Stenostygnus Simon, 1879

Mamani, Claudia Vanesa, Porto, Willians, Iglesias, Patricia P. & González, Abel Pérez-, 2021, Two new species of Stenostygnus from South America (Opiliones: Biantidae Stenostygninae), Zootaxa 4984 (1), pp. 182-202 : 183

Stenostygnus Simon, 1879

Stenostygnus Simon 1879: 224 . Roewer 1913: 163. 1923: 460. Mello-Leitão 1923: 133. 1932: 418. Sørensen in Henriksen 1932: 284. Kästner 1937: 389. Pinto-da-Rocha 1995: 194. Kury 2003: 36

Type species. Stenostygnus pusio Simon, 1879 (by monotypy).

Emended diagnosis. Area I without a median longitudinal groove ( Fig. 2 A ). Mesotergal areas and free tergites unarmed, only with scarce small granules or smooth ( Figs 2 A ; 8 A ). Male (α) chelicera not strongly swollen (only slightly bigger than in females) ( Fig. 6 C vs A). Patella of the pedipalp with or without meso-distal spine ( Fig. 3 D ). Males without metatarsus III enlarged. Males with armature on patella IV or tibia IV ( Figs 6 D ; 12 D, F ). Tarsal counts: 6–8(3): 9–15(3–4): 6: 6. Pars distalis of penis ending in a lamina apicalis medially divided ( Figs 5 A, C ; 11 A, C Pinto-da-Rocha 1995, figs 5; 7). Presence of two titillators with their apical edges dorsally projected, the internal surface of titillators is covered by small digitiform projections ( Figs 5 A ; 11 A ; Pinto-da-Rocha 1995, fig. 5). Stenostygnus can be distinguished from the other Stenostygninae genera by the absence of the male sexually dimorphic characteristics of swollen chelicerae and metatarsus III enlarged. Also, by the presence of a pars distalis with a lamina apicalis medially divided and two titillators with their apical edges dorsally twisted and covered by digitiform projections on the internal surface. In addition, Stenostygnus (as well as Bidoma Šilhavý, 1973 , and Decuella Avram, 1977 ) also differs by the absence of a median longitudinal groove in area I. Stenostygnus can be distinguished from Bidoma by the absence of a tubercle on the eye mounds connected with the opposite tubercle located on the anterior margin of area I ( Figs 2 A vs Šilhavý 1973, figs 71, 74). Differentially, Stenostygnus and Manahunca Šilhavý, 1973 have the mesotergal areas and free tergites without spiniform apophyses. However, Stenostygnus can be easily differentiated from Manahunca by lacking tubercles, being armed only with scarce small granules or smooth.

Species included. Stenostygnus huberi spec. nov., Stenostygnus martensi spec. nov., Stenostygnus pusio .

Figures

FIGURES 2A–F. Stenostygnus martensi spec. nov., male (paratype, MNRJ 2692), habitus (A dorsal, B ventral, C detail of sternum, D detail of spiracle, E lateral, F detail of ozopore). Scale bars: A, B, E= 500µm; C= 200 µm; D= 50 µm; F= 100µm.

FIGURES 3A–F. Stenostygnus martensi spec. nov., male (paratype, MNRJ 2692). A–C Right chelicera (A ectal, B frontal, C detail of fingers). D–F Right pedipalp (D mesal, E detail of tibia and tarsus, F detail of femur). Scale bars: A, B, E= 200 µm; C, F= 100 µm; D= 500 µm.

FIGURES 5A–G. Stenostygnus martensi spec. nov., male (paratype, MNRJ 2692), penis (A, E dorsal, B, F lateral, C, G ventral, D detail of conductor and stylus). CO—conductor. LA—lamina apicalis. SO—stylus opening of ductus ejaculatorius. ST—stylus. Ti—Titillator. Scale bars:A= 50 µm; B, C, E-G= 100 µm; D= 20 µm. Stylus in green, conductors in pink and capsula externa in blue (For interpretation of the references to colour the reader is referred to the pdf version of this article).

FIGURES 6A–D. Stenostygnus martensi spec. nov., sexual dimorphism (A–B female paratype, MNRJ 2692, C–D holotype male, MIZA 0103460). A, C Dorsal view. B, D Detail of tibia. Scale bars: A, C= 2 mm; B, D= 500 µm.

FIGURES 8A–F. Stenostygnus huberi spec. nov., male (ss) (paratype, MNRJ 2429), habitus (A dorsal, B ventral, C detail of sternum, D detail of spiracle, E lateral, F detail of ozopore). Scale bars: A = 1 mm; B, E= 500 µm; C, F= 100 µm; D= 20 µm.

FIGURES 11A–G. Stenostygnus huberi spec. nov., penis (A–B male (ss) paratype, MNRJ 2429; C male (ss), paratype, MACN 41020; D–G holotype male (α), MIZA 0103461). A, D Dorsal view. B, E, G Lateral view (G with detail of stylus and conduc- tors). C, F Ventral view. LA—lamina apicalis. Ti—Titillator. Scale bars: 100 µm. Stylus in green, conductors in pink and capsula externa in blue (For interpretation of the references to colour the reader is referred to the pdf version of this article).

FIGURES 12A–F. Stenostygnus huberi spec. nov., sexual dimorphism (A–B female paratype, MNRJ 2429; C–D male (ss) paratype, MACN 41020; E–F (holotype male (α), MIZA 0103461), A, C, E Dorsal view. B, D, F Detail of patella. Scale bars: A, C, E= 2 mm; B, F= 200 µm; D= 500 µm