Erigomicronus, Tanasevitch, 2018

Tanasevitch, Andrei V., 2018, A new, remarkable erigonine spider genus from eastern Asia (Araneae, Linyphiidae), Zootaxa 4524 (2), pp. 245-250 : 246-247

Erigomicronus new genus

Type species: Oreonetides longembolus Wunderlich & Li, 1995 .

Diagnosis. Very small (1.10–1.35) pale colored spiders. Males are diagnosed by the following combination of the characters: strongly modified paracymbium, devoid pockets and carrying several untypical outgrowths (see Figs 1, 5 ; Marusik et al. 2016: figs 14, 15); presence of a special ventral outgrowth on the distal suprategular apophysis, which performs the role of a column, designated herewith as a column-like process; and a very complicated embolic division, notably, large and highly modified radix, whip-shaped embolus and presence of a highly developed convector ( Figs 3, 4 ). Females are diagnosed by the presence of a scape-like projection in the epigynum, which devoid the copulatory ducts (or entrance grooves).

N.B. The generic diagnosis and description are mainly based on the conformation of the secondary genitalia of O. longembolus , so as to avoid damage to the type specimens of Maro lautus Saito, 1984 loaned from NSMT.

The structure of the embolic division in Erigomicronus new genus resembles that of the erigonine genus Houshenzinus Tanasevitch, 2006 , whose members are also characterized by a highly developed convector, the sclerite that protects and supports the whip-shaped embolus (please refer to figures where these structures can be seen) (see Tanasevitch 2006: figs 45, 46; Zhao & Li 2014: fig. 45B). The new genus differs from Houshenzinus by the absence of a trichobothrium on metatarsi IV, by the strongly modified paracymbium, which devoid pockets and carrying several untypical outgrowths, by the presence the column-like process on the distal suprategular apophysis, as well as by the presence of the scape-like projection in the epigynum and by the straight copulatory ducts (vs. helical) (cp. Figs 6, 8 and Song & Li 2008: fig. 27; Zhao & Li 2014: fig. 46C).

Etymology. The generic name is consonant with the names of two subfamilies, i.e., Erigoninae and Micronetinae . The gender of the genus name is masculine.

Description. Total length 1.10–1.35. Very small, pale spiders. Carapace unmodified, eyes slightly enlarged. Chaetotaxy 2.2.2.1, lateral tibial spines absent; metatarsi unarmed. Metatarsi I-III each with a trichobothrium. TmI 0.30–0.40. Palpal tibia simple, without apophyses. Paracymbium highly modified, its median part extending into a long, thick, rounded outgrowth ( Figs 1, 5 ). Distal suprategular apophysis with a “pit-hook”-like process anteriorly ( Figs 1, 2, 5 ). Column-like process of DSA sclerotized, flexible connected to radix, carrying inside a duct that enters directly into the radix ( Fig. 4 ). Median membrane large, wide, hardly discernible among poorly sclerotized and highly curved parts of embolic division. Embolic division very complicated: radix well-developed, flat, curved and connected to a large and complex convector, the latter surrounding in part a long, whip-like embolus ( Figs 4, 5 ). In retrolateral view, convector resembling a micronetine’ lamella characteristica ( Figs 3, 5 ), with which it was confused in the original description of both Oreonetides longembolus and Maro lautus (see Saito 1984, Wunderlich & Li 1995).

Epigynum somewhat protruded, anterior wall extended and overhanging above epigynal cavity ( Figs 6, 7 ). Anterior wall with a scapus-like projection lacking copulatory ducts and bearing a large pit anteriorly ( Fig. 9 ). Posterior median plate present (vs. Marusik et al. 2016), triangular, weakly sclerotized and slightly sunken compared to surrounding edges of lateral walls ( Fig. 8 ). Copulatory ducts starting at base of scapus-like projection, then jointly running along center of anterior wall towards end of the projection; thereafter diverging to proceed separately along edge of lateral walls towards subspherical receptacula ( Fig. 8 ).

Species included. Erigomicronus longembolus ( Wunderlich & Li, 1995) new combination, and E. lautus ( Saito, 1984) new combination.

Distribution. Russian Far East, eastern China, Japan.

Phylogenetic placement. Based on the male palp morphology, namely, the presence of a long, whip-like embolus, the flat, strongly curved and not boat-saped radix, the absence of the Fickert’s gland, as well as the presence of a convector, Erigomicronus new genus cannot be placed amongst the subfamily Micronetinae sensu Saaristo & Tanasevitch (1996) and it seems better to be allocated to the subfamily Erigoninae . The subfamily Micronetinae sensu Saaristo & Tanasevitch (1996) has recently been suggested as not a natural group, but paraphyletic with respect to monophyletic Erigoninae ( Arnedo et al. 2009) and treated as “micronetine line within the clade proposed by authors (op. cit.) that includes the “micronetines” and Erigoninae ( Tu & Hormiga 2010) .

Figures

FIGURES 1–5. Erigomicronus longembolus (Wunderlich & Li, 1995) n. comb., male from Vladivostok, Russia (1–4) and E. lautus (Saito, 1984) n. comb., male paratype (NSMT, Art. 858) (5). 1, 5, palp, retrolateral view; 2, distal suprategular apophysis and median membrane; 3, 4, embolic division and distal suprategular apophysis, different aspects. Scale bars, 0.1 mm.

FIGURES 6–10. Erigomicronus longembolus (Wunderlich & Li, 1995) n. comb., from Vladivostok, Russia (6–9) and E. lautus (Saito, 1984) n. comb., female paratype (NSMT, Art. 858) (10). 6–8, epigynum, dorsal, lateral, dorsolateral views, respectively; 10, epigynum ventral view. Scale bar, 0.1 mm.