Taxonomic study of the genus Ischnothyreus Simon, 1893 from Myanmar (Araneae, Oonopidae)

Abstract Seven new species of the genus Ischnothyreus Simon, 1893 from the spider family Oonopidae Simon, 1890 are reported from Myanmar: I. hponkanrazisp. nov. (♀), I. jianglangisp. nov. (♀), I. meukyawwasp. nov. (♂♀), I. putaosp. nov. (♀), I. qiuxingsp. nov. (♀), I. taunggyisp. nov. (♂♀) and I. zhigangisp. nov. (♂♀). Morphological descriptions and photographic illustrations of the new species are given. All types are preserved in the Institute of Zoology, Chinese Academy of Sciences (IZCAS).


Introduction
The genus Ischnothyreus was established by Simon in 1893, with Ischnaspis peltifer Simon, 1892 from Saint Vincent in the Caribbean as the type species (Simon 1893). This genus is an Old World taxon, being represented in the New World by only two species, I. peltifer and I. velox Jackson, 1908, both of which are assumed to be introduced (Platnick et al. 2012;Brescovit et al. 2019).
The genus Ischnothyreus Simon, 1893 can be recognized by the presence of leg spines, the usually small abdominal scutum, the strongly sclerotized male palps, the heavily sclerotized male endites, and the winding genital tube in females (Kranz-Baltensperger 2011). There are currently 107 valid specific names assigned to Ischno thyreus (Li 2020;WSC 2020) and even more are waiting to be described (Richard et al. 2016).
In this paper seven new Ischnothyreus species collected from Myanmar are described and illustrated. This work presents the first record and description of species Ischnothyreus from Myanmar.

Materials and methods
The specimens were examined in 95% ethanol using a Leica M205C stereomicroscope. Details were studied with an Olympus BX51 compound microscope. Photos were taken with a Canon EOS 750D zoom digital camera (18 megapixels) mounted on an Olympus BX51 compound microscope. Vulvae were cleared in lactic acid. Scanning electron microscope images (SEM) were taken under high vacuum with a Hitachi TM3030 after critical point drying and gold-palladium coating. All measurements were taken using an Olympus BX51 compound microscope and are given in millimeters in the text. The specimens are preserved in the Institute of Zoology, Chinese Academy of Sciences (IZCAS) in Beijing, China (curator: Jun Chen).
Description. Female (holotype). Body: habitus as in Fig. 1A-C; body length 2.40. Carapace: 1.08 long, 0.98 wide; pale brown, without any pattern, ovoid in dorsal view, slightly elevated in lateral view, surface finely reticulate, fovea absent, lateral margin straight, smooth (Fig. 1D, F). Clypeus: height about equal to ALE radius or more (Fig. 1G). Eyes: six, in one group, well developed, subequal, ALE circular, PME and PLE oval, posterior eye row procurved from both above and front (Fig. 1D, G). Sternum: as long as wide, pale orange, uniform, not fused to carapace, surface smooth, setae sparse (Fig. 1E). Mouthparts: chelicerae, endites and labium orange; chelicerae straight, base of fangs unmodified (Fig. 1G); labium rectangular, not fused to sternum, anterior margin not indented at middle; endites unmodified ( Fig. 1E). Abdomen: 1.33 long, 0.74 wide; dorsal scutum well sclerotized, pale brown, covering 1/3 of the abdomen width and approximately 1/3 of the abdomen length, not fused to epigastric scutum; epigastric and postgastric scutum well sclerotized, pale orange, unfused (Fig. 1A, B). Legs: pale orange, femur I with two prolateral spines, tibia I with four pairs, metatarsus I with two pairs of long ventral spines. Leg II spination is similar to leg I except femur with only one prolateral spine. Legs III and IV spineless. Epigastric area: surface without external features (Fig. 1H). Endogyne: from the middle of the slightly thickened margin of the postgastric scutum runs a dark winding tube posteriorly, ending in a bell-shaped atrium (Fig. 16A, B).
Male. Unknown. Etymology. The specific name is a noun in apposition taken from the type locality. Distribution. Known only from the type locality.  Kranz-Baltensperger, 2011 in the triangular shaped atrium, but can be distinguished by shape of the dorsal abdominal scutum (width/length = 1/2 ( Fig. 2A) Fig. 2A-C; body length 2.35. Carapace: 1.02 long, 0.87 wide; brown, without any pattern, ovoid in dorsal view, slightly elevated in lateral view, surface finely reticulate, fovea absent, lateral margin straight, smooth (Fig. 2D, F). Clypeus: height about equal to ALE radius or less (Fig.  2G). Eyes: six, in one group, well developed, subequal, ALE circular, PME and PLE oval, posterior eye row procurved from both above and front (Fig. 2D, G). Sternum: as long as wide, pale brown, uniform, not fused to carapace, surface smooth, setae sparse (Fig.  2E). Mouthparts: chelicerae, endites and labium pale brown; chelicerae straight, base of fangs unmodified (Fig. 2G); labium rectangular, not fused to sternum, anterior margin not indented at middle; endites unmodified ( Fig. 2E). Abdomen: 1.42 long, 1.01 wide; dorsal scutum covering less than 1/2 of the abdomen length and 1/3 of the abdomen width, not fused to epigastric scutum; epigastric and postgastric scutum well sclerotized, pale orange, unfused ( Fig. 2A, B). Legs: pale orange, femur I with two prolateral spines, tibia I with four pairs, metatarsus I with two pairs of long ventral spines. Leg II spination is similar to leg I except femur with only one prolateral spine. Legs III and IV spineless. Epigastric area: surface without external features (Fig. 2H). Endogyne: from the middle of the slightly thickened margin of the postgastric scutum runs a dark, simple winding tube posteriorly, ending in a black, triangular shaped atrium (Fig. 17A, B).

