Dichodactylus, Okumura, 2017

Okumura, Ken-ichi, 2017, Dichodactylus gen. nov. (Araneae: Agelenidae: Coelotinae) from Japan, Species Diversity 22 (1), pp. 29-36 : 29-31

Genus Dichodactylus gen. nov.

Type species. Coelotes tarumii Arita, 1976

Diagnosis. Males of Dichodactylus can be clearly distinguished from males of all other coelotine genera except Orumcekia , some species of Platocoelotes and some species of Tegecoelotes by having two patellar apophyses and reduced LTA in male palp ( Figs 1B , 5 A–C). Females can be distinguished from all other coelotine genera except for some species of Coelotes , Draconarius Ovtchinnikov, 1999 and Pireneitega Kishida, 1955 by having anteroposteriorly elongated and convoluted spermathecae in an internal genitalia ( Figs 1D , 2D , 3D , 4D ). Males can be distinguished from males of Orumcekia by the absence of a ventral apophysis of the conductor and the semi-circular or crescent-shaped median apophysis ( Fig. 1A, B ) (vs. present, and spatulate or hook-shaped, respectively, in Orumcekia : Fig. 1E, F ; in an apparent simple labeling error in Wang (2002), median apophysis was marked as an embolus in figs 161, 162, however, it was correctly labeled elsewhere in the same paper, e.g., figs 166, 167); females are distinguished by the absence of a posterolaterally expanded margin in the epigynum ( Fig. 1C ) (vs. present in Orumcekia : Fig. 1G ). Moreover, females of Dichodactylus have anteroposteriorly elongated and convoluted spermathecae ( Fig. 1D ), while the spermathecae of Orumcekia are more compact and transversely oriented in the posterior portion of the vulva ( Fig. 1H ). Species of Dichodactylus can be distinguished from Platocoelotes by a spatulate conductor, short cymbial furrow, short embolus, and no epigynal hood ( Fig. 1 A–C) (vs. a conductor elongated to the base of cymbium obliquely, elongated cymbial furrow, long filiform embolus, and the presence of epigynal hood in Platocoelotes: Wang 2002, 2003 ). Specimens of Dichodactylus also can be distinguished from Tegecoelotes by a semi-circular or crescent-shaped median apophysis ( Fig. 1A, B ), no or nipple-shaped epigynal teeth ( Fig. 5 D–F) and anteroposteriorly elongated and convoluted spermathecae ( Fig. 1D ) (vs. hook-shaped median apophysis, broad epigynal teeth and posteriorly situated spermathecae in Tegecoelotes: Wang 2002, 2003 ).

Description. Small- to medium-sized coelotine spiders, 5.0–10.0 mm in length. Cheliceral promargin with three teeth, retromargin with four. Leg formula IV-I-II-III. Carapace brown or yellowish brown with grayish brown radial flecks; dorsum of abdomen grayish brown with yellowish brown chevrons or irregular spots, and venter yellowish brown with grayish brown irregular flecks; sternum yellowish brown and its marginal region brown; chelicerae and maxillae reddish brown; labium brown; legs yellowish brown with grayish brown ring flecks in femur, patella and tibia.

Male. Palp ( Figs 1A, B , 4 A–C): two patellar apophyses present; LTA reduced; RTA large and elongated; cymbial furrow short, one-sixth or one-seventh of the cymbial length; median apophysis crescent-shaped or semicircular; conductor spatulate, resembles that of Tegecoelotes .

Female. Epigynum and internal genitalia ( Figs 1C, D , 4 D–F): epigynum hexagonal or hourglass-shaped; epigynal teeth absent, or nipple-shaped and situated in posterior portion; epigynal hood absent; spermathecae elongated anteroposteriorly, convoluted and close to each other; spermathecal heads situated on anterolateral portion of spermathecae.

