’ region usually also bearing two pairs of rudimentary protrusions or ‘horns’, each typically terminating in a short, thickened seta (Fig. 4A). Carapace with densely granulate cuticular microstructure (Fig. 4G), covered in larger setose tubercles arranged in clusters or distinct rows (Figs 4C, 4E); each tubercle bearing single densely plumose or ciliate seta; setose tubercles largest on ‘neck’ and pars thoracica (Figs 4C, 4E). Eight eyes present on anterior margin of ‘head’, in four widely separated diads (Figs 4A-B); AME largest, widely separated, directed antero-laterally on rounded ocular bulge (Fig. 4B); PME situated closely posterior to AME, directed obliquely on postero-lateral side of ocular bulge; lateral eyes contiguous, with shared raised bases, directed ventro-laterally on widest lateral margin of ‘head’ (Figs 4A-B). Sternum longer than wide, covered in setose tubercles; lateral margins separated from dorsal pleural sclerite extending between coxae I-IV. Labium subtriangular, not fused to sternum, directed antero-ventrally at oblique angle to sternum; labrum with pair of divergent projections on anterior surface. Maxillae large (Fig. 4C), straddling labium and labrum, converging distally; serrula a single row of teeth. Chelicerae very long, spear-like, distally divergent (Figs 4B, 4D, 4F), usually with proximal bulging projection (Fig. 4B); both sexes with oval, ectal stridulatory file adjacent to pedipalps (Fig. 4F); males usually also with brush (Figs 4F, 12C, 19C, 22C), short comb (Figs 14C, 18C) or dense tuft (Figs 16C, 17C) of accessory setae on anterior face of paturon. Chelicerae armed with three rows of peg teeth; anterior (prolateral) row with two peg teeth near tip of fang; posterior (retrolateral) row with single peg tooth near tip of fang; median (prolateral) row with more than 15 peg teeth extending along inner prolateral margin of paturon to near base of fang; median row with approximately nine porrect, comb-like peg teeth adjacent to fang, several larger, flattened, spiniform peg teeth near tip of fang, and additional progressively shorter, spiniform peg teeth along inner paturon (Fig. 4D); cheliceral retromargin also with four or five true teeth and prominent cheliceral gland mound.

Legs and female pedipalp: Legs (longest to shortest) 1 –4–2– 3, covered with short plumose setae; spines absent; patella I long, greater than one-third length of femur I. Trichobothria present on tibiae and metatarsi of legs; tibiae I-IV each with two trichobothria; metatarsi I-IV each with single trichobothrium; bothrial bases with strongly ridged hood. Tarsi shorter than metatarsi, with capsulate tarsal organ and three claws; tarsi, metatarsi and distal tibiae of legs I-II usually with ventral and pro-ventral rows of moveable, spatulate setae. Female pedipalp with long, porrect trochanter and small tarsal claw; tibia with two dorsal trichobothria.

Abdomen: Abdomen arched anteriorly, rounded-subtriangular in lateral view, usually with four to six large hump-like tubercles on dorsal surface (Figs 5A, 5E-G); cuticle covered with short plumose setae and numerous sclerotic spots (Figs 5A-B). Epigastric region with sclerotised (setose) book lung covers and dorsal and ventral plates surrounding pedicel (Fig. 5C) (plates fused in males); dorsal pedicel plate with transverse ridges; females with median genital plate and sclerotised lateral sigillae (Figs 5C-D); males with broad dorsal scute fused anteriorly to epigastric sclerites, with or without additional paired sclerites associated with hump-like tubercles (Fig. 5A). Six spinnerets, surrounded by thickened cuticle; ALS largest, PMS smallest; colulus absent. Posterior pair of divided tracheal spiracles situated anterior to spinnerets; males also with transverse row of epiandrous gland spigots situated closely anterior to epigastric furrow.

Genitalia: Female genitalia haplogyne, with sclerotised, strongly arched genital plate anterior to epigastric furrow (Figs 5C-D); internally with gonopore leading to large, spherical membranous bursa (Fig. 17G; see also Forster and Platnick 1984, fig. 57) overlying two separate, radiating clusters of sclerotised anterior spermathecae (Figs 5D, 10G, 14G, 19G). Male pedipalp with complex, expandable pyriform bulb (Figs 10E, 19E, 23E, 24E), consisting of smooth tegulum, proximal ‘subtegulum’ and associated tegular groove with basal haematodocha (Figs 10E, 23E, 27E) (similar to Mecysmaucheniidae and potentially analogous to the subtegular division of Entelegynae); distal tegulum with excavate, rimmed cavity surrounding massive, inflatable haematodochal complex incorporating distal embolus, basal embolic sclerite and multiple tegular sclerites (Figs 26D, 27E) (see below); distal haematodochal complex with balloon-like proximal portion (anchored by distal rim of tegulum) and sinuous, tapering embolic portion (anchored by flexible, hinged retro-ventral conductor) (Figs 26D, 27E). Unexpanded pedipalp with folded, wiry embolus abutting conductor (Fig. 17E); tegular sclerites embedded pro-distally (Fig. 20E); pedipalpal expansion and haematodochal inflation (e.g. see Figs 14E, 23E, 26D, 27E) resulting in significant conformational changes to shape of conductor, length and orientation of embolus, and relative position of tegular sclerites.

