Micropholcomma Crosby & Bishop, 1927

Rix, Michael & Harvey, Mark, 2010, The spider family Micropholcommatidae (Arachnida: Araneae: Araneoidea): a relimitation and revision at the generic level, ZooKeys 36 (36), pp. 1-321 : 23-24

Genus Micropholcomma Crosby & Bishop, 1927

Micropholcomma Crosby & Bishop, 1927: 152 . Type species by original designation Micropholcomma caeligenus Crosby & Bishop, 1927 . Roewer, 1942: 392. Hickman, 1944: 183. Bonnet, 1957: 2905. Forster, 1959: 297. Hickman, 1981: 65. Brignoli, 1983: 374. Rix, 2008: 343. Platnick, 2009.

Microlinypheus Butler, 1932: 103 . Type species by monotypy Microlinypheus bryophilus Butler, 1932 . Roewer, 1942: 617. Synonymised by Hickman, 1944: 186. Bonnet, 1957: 2885.

Plectochetos Butler, 1932: 106 . Type species by monotypy Plectochetos longissimus Butler, 1932 . Roewer, 1942: 617. Bonnet, 1958: 3707. Synonymised by Forster, 1959: 297.

Affinities. The genus Micropholcomma appears to be the sister-lineage to Pua novaezealandiae from New Zealand ( Fig. 4 ).

Diagnosis. Species of Micropholcomma can be distinguished from all other Micropholcommatini except Pua novaezealandiae by the presence of a normal, non-bifurcate embolus ( Fig. 9A ); and can be distinguished from Pua by the presence of a long embolus (length> 5× width) which is usually looped or coiled ( Figs 9A , 12A, 17B). Other diagnostic characters include the presence (and presumed retention) of posterior tracheae (shared with Gigiella ) and the presence of a male leg I-pedipalpal stridulatory system (Fig. 21D).

Description. Very small, entelegyne Araneoidea ; total length 0.70 to 1.30. Cephalothorax: Carapace without glandular depressions above maxillae; cuticle without glandular pits (Fig. 18C); margins fused to sternum via pleural sclerites. Eight (Fig. 18C), rarely six or (in troglomorphic taxa) fewer eyes present on anterior margin of pars cephalica; AME, if present, smallest. Chelicerae with or without bulging anterior projections in males; promargin with true teeth, a pair of fused setal sockets adjacent to base of fang and single peg tooth in males (Fig. 19F).

Legs and female pedipalp: Legs three-clawed ( Fig. 20D ), covered with smooth or serrate hair-like setae; femur I of males with prolateral stridulatory denticles (Fig. 18C). Trichobothria present on legs; tibiae each with two or three trichobothria ( Fig. 20C ); metatarsi without trichobothria. Female pedipalp four-segmented (with fused tibiatarsus) or reduced to a vestigial nubbin; claw absent (Figs 19C–D).

Abdomen: Abdomen oval or globose; anterior sclerite present around epigastric region and petiole; large dorsal scute present on males (Fig. 14), absent (Fig. 16B) or (rarely) present (Fig. 13B) on females; lateral sclerotic strips present on males; posterior sclerotic ring surrounding spinnerets and colulus. Six spinnerets situated posterior to fleshy colulus ( Figs 22A, 22C , 23 A–B); PMS of M. bryophilum with single medial AC gland spigot; PLS of M. bryophilum with complete triad. Anterior tracheal system welldeveloped, with relatively large lateral atria and multiple radiating tracheae (Fig. 15B); second tracheal tubes on each side looping mesally and extending through petiole into cephalothorax (Fig. 12D); posterior tracheal spiracle present, tracheae quadritracheate.

Genitalia: Male pedipalp (Fig. 21) small to large, relatively simple; patella with distally-directed, flanged or hooked ligulate retrolateral apophysis and retrolateral stridulatory ridges; tegulum smooth, with curved evaginated tegular ridge; embolus exposed, long (length> 5× width), usually looped or coiled. Female genitalia (Figs 15A–E) with pair of separate, globular anterior spermathecae; insemination ducts coiled around fertilisation ducts; fertilisation ducts posteriorly-directed.

Distribution. Eastern and western mainland Australia and Tasmania (Fig. 217). Two undescribed female specimens from Rivière Bleue and Mont Mou, New Caledonia (QMB S60522 , QMB S72474) probably also belong in this genus, but males are required to confirm the identification.

Composition. Seven described species, Micropholcomma bryophilum ( Butler, 1932) , M. caeligenum Crosby & Bishop, 1927 , M. linnaei Rix, 2008 , M. longissimum ( Butler, 1932) , M. mirum Hickman, 1944 , M. parmatum Hickman, 1944 , M. turbans Hickman, 1981 , and the new species M. junee . Undescribed species are also known from throughout the range of the genus.

Nomenclatural remarks. The gender of the genus name “ Micropholcomma ” was not specified by Crosby and Bishop (1927), although the type species was described with a masculine specific epithet (as M. “ caeligenus ”). The name Micropholcomma was clearly derived from the theridiid taxon name “ Pholcomma ” Thorell, and as highlighted by Levi (1964), this name should be treated as neuter. To this end, Brignoli (1983) and Davies (1985) amended the suffix endings of the species names, all of which were previously masculine or feminine.

Figures

Figure 4. Optimal cladogram for the Micropholcommatidae under equal and implied weights, and one of six equally parsimonious trees recovered from an equal weights analysis of the ‘new’ matrix (length = 135; see Appendix II). With the exception of the highlighted (*) node ‘Patelliella adusta + Micropholcommatini’, all clades shown were recovered in all iterations of an implied weights analysis (K=1–6); the phylogenetic position of P. adusta changed to ‘P. adusta + Textricellini’ under K-values 1–5. Unambiguous character optimisations are shown for each node, and bold species are newly described, with generic type species highlighted (*).

Figure 9. Left pedipalps of male Micropholcommatini, Textricellini and Taphiassinae, showing trajectory of the sperm ducts: A Micropholcomma caeligenum Crosby & Bishop B Tinytrella pusilla (Forster) C Taphiassa punctata (Forster). Scale bars = 0.065 mm (65 µm). Numbered arrows denote the trajectory of the ducts, from the subtegular fundibule (1) to the base of the embolus.

Figure 20. Scanning electron micrographs of female Micropholcomma bryophilum (Butler) from near Marysville, Victoria (WAM T94453): A leg I tarsal organ B leg I lyriform organ C leg I tibial trichobothrium D leg IV claws, showing elongate inferior claw.

Figure 22. Scanning electron micrographs of spinnerets of female Micropholcomma bryophilum (Butler) from near Marysville, Victoria (WAM T94453) (left) and paratype female Austropholcomma florentine sp. n. from the Florentine Valley, Tasmania (FMC) (right): A–B anterior lateral spinnerets C–D posterior lateral spinnerets. Arrows denote the anterior, mesal direction.

Figure 23. Scanning electron micrographs of posterior median spinnerets of female (left) and male (right) Micropholcommatini: A–B Micropholcomma bryophilum (Butler) from near Marysville, Victoria (WAM T94453) C–D Pua novaezealandiae Forster from the Makarora Valley, New Zealand (AMNH) E–F Austropholcomma florentine sp. n. from the Florentine Valley, Tasmania (FMC) G–H Tricellina gertschi (Forster & Platnick) from near Chaitén, Chile (AMNH). Note the apparent loss of the anterior CY gland spigot in female Austropholcomma and Tricellina. Arrows denote the anterior, mesal direction.