Description. Female (holotype). Body: habitus as in
Male. Unknown. Etymology. The species is named after Mr Jianglang Wu, one of the collectors of the holotype; noun in genitive case.
Distribution. Known only from the type locality.    ( Fig. 3D, F). Clypeus: height about 2/3 of ALE diameter (Fig. 3G). Eyes: six, in one group, well developed, subequal, ALE circular, PME and PLE oval, posterior eye row recurved from above, procurved from front (Fig. 3D, G). Sternum: as long as wide, pale orange, uniform, not fused to carapace, surface smooth, setae sparse (Fig. 3E). Mouthparts: chelicerae, endites and labium orange; chelicerae straight, base of fangs with crown-shaped sclerotized process with serrated exterior margin, fang groove with a few small denticles (Figs 3H, I, 15A, B); labium rectangular, not fused to sternum, anterior margin not indented at middle; anteromedian tip of endites with one strong, tooth-like projection (Fig. 3E). Abdomen: 0.84 long, 0.43 wide; dorsal scutum well sclerotized, pale orange, covering whole abdomen width and approximately 5/6 of the abdomen length, not fused to epigastric scutum; epigastric and postgastric scutum well sclerotized, pale orange, fused, postgastric scutum covering about 5/6 of the abdomen length ( Fig. 3A-C). Legs: pale orange, femur I with three prolateral and two small retrolateral spines, tibia I with four pairs, metatarsus I with two pairs of long ventral spines. Leg II spination is similar to leg I except femur with only two prolateral and one retrolateral spine. Legs III and IV spineless. Palp: strongly sclerotized, trochanter with ventral projection, cymbium brown, fused with bulb; bulb brown, with one large and one very small ventral protuberance, distal end of bulb elongated, with one broad leaf-shaped prolateral projection and distal hook-shaped membrane, retrolateral lobe narrow (Figs 4, 14A-C).
Etymology. The specific name is a noun in apposition taken from the type locality. Distribution. Known only from the type locality.  (Fig. 17C) (vs small, bell-shaped atrium; Fig. 17E), and the smoothly curved posterior margin of postgastric scutum (Fig. 6H) (vs straight posterior margin; Fig. 13H).
Male. Unknown. Etymology. The specific name is a noun in apposition taken from the type locality. Distribution. Known only from the type locality. Description. Female (holotype). Body: habitus as in Fig. 7A-C; body length 2.01. Carapace: 0.87 long, 0.72 wide; yellow, without any pattern, ovoid in dorsal view, strongly elevated in lateral view, surface finely reticulate, fovea absent, lateral margin straight, smooth (Fig. 7D, F). Clypeus: height about equal to ALE radius or less (Fig. 7G). Eyes: six, in one group, well developed, subequal, ALE circular, PME and PLE oval, posterior eye row recurved from above, procurved from front (Fig. 7D, G). Sternum: as long as wide, yellow, uniform, not fused to carapace, surface smooth, setae sparse (Fig. 7E). Mouthparts: chelicerae, endites and labium orange; chelicerae straight, base of fangs unmodified (Fig. 7G); labium rectangular, not fused to sternum, anterior margin not indented at middle; endites unmodified (Fig. 7E). Abdomen: 1.35 long, 0.92 wide; dorsal scutum weakly sclerotized, very small, not fused to epigastric scutum; epigastric and postgastric scutum well sclerotized, pale orange, unfused (Fig. 7A, B). Legs: pale orange, femur I with two prolateral spines, tibia I with four pairs, metatarsus I with two pairs of long ventral spines. Leg II spination is similar to leg I except femur with only one prolateral spine. Legs III and IV spineless. Epigastric area: surface without external features (Fig. 7H). Endogyne: from the middle of the slightly thickened margin of the postgastric scutum runs a dark, very simple winding tube posteriorly, ending in a circular atrium (Fig. 16E, F).

