Male (holotype) (in mm). Body: habitus as in Fig. 1A, C and E; body length 1.75. Carapace (Fig. 1B and E): 0.85 long, 0.67 wide; yellow, with faint egg-shaped patches behind eyes, ovoid in dorsal view, profile dome-shaped, pars cephalica smooth, pars thoracica finely reticulate. Clypeus (Fig. 1F): rounded, slightly protruding, height about 1.45 times ALE diameter. Eyes (Fig. 1B and F): six, well developed, ALE largest, PME smallest, posterior eye row straight from above, procurved from front. Sternum (Fig. 1D): pale yellow, as long as wide. Mouthparts (Fig. 1D and G–I, Fig. 2I and M): chelicerae, endites and labium orange; chelicerae short, with large base, almost as wide as long, slightly recessed, fang with a flag-shaped process on proximal 1/3 and a small sclerotised process basally, fang groove with one large and a few small denticles; labium rounded, with sclerotised lateral margins; endites stout, anteromedian tip of endites with one strong, tooth-like projection. Abdomen: 0.91 long, 0.63 wide; dorsal scutum pale orange, oval, well sclerotised, covering 1/2 of abdomen width and approximately 3/5 of abdomen length, unfused to epigastric scutum; epigastric and postgastric scutum well sclerotised, pale orange, fused, postgastric scutum covering about 3/5 of abdomen length; spinneret scutum present, incomplete ring. Legs: pale orange, femur I with 2 prolateral spines, tibia I with 4 pairs, metatarsus I with 2 pairs of long ventral spines. Leg II spination similar to leg I, except femur with only 1 prolateral spine. Legs III and IV spineless. Sperm pore large, round, situated in front of anterior spiracles. Palp (Fig. 2A–H and J–L): trochanter with ventral projection; femur normal size; patella about as long as femur, not enlarged; tibia with three trichobothria; cymbium fused with bulb; bulb simple, without distinct ventral protuberance, distal end elongated, with a sharp tooth-like extension, with a small dorsal protuberance and a broad, rectangular-shaped retrolateral lobe.

Figure 1.  

Ischnothyreus yunlong sp. n., holotype male. A. habitus, dorsal view; B. prosoma, dorsal view; C. habitus, ventral view; D. prosoma, ventral view; E. habitus, lateral view; F. prosoma, anterior view; G. left chelicerae, anterior view; H. left chelicerae, lateral view; I. left chelicerae, posterior view. Abbreviations: fp = flag-shaped process, ssp = small sclerotised process, stp = strong, tooth-like projection. Scale bars: 0.4 (A–F) and 0.05 (G–I).

Figure 2.  

Ischnothyreus yunlong sp. n., holotype male, light (A–C) and SEM (D–M) microphotographs A. left palp, prolateral view; B. left palp, dorsal view; C. left palp, retrolateral view; D. left palp, prolateral view; E. left palp, retrolateral view; F. distal part of palpal bulb, dorsal view; G. palpal bulb, prolateral view; H. palpal bulb, retrolateral view; I. left chelicerae, anterior view; J. distal part of palpal bulb, prolateral view; K. distal part of palpal bulb, retrolateral view; L. palpal bulb, dorsal view; M. left chelicerae, posterior view. Abbreviations: dp = dorsal protuberance, fp = flag-shaped process, rl = retrolateral lobe, ssp = small sclerotised process, ste = sharp, tooth-like extension, vp = ventral projection. Scale bars: 0.1 (A–E, G, H), 0.05 (I, L, M) and 0.02 (F, J, K).

Female (SYNU-475) (in mm): same as male, except as noted. Body: habitus as in Fig. 3A, C and E; body length 1.88. Carapace: 0.82 long, 0.68 wide, profile elevated. Clypeus lower, not protruding. Mouthparts: chelicerae unmodified; endite with serrula. Abdomen: 1.16 long, 0.77 wide; dorsal scutum covering 1/3 of abdomen length, about 1/4 of abdomen width. Epigastric area (Fig. 3H and I): surface without external features. Endogyne (Fig. 3J): from middle of slightly thickened margin of postgastric scutum runs a dark, tight complex winding tube, ending in a large bell-shaped sclerotised extension; posteriorly directed apodemes present.

Figure 3.  

Ischnothyreus yunlong sp. n., paratype female A. habitus, dorsal view; B. prosoma, dorsal view; C. habitus, ventral view; D. prosoma, ventral view; E. habitus, lateral view; F. prosoma, lateral view; G. prosoma, anterior view; H. epigastric region, ventral view; I. endogyne, ventral view; J. endogyne, dorsal view. Abbreviations: a = apodemes, bse = bell-shaped sclerotised extension, wt = winding tube. Scale bars: 0.4 (A–F), 0.2 (G, H) and 0.1 (I, J).

Figure 4.  

Ischnothyreus yueluensis Yin & Wang, 1984, male (SYNU-450) A. habitus, dorsal view; B. prosoma, dorsal view; C. habitus, ventral view; D. prosoma, ventral view; E. habitus, lateral view; F. prosoma, anterior view; G. left chelicerae, anterior view; H. left chelicerae, lateral view; I. left chelicerae, posterior view. Abbreviations: sp = stick-shaped process, stp = strong, tooth-like projection. Scale bars: 0.4 (A–F) and 0.05 (G–I).

Figure 5.  

