Ischnothyreus ogatai sp. nov.

[New Japanese Name: Ogata-Yoroi-Danigumo]

Figs. 8, 9

Heteroonops sp. Ono & Ogata 2018: p.41.

Type series. Holotype: female (NSMT-Ar 21921). Komi, Iriomote, Taketomi Town, Yaeyama District, 16-IV-2014, K. Ogata leg. Paratype: two females and one male (NSMT-Ar 21922). Same data as the holotype .

Etymology. The specific epithet and the new Japanese name are dedicated to late Mr. Kiyoto Ogata who was an enthusiastic amateur arachnologist and photographer and collected the specimens of this species.

Diagnosis. Ischnothyreus ogatai sp. nov. closely resembles I. an Tong et al., 2016 in having a pale-colored, less-developed sclerite on dorsum of abdomen (Figs. 8A, E, 9A, D), and finger-shaped sclerotized process on the base of the male fangs (Figs. 8I, 9G). However, it can be distinguished from I. an by the following characteristics: rounded tip of atrium (pointed in the latter species), an array of hairs arranged like semicircle on posterior margin of epigastric region (absent in I. an), edge of male clypeus lacking any projections (short and pointed, thorn-like protrusion in I. an), absence of sclerotized protrusion on basal part of anterior chelicerae in male (Figs. 8H, 9F; I. an possess thorn-like protrusion), and the shape of the male palp. Ischnothyreus ogatai sp. nov. possesses single ventral protuberance on the ventral side of palpal bulb and two moderately developed protrusions on the distal part of the palp (Figs. 8J–L, 9H–J). On the other hand, I. an has two ventral protuberances and a well-developed membranous leaf-shaped apophysis. Ischnothyreus ogatai sp. nov. also resembles I. tectorius Tong et al., 2016 in the general appearance, but can easily be distinguished by a scape-like sclerite on the anterior chelicerae, a large plate-like, strongly protruding extension on the edge of the clypeus, and absence of protrusion on the base of the male fangs. For further comparative details with East Asian species, see Tables 3 and 4.

Description.

Female (Holotype, NSMT-Ar 21921). Carapace oval, longer than wide, smooth and lacking projections. Endites wide and moderately rounded. Leg spiniation: femur I and II with two spines on prolateral side, tibia I and II with four pairs of spines on ventral side, metatarsus I with two pairs of spines on ventral side, femur II with a spine on prolateral side, leg III and IV spineless. Abdomen oval, weekly sclerotized scutum positioned on anterior dorsum, length of scutum shorter than half of abdomen length. Female genitalia (Figs. 8C, D, 9B, C). Atrium upside-down triangular shaped and positioned on the center of epigastric region, an array of hairs arranged like semicircle on posterior margin of epigastric region, with tip of hairs toward atrium; winding tube thick and simple, a pair of apodeme positioned on lateral side of epigastric region and running from anterior to posterior side. Coloration (Fig. 8A, B): carapace and abdomen reddish orange when alive (see figs of “ Heteroonopus sp.” in Ono & Ogata 2018), while turning to pale yellowish brown when preserved in ethanol. Chelicerae, maxilla, labium, sternum, palp and walking legs yellowish brown.

Measurements. BL 1.61, CL 0.72, CW 0.59, CH 0.31. Eye size: ALE 0.068, PME 0.060, PLE 0.064. Leg length: leg I, 0.56 + 0.23 + 0.44 + 0.32 + 0.18 = 1.73; leg II, 0.54 + 0.21 + 0.38 + 0.32 + 0.18 = 1.63; leg III, 0.46 + 0.20 + 0.30 + 0.13 + 0.17 = 1.26; leg IV, 0.65 + 0.30 + 0.39 + 0.27 + 0.18 = 1.79. AL 0.88, AW 0.71, AH 0.52.

Male (NSMT-Ar 21922). Carapace oval, longer than wide, smooth and lacking projections. Clypeus smooth and lacking projections on edge. Surface of chelicerae smooth and lacking projections. Finger-shaped sclerotized process attenuating from base of fangs. Endites narrower distally with pointed tip. Leg spiniation as well as female. Palp (Figs. 8J–L, 9H–J). Ventral protuberance on ventral side of palpal bulb and two moderately developed protrusions on the distal part of palp. Abdomen oval, weekly sclerotized scutum positioned on anterior dorsum, portion of scutum covering dorsum of abdomen larger than female. Coloration as well as female except palp dark brown.

Measurements. BL 1.31, CL 0.71, CW 0.58, CH 0.32. Eye size: ALE 0.070, PME 0.053, PLE 0.054. Leg length: leg I, 0.60 + 0.20 + 0.39 + 0.31 + 0.21 = 1.71; leg II, 0.45 + 0.18 + 0.39 + 0.29 + 0.19 = 1.50; leg III, 0.42 + 0.17 + 0.29 + 0.27 + 0.19 = 1.34; leg IV, 0.57 + 0.21 + 0.39 + 0.38 + 0.23 = 1.78. AL 0.59, AW 0.39, AH 0.44.

Distribution. Japan (Iriomote Island). Also see Fig. 11 and Table 2 for details of distribution in the Nansei Islands.

Habitat. This species was collected from litter layer of forests (Ono & Ogata 2018).