Gamasomorpha jacobsoni, Bai & Bian & Tong & Hörweg, 2025

Bai, Yang, Bian, Dongju, Tong, Yanfeng & Hörweg, Christoph, 2025, Three new species of the genus Gamasomorpha Karsch, 1881 (Araneae, Oonopidae) from the Philippines and Sumatra, Indonesia, ZooKeys 1258, pp. 313-331 : 313-331

Gamasomorpha jacobsoni sp. nov.

Figs 6 , 7 , 8 , 12 G – I

Material examined.

Holotype Indonesia • ♂ ( NHMW -ZOO-AR-30393 ); Sumatra, Fort de Kock ; leg. E. R. Jacobson . Paratypes. Indonesia • 2 ♂ 18 ♀ ( NHMW -ZOO-AR-30394 ); same data as holotype .

Etymology.

The specific name is named after the collector, the Dutch entomologist Edward Richard Jacobson (1870–1944).

Diagnosis.

The new species is similar to G. coniacris Eichenberger, 2012 from Malaysia and Indonesia in the smooth carapace and the broadly-oval receptacle, but can be distinguished by the radial furrow of sternum lacking the droplike pits (vs with droplike pits; cf. Fig. 6 G and Eichenberger et al. 2012: fig. 20 D), the scuto-pedicel region without scutal ridges (vs with paired curved scutal ridges; cf. Fig. 8 H and Eichenberger et al. 2012: fig. 20 H), and the bulb with a round conical extension (vs triangular; cf. Figs 7 A , 12 G and Eichenberger et al. 2012: fig. 21 D – F).

Description.

Male ( holotype). Total length 1.50; carapace 0.59 long, 0.47 wide; abdomen 0.90 long, 0.51 wide. Habitus as in Fig. 6 A – C . Body yellow, chelicerae and legs lighter. Carapace (Fig. 6 D, E, F ): surface smooth; pars cephalica slightly elevated in lateral view. Eyes (Fig. 6 D, E ): ALE largest, PLE and PME nearly equal size; posterior eye row straight viewed from above, procurved from front; ALE nearly touching; ALE separated from edge of carapace by about 0.6 times their diameter. Sternum (Fig. 6 G ): smooth, with narrow, transverse palpal groove, radial furrows present. Abdomen (Fig. 6 A – C ): dorsal scutum ovoid, punctate, densely covered with short setae; booklung covers middle size; pedicel tube short, without dorsolateral extension; scuto-pedicel region without scutal ridge. Palp (Figs 7 A – F , 12 G – I ): pale-orange; bulb distally tapering, ending as round conical extension ( ce); cymbium not extending beyond distal tip of bulb; embolus ( em) dark, long, slender, lamellar; embolic accessory appendage ( ma) with a subdistal excavation; conductor ( co) shorter, lamellar.

Female ( paratype). Total length 1.66; carapace 0.58 long, 0.48 wide; abdomen 0.96 long, 0.58 wide. Habitus (Fig. 8 A – C ) as in male, except as noted. Epigastric area (Fig. 8 G, I ): externally without special features. Endogyne (Fig. 8 J ): receptacle ( re) broadly oval, with ovoid secretory sac ( ssa), globular appendix ( gap) about half the length of receptacle, with an anterior paddle-like sclerite ( psc) and a nail-like process ( na), with lateral sclerites functioning as muscle attachments.

Distribution.

Known only from the type locality (Fig. 13 ).

Figures

Figure 6. Gamasomorpha jacobsoni sp. nov., male holotype. A – C. Habitus, dorsal, lateral and ventral views; D – G. Prosoma, anterior, dorsal, lateral and ventral views. Scale bars: 0.4 mm.

Figure 7. Gamasomorpha jacobsoni sp. nov., male left palp, SEM. A, C, E. Prolateral, dorsal and anterior-retrolateral views; B, D, F. Distal part of bulb, prolateral, dorsal and anterior-retrolateral views, arrow shows the subdistal excavation. Abbreviation: ce = conical extension; co = conductor; em = embolus; ma = mesal embolic accessory appendage. Scale bars: 0.1 mm.

Figure 8. Gamasomorpha jacobsoni sp. nov., female paratype. A – C. Habitus, dorsal, lateral and ventral views; D – F. Prosoma, dorsal, lateral and ventral views; G, H. Abdomen, ventral and anterior views; I. Epigastric region, ventral view; J. Endogyne, dorsal view. Abbreviations: gap = globular appendix; na = nail-like process; psc = paddle-like sclerite; re = receptacle; ssa = secretory sac. Scale bars: 0.4 mm (A – H); 0.1 mm (I, J).

Figure 12. Gamasomorpha spp., male left palp. A – C. G. bakeri sp. nov.; D – F. G. fortdekock sp. nov.; G – I. G. jacobsoni sp. nov.; J – L. G. shoushanensis (Tong & Li, 2014). A, D, G, J. Prolateral view; B, E, H, K. Dorsal view; C, F, I, L. Retrolateral view. Scale bars: 0.1 mm.

Figure 13. Distribution records of the four Gamasomorpha species: 1. G. bakeri sp. nov.; 2. G. fortdekock sp. nov.; 3. G. jacobsoni sp. nov.; 4. G. shoushanensis (Tong & Li, 2014).