Leptopsalinae subfam. nov.

Clouse, Ronald M., 2012, The lineages of Stylocellidae (Arachnida: Opiliones: Cyphophthalmi), Zootaxa 3595 (1), pp. 1-34 : 24-25

Leptopsalinae subfam. nov.

Comments: More than Stylocellinae, Leptopsalinae subfam. nov. provides a contrast between clear molecular support and subtle morphological synapomorphies, although here the morphological difficulty extends to the genera as well. The subfamily is best defined by its loss or moderation of character states easily noticed in other groups—they lack the enlarged coxae IV and swollen posterior prosomas of Fangensinae subfam. nov., the combination of sinusoidal sternal opisthosomal sulci, anal gland pores, large size, and knob-like ozophores of Stylocellus , and the deep ventral depression and flattened male tarsi IV of Meghalaya. Between the genera Leptopsalis and Miopsalis , most species can be easily placed by simply knowing the collection locality and whether males have anal gland pores: most species from Borneo, and miniature leptopsalines from Peninsular Malaysia and Sumatra with anal gland pores are in Miopsalis , and all species from Java, Sulawesi, and New Guinea, all of which lack anal gland pores, have been consistently recovered in Leptopsalis ( Clouse et al. 2009; Clouse & Giribet 2007; Clouse & Giribet 2010). There are species from Sarawak (northwestern Borneo), the Lingga-Riau islands and lower Peninsular Malaysia that resemble Miopsalis (in some cases even having anal gland pores) but are consistently recovered as members of Leptopsalis (usually as early lineages) in molecular phylogenies, but these are few. Nonetheless, given how many species are known from only one or two specimens, and the large areas yet unexplored, it seems probable that the above pattern will not hold, so we need to have more than a biogeographic diagnosis.

The species from northern Borneo ( Fig. 19 ) challenge any easy definitions of Miopsalis and Leptopsalis , as some of them have apparently converged strongly on the general appearance of Leptopsalis . Nine species have been described from Sabah and the nearby region around Gunung Mulu ( Hansen & Sørensen 1904; Rambla 1991; Shear 1993). The large species with known males— Miopsalis gryllospeca and M. silhavyi —have been recovered as Miopsalis easily in morphometric analyses, despite not having anal gland pores. Likewise, two of the smaller, more rounded species— M. collinsi ( Shear, 1993) and M. sabah ( Shear, 1993) —have anal gland pores and are also easily recovered as Miopsalis in morphometric phylogenies. However, smaller species that lack anal gland pores, M. kinabalu ( Shear, 1993) new comb. and M. leakeyi ( Shear, 1993) new comb., as well as the smallest species collected in the region with an anal gland pore, M. mulu ( Shear, 1993) new comb., are consistently recovered as members of Leptopsalis in morphometric phylogeneis. It can easily be seen why M. mulu new comb. groups with Leptopsalis despite its anal gland pore, for it has curved sternal opisthosomal sulci, an extremely concave posterior gonostome, compressed ventral prosomal complex, huge eyes, and rather uninformative, attenuate chelicerae. The reason why I consider M. mulu new comb., M. kinbalu new comb. and M. leakeyi new comb. convergent members of Miopsalis and not in Leptopsalis is that similar species collected by S. Kurbatov in 2002 from Mt. (Gunung) Kinabalu (“Borneo sp. 11” in recent phylogenetic analyses, MCZ DNA103249) and by A. Schulz from Gunung Mulu (“Borneo sp. 4,” MCZ DNA 101525, by) consistently place as Miopsalis in molecular phylogenies.

Certain derived Leptopsalis species have also converged on typical Miopsalis features, but these are more instructive and not so confounding in morphometric studies. A recently discovered species from New Guinea, L. lydekkeri ( Clouse & Giribet, 2007) , is never recovered outside of Leptopsalis in molecular studies, but it has a distinctly flattened dorsal scutum and a wide, flattened gonostome with a relatively straight posterior edge, as in Miopsalis . In Northern Sulawesi, L. hilyardi ( Shear, 1993) is a large species with small, tapered ozophores, long prosoma, and an elongate, elliptical overall soma shape, quite reminiscent of large Miopsalis species like M. silhavyi ( Fig. 20 ). From the dorsal view, these two species have nearly identical proportions, but the ventral prosomal complex is distinctly different and highlights one of the most general differences between the two leptopsaline genera. For L. hillyardi , the meeting of the first coxae, the posterior corners of the gonostome, and the posterior corners of the fourth coxae are all more anterior than in M. silhavyi . Combined with the concave posterior gonostome, lack of a distinct sternum, simple chelicerae, and lack of male anal gland pores, L. hillyardi is confidently placed in Leptopsalis . Indeed, morphometric phylogenetic analyses have grouped it with the other (much smaller and more rounded) species on Sulawesi, which is highly concordant with the history of the island ( Clouse et al. 2009).

Description: Eyes usually distinct and sometimes large, absent or reduced only in highly troglomorphic or miniaturized species; anal gland pores usually absent but variable; chelicerae often with reduced second ventral cheliceral process, first process often distinct or large; chelicerae ranging from claw-like to attenuate; granulations on second cheliceral article often highly reduced, low ridge absent; Rambla’s organ usually missing, if present then small, distinct, at the same level as surrounding cuticle, and with modified, scaly sculpturing ( Fig. 2 , A–D); ozophores usually tapered and pointing forward; posterior prosoma not bulging; lateral edges of fouth coxae tapered anteriorally; ventral prosomal complex variable; sternum variable; body profile variable, arching of dorsal scutum variable; sternal opisthosomal sulci between sternites 3 and 4, 4 and 5, and 5 and 6 ranging from straight to curved, sometimes indistinct; posterior gonostome highly variable, ranging from straight to deeply concave.

Included genera: Leptopsalis Thorell, 1882 (Type genus) and Miopsalis Thorell, 1890

Distribution: Central Thailand to western New Guinea, including the islands of Sumatra, Java, Sulawesi, Borneo, Palawan, and Mindanao.

Figures

FIGURE 2. The two most commonly recovered phylogenetic hypotheses for the genera of Stylocellidae. The only difference is the position of Giribetia, which is sometimes recovered as sister to Fangensis (A), forming a monophyletic Fangensinae, and sometimes recovered as sister to (Stylocellinae + Leptopsalinae) (B).

FIGURE 19. The nine described species from northern Borneo and two undescribed species included in recent molecular phylogenies. Described species are depicted as dorsal views of the type specimens and adjusted to the same scale (scale bar = 1.00 mm for all specimens). Locality number (1 – 4, as indicated on the central map) for each specimen is in the upper left corner of each photo, followed by an indication of whether males have anal gland pores (“ a ”) or are known from female specimens only (“ f ”). Miopsalis sabah (Shear, 1993) appears to have been collected at the same time as M. leakeyi (Shear, 1993), which the collection label indicates as “ G. Silum ” (mistakenly transcribed as “ Gunung Sabah ” in the description); this locality is most likely Gunung Silam.

FIGURE 20. Comparison of large Miopsalis and Leptopsalis species: A & C, M. silhavyi (Rambla, 1991); B & D, L. hillyardi (Shear, 1993). Specimens were scaled to the same length between the posterior edge and anterior coxae II; vertical lines indicate the posterior extent of coxae IV. Scale bars = 1.00 mm for both species.