Ischnothyreus yueluensis Yin & Wang, 1984, male (SYNU-450), light (A–C) and SEM (D–L) microphotographs. A. left palp, prolateral view; B. left palp, dorsal view; C. left palp, retrolateral view; D. left palp, prolateral view; E. left palp, retrolateral view; F. left palp, dorsal view; G. palpal bulb, prolateral view; H. palpal bulb, retrolateral view; I. distal part of palpal bulb, dorsal view; J. distal part of palpal bulb, prolateral view; K. distal part of palpal bulb, retrolateral view; L. left chelicerae, posterior view. Abbreviations: dlm = dorsal leaf-shaped membrane, pl = prolateral lobe, plm = prolateral leaf-shaped membrane, rl = retrolateral lobe, sp = stick-shaped sclerotised process, vp = ventral projection, vpr = ventral protuberances. Scale bars: 0.1 (A–F), 0.05 (G, H) and 0.02 (I–L).

Figure 6.  

Ischnothyreus yueluensis Yin & Wang, 1984, female (SYNU-452) A. habitus, dorsal view; B. prosoma, dorsal view; C. habitus, ventral view; D. habitus, lateral view; E. prosoma, ventral view; F. epigastric region, ventral view; G. prosoma, anterior view; H. endogyne, ventral view; I. endogyne, dorsal view. Abbreviations: a = apodemes, bse = bowl-shaped sclerotised extension, wt = winding tube. Scale bars: 0.4 (A–E, G), 0.2 (F) and 0.1 (H, I).

The new species is similar to Ischnothyreus bauri Richard, 2016 (female unknown) in the large retrolateral lobe of the palpal bulb, but can be distinguished by the absence of the ventral protuberance (Fig. 2G and H) of the palpal bulb (vs. two ventral protuberances (Richard et al. 2016: figs. 5A and B)) and the flag-shaped process (Fig. 2I and M) on proximal 1/3 of the male chelicerae fang and the small sclerotised process of fang base (vs. strongly thickened on proximal 2/3 and unmodified fang base (Richard et al. 2016: figs. 6A, B and C)). Females of the new species are similar to Ischnothyreus campanaceus Tong & Li, 2008, but can be distinguished by the small abdominal dorsal scutum (covering 1/3 of the abdomen length (Fig. 3A) vs. nearly 5/6 of the abdomen length (Tong 2013: fig. 44B)).

The specific name is a noun in apposition from the type locality.

Known only from the type locality (Fig. 7).

Figure 7.  

Distribution of two Ischnothyreus species from China. 1. I. yunlong sp. n. 2. I. yueluensis Yin & Wang, 1984.

Male (SYNU-450) (in mm). Body: habitus as in Fig. 4A, C and E; body length 1.45. Carapace (Fig. 4B, E and F): 0.76 long, 0.56 wide; brown, with egg-shaped patches behind eyes, ovoid in dorsal view, profile elevated, surface of elevated portion of pars cephalica smooth, sides strongly reticulate, lateral margins straight, smooth. Clypeus (Fig. 4F): rounded, slightly protruding, height about 0.80 times of ALE diameter. Eyes (Fig. 4B and F): six, well developed, ALE largest, PLE smallest, posterior eye row straight from above, procurved from front. Sternum (Fig. 4D): pale orange, longer than wide. Mouthparts (Fig. 4D and G–I; Fig. 5L): chelicerae, endites and labium orange; chelicerae straight, base of fangs with small stick-shaped sclerotised process, fang groove with field of small denticles; anteromedian tip of endites with one strong, tooth-like projection. Abdomen: 0.75 long, 0.46 wide; dorsal scutum well sclerotised, pale orange, covering 4/5 of abdomen width and approximately 5/6 of abdomen length, unfused to epigastric scutum; epigastric and postgastric scutum well sclerotized, pale orange, fused, postgastric scutum covering about 2/3 of abdomen length. Legs: pale orange, femur I with 2 prolateral spines, tibia I with 4 pairs, metatarsus I with 2 pairs of long ventral spines. Leg II spination similar to leg I, except femur with only 1 prolateral spine. Legs III and IV spineless. Sperm pore large, oval, situated at level of anterior spiracles. Palp (Fig. 5A–K): trochanter with ventral projection; femur normal size; patella about as long as femur, not enlarged; tibia with three trichobothria; cymbium fused with bulb; bulb with 2 ventral protuberances, one large and another very small, distal end elongated, with a prolateral lobe and several leaf-shaped membranes, retrolateral lobe small.

Female (SYNU-452) (in mm): same as male, except as noted. Body: habitus as in Fig. 6A, C and D; body length 1.49. Carapace: 0.67 long, 0.53 wide. Mouthparts: chelicerae and endites unmodified. Abdomen: 0.84 long, 0.58 wide; dorsal scutum covering 1/2 of abdomen length, about 3/4 of abdomen width. Epigastric area: surface without external features. Endogyne (Fig. 6I): from middle of slightly thickened margin of postgastric scutum runs a dark, simple winding tube, ending in a small, narrow bowl-shaped sclerotised entension; posteriorly directed apodemes present.

This species is similar to Ischnothyreus concavus Richard, 2016 in the stick-shaped sclerotized process on the male fang base, but can be distinguished by the prolateral lobe (Fig. 5I) of palpal bulb, which is lacking in Ischnothyreus concavus (Richard et al. 2016: fig. 33) and the epigastric area (unmodified (Fig. 6H) vs. with central goggle-shaped process (Richard et al. 2016: figs. 36B, C and D)).

China (Hunan, Guangxi) (Fig. 7).