Twenty-eight new species of the spider genus Merizocera Fage, 1912 (Araneae, Psilodercidae) from South and Southeast Asia

Abstract Previously, the genus Merizocera Fage, 1912 comprised only seven species from Indonesia, Malaysia, Sri Lanka, and Thailand. In this study, 28 new species are described from South and Southeast Asia: M. baoshan Li, sp. nov. (♂♀), M. betong Li, sp. nov. (♂♀), M. colombo Li, sp. nov. (♂♀), M. galle Li, sp. nov. (♂♀), M. hponkanrazi Li, sp. nov. (♂), M. kachin Li, sp. nov. (♂♀), M. kandy Li, sp. nov. (♂♀), M. mandai Li, sp. nov. (♂♀), M. krabi Li, sp. nov. (♂♀), M. kurunegala Li, sp. nov. (♂♀), M. lincang Li, sp. nov. (♀), M. mainling Li, sp. nov. (♂♀), M. nyingchi Li, sp. nov. (♀), M. peraderiya Li, sp. nov. (♂♀), M. phuket Li, sp. nov. (♂♀), M. putao Li, sp. nov. (♂♀), M. ranong Li, sp. nov. (♂♀), M. ratnapura Li, sp. nov. (♂♀), M. salawa Li, sp. nov. (♂), M. tak Li, sp. nov. (♀), M. tanintharyi Li, sp. nov. (♂♀), M. tengchong Li, sp. nov. (♂), M. thenna Li, sp. nov. (♂♀), M. uva Li, sp. nov. (♀), M. wenshan Li, sp. nov. (♂♀), M. wui Li, sp. nov. (♂♀), M. yala Li, sp. nov. (♀), and M. yuxi Li, sp. nov. (♂♀). Among them the genus Merizocera is reported for the first time from China, Myanmar, and Singapore.

In this paper, 28 new species of Merizocera collected in southern China, Myanmar, Singapore, Sri Lanka, and Thailand are described and illustrated. This is the first record of the genus in China, Myanmar, and Singapore.

Materials and methods
Types are deposited in the Institute of Zoology, Chinese Academy of Sciences (IZ-CAS) in Beijing. All specimens collected were studied and preserved in 75% ethanol. The specimens were measured and examined with a Leica M205 C stereomicroscope and further morphological details were observed with an Olympus BX41 compound microscope. Male palps were detached from the left side of the animal for further examination. Carapace length was measured excluding the clypeus. Internal genitalia of the female and palpal bulbs were dissected and immersed in lactic acid. An Olympus C7070 wide zoom digital camera (7.1 megapixels) mounted on an Olympus SZX12 stereomicroscope was used to take photos at different focal planes. The photos were then transferred to the image stacking software Helicon Focus 6.7.1 to generate photos with a greater depth of field before further processing with Adobe Photoshop CC 2014. Leg measurements are shown as total length: femur, patella, tibia, metatarsus and tarsus. Leg segments were measured from their retrolateral side. All measurements are given in millimetres (mm). All terminology follows that of Li et al (2014). The distribution map was generated with Google Earth Pro 7.3.2 (Google Limited Liability Company).  County, Baoshan, Yunnan, China, 15 July 2016, Y. Li leg. Paratypes: 3 males and 3 females (IZCAS), same data as holotype.
Etymology. The specific name refers to the type locality; noun in apposition. Diagnosis. Males of M. baoshan sp. nov. resemble those of M. tengchong sp. nov., but can be distinguished by the pointed and bent tip of the embolus (Fig. 1B) (vs. blunt and upright tip of embolus (Fig. 40B)); a distinct stalked apophysis bearing a pointed distal tip adjacent to the embolus (Fig. 1B) (vs. stalked apophysis bearing globose distal tip (Fig. 40B)); a cymbial protrusion half the length of the tegular (Fig. 1D) (vs. cymbial protrusion 1/4 the length of tegular (Fig. 40D)). The female can be distinguished from congeners by a pair of flattened ovoid spermathecae.
Female (paratype). General features and colouration similar to those of the male (Fig. 4D 5D) (vs. inconspicuous cymbial protrusion approx. 1/3 the length of bulb), conductor bifurcate and distinctly shorter than embolus (Fid. 5B) (vs. conductor not bifurcate and almost similar length with embolus). Females can be distinguished by having a pair of elongated spermathecae concaving posteriorly (Fig. 6A).