Ischnothyreus qiuxing
Male. Unknown. Etymology. The specific name is derived from Chinese pinyin, "qiuxing", which means "circular", referring to the circular atrium; noun in apposition.
Distribution. Known only from the type locality.  Fig. 11B) of male, and the long abdominal dorsal scutum (less than 1/2 of the abdomen length (Fig. 10A) vs very small; Fig. 13A) and the nipple-shaped atrium (Fig. 16G) (vs inverted bell-shaped atrium; Fig. 17E) of female.

Ischnothyreus taunggyi
Description. Male (holotype). Body: habitus as in Fig. 8A-C; body length 1.71. Carapace: 0.84 long, 0.63 wide; pale brown, with egg-shaped patches behind eyes, ovoid in dorsal view, strongly elevated in lateral view, surface of elevated portion of pars cephalica smooth, sides finely reticulate, fovea absent, lateral margin straight, smooth (Fig. 8D). Clypeus: height about equal to ALE radius or more. Eyes: six, in one group, well developed, ALE largest, ALE circular, PME and PLE oval, posterior eye row recurved from above, procurved from front (Fig. 8D). Sternum: as long as wide, pale orange, uniform, not fused to carapace, surface smooth, setae sparse (Fig. 8E). Mouthparts: chelicerae, endites and labium orange; chelicerae straight, with crown-shaped sclerotized process at base of fangs, fang groove with a few small and one larger denticles (Fig. 15C, D); labium rectangular, not fused to sternum, anterior margin not indented at middle; anteromedian tip of endites with one strong, tooth-like projection (Fig. 8E). Abdomen: 0.74 long, 0.49 wide; dorsal scutum well sclerotized, pale orange, covering 2/3 the abdomen width and approximately 3/4 of the abdomen length, unfused to epigastric scutum; epigastric and postgastric scutum well sclerotized, pale orange, fused, postgastric scutum covering about 4/5 of the abdomen length (Fig. 8A, B). Legs: pale orange, femur I with three prolateral and one small retrolateral spines, tibia I with four pairs, metatarsus I with two pairs of long ventral spines. Leg II spination is similar to leg I except femur with only two prolateral spines. Legs III and IV spineless. Palp: strongly sclerotized, trochanter with ventral projection, cymbium brown, fused with bulb; bulb brown, with two large ventral protuberances, distal end of bulb   elongated, with one leaf-shaped prolateral projection and distal needle like membrane, retrolateral lobe broad, ear-shaped (Figs 9, 14D-F).
Etymology. The specific name is a noun in apposition taken from the type locality. Distribution. Known only from the type locality. Description. Male (holotype). Body: habitus as in Fig. 11A-C; body length 2.08. Carapace: 1.03 long, 0.87 wide; pale brown, with egg-shaped patches behind eyes, ovoid in dorsal view, strongly elevated in lateral view, surface of elevated portion of pars cephalica smooth, sides finely reticulate, fovea absent, lateral margin straight, smooth (Fig. 11D). Clypeus: height about equal to ALE radius or more. Eyes: six, in one group, well developed, subequal, ALE circular, PME and PLE oval, posterior eye row straight from above, procurved from front (Fig. 11D). Sternum: as long as wide, pale brown, uniform, not fused to carapace, surface smooth, setae sparse (Fig. 11E). Mouthparts: chelicerae, endites and labium orange; chelicerae straight, base of fangs with crownshaped sclerotized process with serrated exterior margin (Figs 11G, H, 15E, F), fang groove with a few small denticles; labium rectangular, not fused to sternum, anterior margin not indented at middle; anteromedian tip of endites with one strong, toothlike projection (Fig. 11E). Abdomen: 1.07 long, 0.72 wide; dorsal scutum weakly sclerotized, pale orange, very small, not fused to epigastric scutum; epigastric and     postgastric scutum weakly sclerotized, pale orange, fused, postgastric scutum very small (Fig. 11A, B). Legs: pale orange, femur I with three prolateral spines, tibia I with four pairs, metatarsus I with two pairs of long ventral spines. Leg II spination is similar to leg I except femur with only two prolateral spines. Legs III and IV spineless. Palp: strongly sclerotized, trochanter with ventral projection, cymbium brown, fused with bulb; bulb brown, with one large ventral protuberance, distal end of bulb elongated, with one narrow leaf-shaped prolateral projection, retrolateral lobe small, simple (Figs 12, 14G-H). Abbreviations: a = apodemes; ass = anchor-shaped structure; bsa = bell-shaped atrium; csa = circular atrium; nsa = nipple-shaped atrium; oa = opening of the atrium; wt = winding tube. Scale bars: 0.2 mm.
Etymology. The species is named after Mr Zhigang Chen, one of the collectors of the holotype; noun in genitive case.
Distribution. Known only from the type locality.