As noted by Wood (2008), the homology of the tegular sclerites among archaeid genera remains unclear, and this is especially true for Austrarchaea relative to Malagasy and African taxa. For the purposes of this revision, and for an easy comparison among species of Austrarchaea from mid-eastern Australia, the moveable tegular sclerites of the pedipalp are here numbered (1-3), relative to their pro-distal position within the unexpanded tegular cavity (e.g. see Figs 11F, 17F). Tegular sclerite 1 (TS 1) is a porrect, variably spiniform (Fig. 25F), rod-like (Fig. 20E) or filiform (Fig. 10F) process (breakable in some specimens; Fig. 21F) that originates near the prolateral base of the conductor, adjacent to the embedded base of the proximal embolic sclerite; during pedipalpal expansion this sclerite usually remains distally directed, positioned adjacent to the embolic haematodocha (Figs 26D, 27E). Tegular sclerite 2 (TS 2) is a distinctive, pointed, usually spur-like process, angled obliquely towards the conductor (Figs 11F, 25F), which is closely associated with the adjacent tegular sclerite 2a (TS 2a); in the unexpanded state, the sinuous, filiform TS 2a is usually obscured and ‘locked’ within a folded groove along the margin of TS 2 (see Forster and Platnick 1984, figs 60, 62). Tegular sclerite 3 (TS 3) is the most disto-dorsally positioned of the tegular sclerites, with a broader, more plate-like morphology relative to TS 1-2, usually visible as a distally pointed or rod-like projection beyond the retro-distal rim of the tegulum (Figs 14E-F, 17E-F, 20D-E).

Distribution.

Assassin spiders occur in mesic habitats throughout south-eastern, south-western and north-eastern mainland Australia (Fig. 2), usually in montane rainforests (Figs 30C, 38C, 41C) and wet eucalypt forests (Figs 39C, 42C, 45C), but occasionally in temperate heathlands or lowland rainforests (Fig. 40C). In south-eastern Australia they occur on Kangaroo Island (South Australia) and along the Great Dividing Range, from Grampians National Park in south-western Victoria north to Kroombit Tops National Park in south-eastern Queensland. In south-western Western Australia they occur from the Leeuwin-Naturaliste National Park east to Cape Le Grand National Park, with outlying populations in the Porongurup and Stirling Range National Parks. In north-eastern Queensland archaeids occur along the Great Dividing Range, from Eungella National Park near Mackay north to the Mount Finnigan Uplands, near Cooktown. Although this distribution is markedly concordant with the distribution of closed and tall open forests in Australia’s east and extreme south-west (see Specht 1981), assassin spiders appear to be notably absent from Tasmania, from the Australian Alps and from the 'St Lawrence Gap’ (Webb and Tracey 1981) (Fig. 2), as evidenced by the lack of museum specimens and despite targeted searches by the senior author.

Composition.

Five described species - Austrarchaea daviesae Forster & Platnick, 1984, Austrarchaea hickmani (Butler, 1929), Austrarchaea mainae Platnick, 1991b, Austrarchaea nodosa (Forster, 1956) and Austrarchaea robinsi Harvey, 2002a - and the 17 new species from mid-eastern Australia: Austrarchaea alani sp. n., Austrarchaea aleenae sp. n., Austrarchaea binfordae sp. n., Austrarchaea christopheri sp. n., Austrarchaea clyneae sp. n., Austrarchaea cunninghami sp. n., Austrarchaea dianneae sp. n., Austrarchaea harmsi sp. n., Austrarchaea helenae sp. n., Austrarchaea judyae sp. n., Austrarchaea mascordi sp. n., Austrarchaea mcguiganae sp. n., Austrarchaea milledgei sp. n., Austrarchaea monteithi sp. n., Austrarchaea platnickorum sp. n., Austrarchaea raveni sp. n. and Austrarchaea smithae sp. n.

Remarks.

At least three clades of Archaeidae can be recognised in Australia (Fig. 3B; see also Wood et al. 2010): a mid-eastern Australian clade, distributed from southern New South Wales to south-eastern Queensland (including the enigmatic, basal species Austrarchaea monteithi sp. n.); a north-eastern Queensland clade, endemic to tropical Queensland; and a southern Australian clade, known from Victoria, South Australia and south-western Western Australia. For the purposes of this revision, mid-eastern Australian species are diagnosed relative only to other related species from mid-eastern Australia (i.e. Austrarchaea nodosa and its closest relatives; Fig. 3B), all of which possess five or six dorsal hump-like tubercles on the abdomen (Figs 5F-G) and have a carapace height to carapace length (CH/CL) ratio ≥ 2.00. Austrarchaea daviesae and related species from north-eastern Queensland have only two pairs of hump-like tubercles on the abdomen (Fig. 5E), and Austrarchaea hickmani , Austrarchaea robinsi and Austrarchaea mainae from southern Australia have a carapace height to carapace length (CH/CL) ratio significantly less than 2.00 (M. Rix, pers. obs.).

Key to the species of Austrarchaea known from mid-eastern Australia (males required)