Merizocera kachin
Description. Male (holotype). Total length 1.44; carapace 0.67 long, 0.56 wide; abdomen 0.79 long, 0.74 wide. Carapace circular, brownish, with dark brown radiating marks (Fig. 12C). Fovea shallow. Thoracic region distinctly elevated medially. Clypeus brownish, with small protrusion provided with long setae. Labium dark brown. Sternum dark brown, with distinct dark radiating lines. Abdomen ovoid, dark grey (Fig. 12C Fig. 11A-D): femur slender, four times longer than patella; patella not swollen; tibia half length of femur; cymbium with distal protrusion, half length of femur, length ratio of dorsal elongation and cymbium 0.28; bulb pale yellow, elongated pyriform with embolus and conductor arising distally; embolus hooked, almost similar in length with tegular, with pointed tip, width of anterior horizontal hooked part half width of tegular; conductor short with pointed tip, basally connected with embolus.
Female (paratype). General features and colouration similar to those of male except for the absence of clypeus protrusion (Fig. 12D Etymology. The specific name refers to the type locality; noun in apposition. Diagnosis. Males can be distinguished from other congeners by the blunt bifurcate embolus tip, two similar components of conductor, and swollen bulb with a notch anteriorly (Fig. 13B). The females can be distinguished by a pair of angular shaped tubular spermathecae (Fig. 14A).  Description. Male (holotype). Total length 1.33; carapace 0.63 long, 0.54 wide; abdomen 0.63 long, 0.56 wide. Carapace rounded, brownish, with dark brown marks laterally and dark median stripe on anterior half (Fig. 14C). Fovea shallow. Thoracic region distinctly elevated medially. Clypeus brownish with dark brown marks medially. Labium dark brown. Sternum dark brown with distinct dark radiating lines. Abdomen ovoid, brownish, with dark brown marks dorsally and ventrally. Legs brown; measurements: I 6.48 (1.70, 0.19, 1.96, 1.76, 0.87), II 4.51 (1.19, 0.20, 1.30, 1.18, 0.64), III 3.66 (0.98, 0.20, 1.05, 0.96, 0.47), IV missing. Palp ( Fig. 13A-D): femur slender, thrice longer than patella, patella not swollen; tibia swollen, twice wider than and almost similar in length to femur; cymbium with distal protrusion, half as long as femur, length ratio of dorsal elongation and cymbium 0.59; bulb brown, with embolus and conductor arising distally, tegular with a notch anteriorly; embolus bifurcated with blunt tips, two similar components of conductor resemble a C-shape attached adjacent to embolus.
Distribution. Known only from the type locality (Singapore; Fig. 54). Etymology. The specific name refers to the type locality; noun in apposition. Diagnosis. Diagnosis features of males are discussed under M. hponkanrazi sp. nov. Males can be distinguished by an elongated pyriform bulb with a triangular conductor adjacent to the base of the embolus (Fig. 17D), embolus approx. half as long as the tegulum. The females can be distinguished from congeners by two pairs of twisted stalked spermathecae bearing globose distal ends (Fig. 18A).

Merizocera kurunegala
Description. Male (holotype). Total length 1.33; carapace 0.67 long, 0.53 wide; abdomen 0.65 long, 0.49 wide. Carapace circular, brownish, with dark brown marks laterally and dark brown median stripe on anterior half (Fig. 20C)   patella not swollen; tibia slightly swollen proximally, twice wider and half length of femur; cymbium with distal protrusion, half length of femur, length ratio of dorsal elongation and cymbium 0.64; bulb pale yellow; embolus dark, evenly bent, twice as long as bulb; conductor trifurcate with two pointed upwards, and third pointed downwards, stem of conductor thrice wider than that of embolus.
Female (paratype). General features and colouration similar to those of male (Fig. 23D, E)   Diagnosis. Females can be distinguished from congeners by two pairs of twisted stalked spermathecae bearing globose distal ends, where lateral pairs are at least half as short as median pairs and have globose ends twice the size of the former (Fig. 24A).

