Otacilia truncata, Dankittipakul, Pakawin & Singtripop, Tippawan, 2014

Dankittipakul, Pakawin & Singtripop, Tippawan, 2014, New species and new records of the spider genus Otacilia Thorell, 1897 (Araneae, Corinnidae) from Southeast Asia, Revue Suisse De Zoologie 121, pp. 383-394 : 383

Otacilia truncata sp. n. Figs 1-16

HOLOTYPE: ♂; Thailand, Chiang Mai Province and District, Doi Suthep-Pui National Park, 1180 m; pitfall traps 28.IV.-30.V.1986; leg. P.J. Schwendinger (MHNG).

PARATYPES: 3♀, 3♂; same data as for holotype (MHNG).

DIAGNOSIS: The male of O. truncata sp. n. can be distinguished from its congeners by the thick and sinuous retrolateral palpal tibial apophysis (Figs 1, 4, 7, 9-10, 12), by the dorsal tibial apophysis gradually tapering then abruptly becoming a threadlike filament at its half length (Figs 2-4, 11), and by the sigmoid membranous conductor (Fig. 1). The female can be recognized by the elongated V-shaped copulatory ducts (Figs 5-6, 13) connected to posteriorly located spermathecae (Figs 6, 13).

RELATIONSHIP: Males of this new species resemble those of O. onoi Deeleman- Reinhold, 2001 (RMNH, examined) in having a large, apical conductor and a curved embolus, but differ in having a palpal tibial apophysis of different shape. Females closely resemble those of O. armatissima Thorell, 1897 (MSNG, examined) in having elongated, V-shaped copulatory ducts, but in O. armatissima the epigynal region is much wider, occupying the entire epigastric region. The spermathecae of O. armatissima are digitiform (multilocular in O. truncata sp. n., Figs 6, 13).

ETYMOLOGY: The specific epithet refers to the large, truncated RTA of the male palp (Fig. 12).

DESCRIPTION OF MALE (HOLOTYPE): Total length 3.5; prosoma 1.6 long, 1.4 wide; opisthosoma 1.9 long, 1.0 wide.

Prosoma: Broadest between coxae II and III, narrowed in cephalic region at coxae I, in profile highest just in front of fovea. Carapace yellowish brown, with dark green striae radiating from black, longitudinal fovea. Sternum yellow, subovoid, slightly longer than wide, posteriorly bluntly pointed, devoid of distinctive projection between leg coxae. Labium wider than long, anterior margin slightly curved. Palpal coxae subrectangular, with thin apical scopulae. Cheliceral fang slender, moderately long; fang grooves with three promarginal and two retromarginal teeth; frontal surface of chelicerae each with two slender bristles.

Eyes: Eight eyes arranged in two rows, occupying almost entire attenuated cephalic region; AER straight, PER slightly recurved; PME smallest, other eyes subequal in size; PME pale and circular, others circled with black, diffuse ring. Eye sizes and interdistances: AME 0.08, ALE 0.10, PME 0.08, PLE 0.09; AME-AME 0.14, AME-ALE 0.12, PME-PME 0.18, PME-PLE 0.10, ALE-PLE 0.08; MOQ 0.30 long, anterior width 0.22, posterior width 0.25.

Legs: Leg formula 4123. Measurements: leg I 7.3 (1.6, 2.6, 1.7, 1.4); leg II 4.7 (1.3, 1.6, 1.0, 0.8); leg III 4.1 (1.1, 1.3, 0.8, 0.9); leg IV 8.4 (2.1, 2.4, 2.0, 1.9). Legs pale yellow, armed with orange-brown spines. Spination: all femora armed with two dorsal bristles situated in proximal half, widely separated on posterior legs; femora I and II with three elongated prolateral spines; tibia I with six pairs of ventral spines; metatarsi I and II with three pairs of ventral spines; tibia II with seven pairs of ventral spines; femora III and IV lacking prolateral spines; other leg segments devoid of large spines.

Opisthosoma: Elongate-ovoid, slightly widened posteriorly, sparsely clothed with fine pubescence. Dorsal scutum absent. Dorsum entirely dark green, except for pale yellow cardiac area. Venter pale yellow, posteriorly with dark greenish bands.

Palp (Figs 1-4, 7-12): Femur with subtriangular translucent ridge (Figs 2-3, 7). Retrolateral tibial apophysis represented by enlarged, sinuous prong (Figs 1, 4, 7, 9-10, 12); its anterior and posterior margins parallel in retrolateral view (Fig. 2); microscopically with narrow lumen running throughout its length (Figs 7, 9, 12). Dorsal tibial apophysis consisting of broad proximal region gradually tapering in proximal part and abruptly becoming a thin filament at half length (Figs 2-4, 11); tip of distal filament bent (Fig. 4). Tegulum ovoid, with sigmoid sperm duct located distally (Fig. 1). Embolus hook-shaped, sclerotized, originating distoprolaterally, its sharp apex pointing retrolaterad (Figs 1, 8). Conductor membranous, sigmoid, situated posterior to embolus (Fig. 1).

DESCRIPTION OF FEMALE (PARATYPE): Total length 5.4; prosoma 2.2 long, 2.0 wide; opisthosoma 3.2 long, 2.6 wide. Eye sizes and interdistances: AME 0.10, ALE 0.10, PME 0.08, PLE 0.09; AME-AME 0.10, AME-ALE 0.14, PME-PME 0.24, PME- PLE 0.12, ALE-PLE 0.30; MOQ 0.32 long, anterior width 0.22, posterior width 0.26. Leg formula 1423. Measurements: leg I 8.6 (2.2, 3.1, 1.5, 1.8); leg II 6.8 (1.9, 2.3, 1.1, 1.5); leg III 5.5 (1.7, 1.6, 1.4, 0.8); leg IV 7.7 (2.4, 2.2, 2.0, 1.1). General appearance as in male but larger. Dorsum of opisthosoma entirely dark green.

Genitalia (Figs 5-6, 13-16): Epigynal region lightly sclerotized, delimited from epigastric area by a distinct margin. Epigynal depressions (Figs 5-6) shallow, semicircular, with deeper crescent-shaped atrium (Fig. 5). Copulatory orifices circular (Figs 5-6, 13-14). Copulatory ducts with thick-walled anterior part, aligned horizontally (Figs 6, 14-15); posterior part thin and narrow, descending obliquely to connect with posteriorly-located spermathecae (Figs 5-6, 13). Spermathecae consisting of three chambers, posterior one subspherical (Figs 6, 13). Fertilization ducts lanceolate, originating from anterior chamber of spermathecae (Figs 6, 13). Anterior membranous bursae spherical, opening into anterior part of copulatory ducts (Figs 6, 13, 15).

VARIATION: There appear to be seven (instead of six) retroventral spines on tibia II in one of the male paratypes. A mating plug on one side of the epigynal atrium apparently has changed the configuration of the internal duct system (Figs 5-6, 13, 16). This raises the question whether previously described specimens with a similar plug in situ require cleaning to ensure appropriate identification and comparison. Although the differences may be modest, they should be observed with caution.

NATURAL HISTORY: All type specimens of O. truncata sp. n. were collected by means of pitfall trapping in an evergreen hill forest.

DISTRIBUTION: Known only from the type locality in northern Thailand.