Composition. Three species:

1. Dichodactylus tarumii ( Arita, 1976) comb. nov.

2. Dichodactylus satoi ( Nishikawa, 2003) comb. nov.

3. Dichodactylus shinshuensis sp. nov.

Distribution. Japan (Chubu, Kinki and Chugoku Districts of Honshu, and Kyushu) ( Fig. 6 ).

Etymology. The generic name is a compound noun derived from the Greek prefix dicho-"paired", and dactylus- "finger" referring to having two patellar apophyses in the male palp. The gender is masculine.

Figures

Fig. 1. Comparison between the genera Dichodactylus gen. nov. and Orumcekia Koçak and Kemal, 2008: A–D, D. tarumii (Arita, 1974), male (A, B: NSMT-Ar 14732), and female (C, D: NSMT-Ar 14733); E–H, O. gemata (Wang, 1994), male (E, F: NSMT-Ar 14737), and female (G, H: NSMT-Ar 14736). A, E, ventral views of male palp; B, F, retrolateral views of male palp; C, G, ventral views of epigynum; D, H, dorsal views of internal female genitalia. Abbreviations: CON, conductor; CVA, conductor ventral apophysis; MA, median apophysis; PA, patellar apophyses; PEM, posterolaterally expanded margin; RTA, retrolateral tibial apophysis; SP, spermatheca.

Fig. 5. Comparison of genitalic characters of three species of Dichodactylus gen. nov. from Japan: A, D, D. shinshuensis sp. nov., male (A: NSMT-Ar 13339), and female (D: NSMT-Ar 13341); B, E, D. tarumii (Arita, 1976), male (B: NSMT-Ar 14732), and female (E: NSMT-Ar 14733); C, F, D. satoi (Nishikawa, 2003), male (C: NSMT-Ar 14735), and female (F: NSMT-Ar 14734). A–C, retrolateral views of male palp; D–F, ventral views of epigynum. Abbreviations: CO, conductor; ET, epigynal teeth; LAM, lamellas; PA, patellar apophyses; SW, swollen portion of tegulum. Black circle on tibia shows the vestigial LTA.

Fig. 2. Dichodactylus shinshuensis sp. nov., male (A, B: holotype, NSMT-Ar 13339), female (C, D: paratype, NSMT-Ar 13341). A, ventral view of male palp; B, retrolateral view of male palp; C, ventral view of epigynum; D, dorsal view of internal female genitalia. Abbreviations: CD, copulatory duct; CO, conductor; CY, cymbial furrow; EM, embolus; LAM, lamellas; MA, median apophysis; PA, patellar apophyses; RTA, retrolateral tibial apophysis; SP, spermatheca. Scale bars: 0.5mm.

Fig. 3. Dichodactylus tarumii (Arita, 1976). male (A, B: NSMT-Ar 14732), female (C, D: NSMT-Ar 14733). A, ventral view of male palp; B, retrolateral view of male palp; C, ventral view of epigynum; D, dorsal view of internal female genitalia. Abbreviations: CO, conductor; CY, cymbial furrow; EM, embolus; ET, epigynal teeth; MA, median apophysis; PA, patellar apophyses; RTA, retrolateral tibial apophysis; SP, spermatheca; SH, spermathecal head. Scale bars: 0.5mm.

Fig. 4. Dichodactylus satoi (Nishikawa, 2003). male (A, B: NSMT-Ar 14735), female (C, D: NSMT-Ar 14734). A, ventral view of male palp; B, retrolateral view of male palp; C, ventral view of epigynum; D, dorsal view of internal female genitalia. Abbreviations: CO, conductor; CY, cymbial furrow; EM, embolus; MA, median apophysis; PA, patellar apophyses; RTA, retrolateral tibial apophysis; SP, spermatheca; SH, spermathecal head. Scale bars: 0.5mm.

Fig. 6. Distribution of three species of the genus Dichodactylus gen. nov. from Japan. Closed circles denote D. shinshuensis sp. nov.; closed inverted triangles, D. tarumii (Arita, 1976); crosses, D. satoi (Nishikawa, 2003).