Merizocera peraderiya
Description. Male (holotype). Total length 1.33; carapace 0.66 long, 0.59 wide; abdomen 0.67 long, 0.46 wide. Carapace circular, brownish, with dark brown marks laterally and dark brown median stripe on anterior half (Fig. 26C). Fovea shallow. Thoracic region distinctly elevated medially. Clypeus brownish, with dark brown marks medially. Labium dark brown. Sternum dark brown but lighter medially. Abdomen slightly elongated, dark grey, with dark brown marks dorsally and ventrally.  (Fig. 25A-D): femur slender, 2.5 times longer than patella; patella not swollen; tibia slightly swollen, half as long as femur; cymbium with distal protrusion, length ratio of dorsal elongation and cymbium 0.72; bulb pale yellow, pyriform with embolus and conductor arising distally; embolus thin and dark with pointed tip, emerging laterally, bent at right-angle; conductor basally attached with embolus, bifurcate, one slender and slightly bent, the other hooked and twice as wide, conductor stem half as long as the width of bulb.   Female (paratype). General features and colouration similar to those of male (Fig. 26D, E) (Fig. 26B): dark brown, patch nearly elliptical. Endogyne (Fig. 26A) with a pair of twisted S-shaped spermathecae, ratio of the width of spermatheca to the interdistance of spermathecae 1:4.
Female (paratype). Similar to male in colouration and general features but slightly larger (Fig. 28D, E)  medially with horizontal pale brown slit. Endogyne (Fig. 28A) with a pair of slight horizontally angled elongated spermathecae, tip pointed upright, ratio of the width of spermatheca to the interdistance of spermathecae 1:4.
Distribution. Known only from the type locality (Myanmar; Fig. 53).   Etymology. The specific name refers to the type locality; noun in apposition. Diagnosis. Diagnosis features of males and females are discussed in M. betong sp. nov. Males with a crinkly embolus, lamina-like embolus tip, and swollen pyriform bulb (Fig. 31B). Females with a pair of posteriorly directed tubular spermathecae (Fig. 32A).
Distribution. Known only from the type locality (Thailand; Fig. 54). Etymology. The specific name refers to the type locality; noun in apposition. Diagnosis. Diagnosis features of males and females are discussed in M. phuket sp. nov. Males with a thick and short conductor and a gradually tapering embolus (Fig. 33B). Females with a pair of tubular spermathecae laterally and stalked spermathecae medially (Fig. 34A).
Distribution. Known only from the type locality (Sri Lanka; Fig. 52). Etymology. The specific name refers to the type locality; noun in apposition. Diagnosis. Diagnosis features of males are discussed in M. mandai sp. nov. Bulb with a widely separated bifurcate conductor, and a curved embolus (Fig. 35B).
Female. Unknown. Distribution. Known only from the type locality (Sri Lanka; Fig. 52). Etymology. The specific name refers to the type locality; noun in apposition. Diagnosis. Females can be distinguished from all congeners by the presence of two pairs of globose spermathecae, the median pair resembling the figure '8' (Fig. 37A).
Male. Unknown. Distribution. Known only from the type locality (Thailand; Fig. 54). Etymology. The specific name refers to the type locality; noun in apposition. Diagnosis. Diagnosis features of males and females are discussed in M. mainling sp. nov. Recognised by a wide and appendage-like conductor as long as the embolus (Fig. 38B). It can be distinguished from the Psiloderces leucopygius group by an inconspicuous cymbial protrusion and a distinct conductor (vs. distinct or short cymbial protrusion and an inconspicuous conductor in the leucopygius group).
Distribution. Known only from the type locality (Myanmar; Fig. 54). Etymology. The specific name refers to the type locality; noun in apposition. Diagnosis. Males can be recognised from congeners by the webbed feet-like embolus with a basally attached, stalked apophysis bearing a globose tip (Fig. 40B).
Female. Unknown. Distribution. Known only from the type locality (China; Fig. 53).  Etymology. The specific name refers to the type locality; noun in apposition. Diagnosis. Males can be recognised from all other congeners by the twisted widened embolus and a trifurcate conductor (Fig. 42B). Females can be distinguished by a pair of horizontal, slender, stalked spermathecae, both ends bearing globose distal parts (Fig. 43A).
Female (paratype). Similar to male in colouration and general features but slightly larger (Fig. 46D (Fig. 46B): dark brown semi-circular patch. Endogyne (Fig. 46A) with a pair of anteriorly directed tubular spermathecae, ratio of the width of a spermatheca to the interdistance of spermathecae 1:5.

Merizocera wui
Female (paratype). Similar to male in colouration and general features but slightly larger (Fig. 48D, E) (Fig. 48B): dark brown oval patch, medially with a pale brown slit. Endogyne (Fig. 48A) with a pair of clavate spermathecae, slightly angled toward each other, ratio of the width of a spermatheca to the interdistance of spermathecae 1:5.
Male. Unknown. Distribution. Known only from the type locality (Thailand; Fig. 54). Etymology. The specific name refers to the type locality; noun in apposition. Diagnosis. Diagnosis features of males and females are discussed in M. betong sp. nov. Males with swollen pyriform bulb, and embolus with a crinkly and flattened tip (Fig. 50B). Females with two pairs of tubular spermathecae (Fig. 51A).
Female (paratype). Similar to male in colouration and general features but slightly larger (Fig. 51D Distribution. Known only from the type locality (China; Fig. 53).

Discussion
Males of Merizocera can be distinguished from Psiloderces by the following characters: In Merizocera the cymbium and bulb are of similar lengths, or rarely the bulb is longer than the cymbium. In contrast, the cymbium is generally longer than the bulb in Psiloderces. Merizocera can be divided into six morphological groups of species based on male palps.