Psechrus omistes, sp. nov.
Creators: name: Bayer, Steffen
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Psechridae
Psechrus
Psechrus omistes

description: Psechrus omistes sp. nov.
Figs 18, 27 A,D, 35
Type material. Holotype ♂ (SB 1221): INDONESIA: Sumatra: Lampung Prov.: Bukit Barisan Selatan National Park, road Krui to Liwa, 2 km SW of Kubuprahu, 480–540 m, ca. 05°05'S, 104°01'E, disturbed evergreen rain forest and secondary forest, P. Schwendinger leg. 04.III.2000, sample number: Sum-00/25, MHNG.
Etymology. The specific name refers to the conspicuous and partly sclerotised conductor base of the male palp, which looks like a bearer for the membranous, distal part of the conductor (Ancient Greek “ omistes ” means “porter” or “bearer”); term (noun) in apposition.
Diagnosis. Males distinguished from those of all other Psechrus species by: (1) The characteristic conductor base, which is long (more than half the length of tegulum), relatively broad (width 1/3 of its length) and exhibits a conspicuously dark and sclerotised ventral surface with many small striae and wrinkles (Figs 18 A–B, 27A), but without small spines or tubercles; (2) the massive embolus with a voluminous base and a roughly sickle-shaped distal section (Figs 18 B–C, 27D).
Description. Male: Body and eye measurements: Carapace length 4.1, maximal carapace width 2.9, anterior width of carapace 1.3, opisthosoma length 6.4, opisthosoma width 1.8. Eyes: AME 0.25, ALE 0.29, PME 0.29, PLE 0.29, AME–AME 0.14, AME–ALE 0.07, PME–PME 0.17, PME–PLE 0.23, AME–PME 0.38, ALE–PLE 0.32, clypeus height at AME 0.62, clypeus height at ALE 0.47.
Cheliceral furrow with three promarginal and four retromarginal teeth.
Spination: Palp: 131, 110 (prolateral one less than half as long as dorsal one), 1101 (all spines ca. half as long and broad as those on femur); legs: femur I 746, II 646, III–IV 545; patella I–IV 000; tibia I–II 3036, III 3133, IV 3133{3123}; metatarsus I–III 3035, IV 3035{3034}.
Measurements of palp and legs: Palp 5.2 [1.8, 0.8, 0.7, 1.9], I 61.4 [16.2, 1.9, 17.0, 18.2, 8.1], II 44.2 [11.5, 1.6, 11.6, 13.1, 6.4], III 28.4 [8.1, 1.2, 7.4, 8.4, 4.3], IV 48.4 [13.1, 1.2, 12.1, 14.6, 7.4]. Leg formula: 1423. FEMI+MTT-I/CL=8.39, thus legs (in relation to carapace length) conspicuously long, longer than in all other Psechrus species.
Palpal femur ventrally with small and inconspicuous modification (Fig. 18 D) in form of a flat bulge proximally. Macrosetae ventrally on coxae of leg I present in form of an apical row (the same on trochanter of leg I & II).
Copulatory organ: Cymbium relatively long and with dense dorsal scopula, which covers 1/3 of cymbium (Fig. 27 D); tegulum less than 1.5 times longer than broad (Figs 18 B, 27A) and with flat and inconspicuous bulge basoretrolaterally (Fig. 18 B); conductor with light and fleshy retro- and prolateral sections, membranous and complicatedly folded distal section (Figs 18 A–C) and arising in an 11:00 o’clock position on tegulum; embolus with voluminous base exhibiting a ventral extension (Figs 18 B–C), distal part with some ridges dorsally, distal tip distinctly narrower than subdistal section; sperm duct v-shaped but prolateral distal curve in prolatero-distal section of tegulum recognisable in ventral view; subtegulum in ventral view hardly protruding underneath tegulum (Fig. 18 B), visible in prolateral view, but only a little part of it (Fig. 18 A).
Female: unknown.
Colouration (see also description for Psechrus in Bayer 2012): Median bands on carapace not serrated, lateral bands hardly serrated and, if compared with other Psechrus species, relatively broad (broadest section ca. 2 diameter of PME). Light longitudinal line ventrally on opisthosoma very narrow and continuous. If measured centrally on opisthosoma, its width is only ca. 0.25 of one half of the cribellum.
Taxonomic remarks. One Psechrus species from Sumatra, P. arcuatus Bayer, 2012, is solely known by females. It is very unlikely that the male holotype of Psechrus omistes sp. nov. is conspecific with P. arcuatus, because the type locality of the latter is ca. 670 km further north-north-west from the region of the Barisan Selatan National Park, the type locality of Psechrus omistes sp. nov.. The great majority of Psechrus species have distribution areas that are smaller or far smaller than 600 km in diameter. Moreover, in relation to the long copulatory duct of P. arcuatus (Bayer 2012, fig. 20b) one would rather expect a conspecific male with a longer and narrower embolus than that of P. o m i s t e s sp. nov..
Distribution. Indonesia (Sumatra) (Fig. 35).
description: Published as part of Bayer, Steffen, 2014, Seven new species of Psechrus and additional taxonomic contributions to the knowledge of the spider family Psechridae (Araneae), pp. 1-54 in Zootaxa 3826 (1) on pages 31-33, DOI: 10.11646/zootaxa.3826.1.1, http://zenodo.org/record/286429