Oedothorax, Lin & Lopardo & Uhl, 2022

Lin, Shou-Wang, Lopardo, Lara & Uhl, Gabriele, 2022, Evolution of nuptial-gift-related male prosomal structures: taxonomic revision and cladistic analysis of the genus Oedothorax (Araneae: Linyphiidae: Erigoninae), Zoological Journal of the Linnean Society 195, pp. 417-584 : 426-428

OEDOTHORAX S.S. BERTKAU, 1883

Type species: Neriene gibbosa Blackwall, 1841 .

Monophyly: This group is supported by the following unambiguous character transformations: paracymbium base visible from dorsal view of male pedipalp (Ch 4, homoplastic), median position of distal setae group on paracymbium (Ch 7, synapomorphic), embolus base horn present (Ch 12, synapomorphic) embolic membrane cylindrical (Ch 34, synapomorphic) and tegular papillae present (Ch 42, homoplastic); and the following ambiguous character transformations: embolus prolaterally spiral (Ch 11, homoplastic, ambiguous transformation), radix – embolus membranous region extend to prolateral side of radix (Ch 24, synapomorphic, ambiguous transformation).

Diagnosis: The newly circumscribed Oedothorax s.s. is similar to Callitrichia , Mitrager and other species in Clade 13 in their configuration of the embolic division, the tibial chaetotaxy and the epigyne morphology. Oedothorax s.s. is characterized and can be distinguished from other taxa in Clade 13 by the following features:

1. Paracymbium: small-sized; base visible from dorsal view of male pedipalp (medium- to large-sized in other species in Clade 13; base covered by cymbium from dorsal view); distal part not enlarged (greatly enlarged in most Callitrichia species); distal setae group with middle position or indistinguishable from basal setae group (with distal position in other species in Clade 13); distal clasp distally extended, without striae (retrolaterally extended and/or with striae in many Mitrager species).

2. Copulatory bulb: embolus base protuberance present (arrow in Fig. 5B ) (absent in other species in Clade 13); embolus prolaterally spiral around pointed, prolaterally spiral anterior radical process (embolus retrolaterally spiral in other species in Clade 13); embolic membrane cylindrical (imperceptible in some species in unexpanded pedipalps) (either flat and broad or absent in other species in Clade 13); embolus–radix membranous region extended to prolateral side of radix (not extended to prolateral side of radix in other species in Clade 13); ventral radical process absent (present in most Callitrichia , some Mitrager , Atypena and some ‘ Oedothorax ’ incertae sedis species); lateral extension of radix absent (present in all Mitrager , Atypena , Ca. convector and some ‘ Oedothorax ’ incertae sedis species); tegular papillae present in some species, protegulum with papillae, tegular sac short; marginal suprategular apophysis present; distal suprategular apophysis straight, distally oriented, mostly narrow and round at tip (except Oe. gibbosus and Oe. trilobatus , tip broad and smoothly serrated). 3. Tibia: moderately modified; shape of prolateral apophysis varies among species, but never elevated vertically (vertically elevated in many Callitrichia , some Mitrager and some ‘ Oedothorax ’ incertae sedis species); with basal thorn in some species (absent in other species in Clade 13); retrolateral apophysis absent (present in Mitrager , Atypena , Ca. convector and some ‘ Oedothorax ’ incertae sedis species); prolateral spike absent (present in most Mitrager species).

4. Epigyne: different from Callitrichia and Holmelgonia in the mesal entrance of copulatory ducts into the spermathecae with respect to the exits of the fertilization ducts.

Description: The genus includes medium-sized (male 1.2–2.5, female 2.1–3.8) erigonines with an evenly coloured opisthosoma from light brown to dark brown. Male and female posterior median spinnerets with one minor ampullate gland spigot, two aciniform gland spigots; posterior lateral spinnerets with triad, more than three aciniform gland spigots; female posterior median spinnerets and posterior lateral spinnerets with one and two cylindrical gland spigots, respectively. Male prosoma varies in the degree of prosomal modifications, ranging from unnoticeable (Oe. paludigena, Oe. agrestis, Oe. fuscus and Oe. tingitanus ) to prominent post-PME humps, post-PME grooves and lateral sulci and pits. Palpal patella prolateral proximal vertical macrosetae absent.This genus also shares those features defining Clade 13 (see above). For palpal and epigynal features, see description of Clade 13 and diagnosis.

New circumscription: According to our phylogenetic analysis and descriptions from the literature, only ten species are regarded here as ‘true’ Oedothorax: Oe. gibbosus and its congeners: agrestis , apicatus , fuscus , gibbifer , meridionalis , paludigena , retusus , tingitanus and trilobatus . However, 27 additional species remain here as ‘ Oedothorax ’ incertae sedis (see section below) and are deemed not congeneric with the type species, but await future taxonomic treatment. The remaining 43 species are transferred from Oedothorax to other genera (see taxonomic actions below).

Natural history: Most species are found in humid environments like in litter, under bark or stones, in grasslands, marshes or at riversides.

Remarks: Although no types of Oedothorax s.s. were examined, detailed descriptions and illustrations in the literature abound, allowing clear identification of the examined specimens.

New distribution: Europe, Turkey, Caucasus, Iran, Russia to Central Asia, China, Azores, North Africa, North America.

Figures

Figure 5. Oedothorax agrestis (Blackwall, 1853). A–D, male left palp. A, retrolateral view. B, prolateral view. C, dorsal view. D, ventral view. E–H, epigyne. E, ventral view. F, dorsal view. G, anterior view. H, external morphology. Scale bar 0.1 mm.