Stylocellus Westwood, 1874

Clouse, Ronald M., 2012, The lineages of Stylocellidae (Arachnida: Opiliones: Cyphophthalmi), Zootaxa 3595 (1), pp. 1-34 : 7-8

Stylocellus Westwood, 1874

Stylocellus Westwood, 1874: 200 ; Pocock 1897: 290 –291; Roewer 1926: 263; Giribet 2000: 68. Removed from synonymy: Leptopsalis Thorell, 1882 : [synonymized by Thorell (1890: 106), but restored by Clouse and Giribet (in press)]

Type species: Stylocellus sumatranus Westwood, 1874 , by monotypy.

Other species included: Stylocellus lornei sp. nov.

Comments: The two species in this genus are nearly identical in size and proportion ( Fig. 7 ; males approximately 6 mm long and 3 mm wide across the opisthosoma), and the wider measurement across the ozophores of S. sumatranus could easily be caused by its pinning, which has clearly split and widened the ventral prosomal complex. Still, given the multiple evolution of various sizes and associated features in the family, the similar proportions could be causing these species to appear more closely related than they truly are. Thus, the diagnosis relies on other features I think give the two species a strong overall resemblance and which have clearly influenced their placement in morphometric phylogenies. Diagnostic features from the male fourth tarsus are based solely on S. lornei , sp. nov., as the type of S. sumatranus is missing this appendage.

Description: Stylocellinae, with the following: anal gland pores and medial anal plate sculpturing present; second cheliceral article more than 2/3 granulated, granulations stopping before joint with third article, bordered by long lateral smooth patch and low ridge that extends to third article joint; Rambla’s organ at same level with surrounding tarsus, lacking microgranulations, the larger, pointed tuberculate-granulations sometimes smaller or missing at the center of the organ but mostly continuing across as on the surrounding cuticle; ozophores long and parallel-sided, almost widening at the tip; ventral prosomal complex large, with fourth coxae meeting for a length longer than the gonostome, distinct sternum present, and second coxae broadly meeting; sternal opisthosomal sulci between sternites 3 and 4, 4 and 5, and 5 and 6 distinct and sinusoidal.

Distribution: Sumatra and Phayam Island, off the west coast of Peninsular Thailand

Figures

FIGURE 7. Stylocellus lornei, sp. nov., male paratype (SPM 006159): A, dorsal; B, ventral, C, lateral. Scale bar = 1.00 mm for all views.