Otostigmus ruficeps Pocock, 1890

Joshi, Jahnavi & Edgecombe, Gregory D., 2013, Revision of the scolopendrid centipede Digitipes Attems, 1930, from India (Chilopoda: Scolopendromorpha): reconciling molecular and morphological estimates of species diversity, Zootaxa 3626 (1), pp. 99-145 : 119-122

Otostigmus ruficeps Pocock, 1890

( Figs 68–77 )

Otostigmus ruficeps Pocock, 1890: 247 , pl. 12, figs 2–2b. Otostigmus ruficeps . Lewis, 1996: 828, figs 20–23.

Digitipes putative species 9. Joshi and Karanth, 2012: figs 2, 3.

Diagnosis. Otostigmus with 21 elongate antennal articles, the basal 2–2.5 glabrous dorsally; forcipular tooth plates with 4+4 large teeth, small (fifth) inner tooth variably present; four teeth along margin of forcipular trochanteroprefemoral process; longitudinal median depression on posterior half of tergite of ultimate leg-bearing segment; two apical spines on coxopleural process, dorsal spine rarely present; lateral spine mostly lacking; two tarsal spurs on legs 1–4 to 1–19 (usually 1–17 to 1–19), one on leg 20; a tibial spur typically on legs 1–6 to 1–8; ultimate leg prefemur with 2 VM spines and 2–3 VL spines.

Material examined. CES 091013, from Pushpagiri Reserve Forest, Karnataka; CES 091048, from Parambikulam Tiger Reserve, Kerala; CES 091327, CES 091330, CES 091331, from Siruvani Reserve Forests, Kerala; CES 091021, from Bisale Ghat Reserve Forests, Karanataka; CES 091342, from Achankovil Reserve Forest, Kerala. All leg. J. Joshi, 2009.

Description. [Based on CES material from Karnataka and Kerala] Length to 36 mm. 21 antennal articles apart from one specimen with 17; basal 2–2.5 articles glabrous dorsally, usually 2.2–2.33, one specimen with third article glabrous apart from its distal half on inner side only. Longitudinal median furrow on anterior 25% of cephalic plate.

Cephalic plate and T1 brown or orange-brown except for blue anterior part of cephalic plate; TT2 or 3 to 21 mostly blue or with brown pigment increasing from ca T12; basal glabrous part of antenna pale blue.

Forcipular coxosternal tooth plates with four main teeth ( Figs 69, 70 ), inner two usually grouped together, outer tooth smaller than the inner three; tiny fifth tooth at inner margin on one side of two specimens. Trochanteroprefemoral process with three ( Fig. 70 ) or usually four teeth, arranged as distal tooth and two teeth along inner margin or four uniform teeth.

Second maxillary claw with slender, needle-like accessory spurs. Article 2 of telopodite bearing a slender spine distally.

Tergites with paramedian sutures complete from TT5 to 7; tergites marginate from 6 to 8. Tergites smooth, lacking median ridge or keels ( Fig. 77 ). Sternites with paramedian sutures confined to anterior part.

Two tarsal spurs on legs 1–17 to 1–19 except for one individual with two spurs on legs 1–4 only; one tarsal spur on leg 20; a tibial spur on legs 1–6, 1–7 or 1–8 except for one individual with spur on leg 1 only (same specimen as with restricted number of legs with two tarsal spurs). A femoral spur variably present on leg 1 only.

Tergite of ultimate leg-bearing segment with nearly parallel lateral margins, usually with straight posterolateral margins, pointed posteromedially ( Fig. 72 ); one specimen with a more transverse posterior margin; shallow longitudinal median depression on posterior half of tergite. Sternite of ultimate leg-bearing segment with sides converging relatively strongly posteriorly, nearly straight, posterior margin variably concave ( Fig. 73 ).

Coxopleural process moderately long, not obviously inflected from posterolateral margin of coxopleuron in ventral view ( Fig. 73 ), with two apical spines except for one individual with three apical spines on one side; lateral spine lacking except for one individual with one lateral spine on one side. Pores relatively dense; non-porose area on coxopleural process long, narrow, reaching posterior margin of sternite of ultimate leg-bearing segment ( Fig. 73 ). Ultimate leg prefemoral spines: VL 2 or 3, VM 2, DM 0 ( Fig. 74 ). Ultimate leg tarsus 1 1.7–2 times length of tarsus 2; pretarsus with pair of short accessory claws.

Discussion. This species was resolved as sister species to all other Indian Digitipes in the molecular phylogeny (Joshi and Karanth 2012), and the clade that unites the other species had strong node support (posterior probability 1, bootstrap support 100%). No specimens have a distomedial process on the femur of the ultimate leg ( Fig. 75 ), rendering assignment to Digitipes unproven. Most specimens of this species differ from Indian Digitipes in having two tarsal spurs and a tibial spur on much more posterior segments than in the other species (i.e., two tarsal spurs to legs 17–19 versus not further than to leg 14, and usually confined to legs 1–3 or 1–4; a tibial spur to legs 6–8 versus confined to leg 1 only). We note, however, that a specimen nested within the molecular phylogeny for the species (CES 091342) has two tarsal spurs only as far as leg 4 and a tibial spur on leg 1 only. Other characters that differ from Indian Digitipes are the non-exact transition to glabrous antennal articles (a partial glabrous extent is seen on article 3 versus an abrupt transition between articles 2 and 3, 3 and 4, or 4 and 5 in all Indian Digitipes studied here), and the longitudinal depression on the tergite of the ultimate leg-bearing segment. These characters are shared by Otostigmus ruficeps Pocock, 1890 , until now known only from its holotype, from Madras. Comparison of the holotype (NHM 1890.1.23.22) and our collections strongly indicates conspecificity, and the species diagnosis is revised above based on shared characters that provide a distinctive combination within Otostigmus (Otostigmus) . Characters of the ultimate leg are added to the diagnosis based on our material because the holotype lacked ultimate legs even at the time of its description.

Lewis (1996) redescribed the holotype of O. ruficeps and noted that the species keys out to Otostigmus multidens (Haase, 1887) using the standard keys (Kraepelin 1903; Attems 1930b). He noted that the number of forcipular teeth (5+5) in the holotype of O. ruficeps is at the extremity of the range observed in O. multidens but concluded that no clear distinction could be made between the two species, and proposed the junior synonymy of O. ruficeps . The present collections suggest that the small inner tooth on the tooth plates of the holotype relates to variability within a species that more commonly has 4+4 large teeth. Redescription of O. multidens by Lewis (2001) and examination of material of that species from Thailand, Vietnam and New Guinea lead us to maintain O. ruficeps as a valid species from India. O. multidens has small teeth interpolated between some of the large teeth on the tooth plates, and has tibial spurs extending as far posteriorly as legs 16–18 (versus legs 1–7 in the holotype of O. ruficeps and legs 1–6, 7 or 8 in our specimens). These differences are consistent with separate species, although the shared presence of four teeth on the forcipular trochanteroprefemoral process and a longitudinal depression on the tergite of the ultimate leg-bearing segment suggest that O. ruficeps and O. multidens are closely related.

Figures

FIGURES 68 – 73. Otostigmus ruficeps Pocock, 1890. 68. Cephalic plate and T 1, dorsal view, CES 091013, scale = 2 mm. 69. Forcipular segment, ventral view, CES 091048, scale = 1 mm. 70. Tooth plates, ventral view, CES 001013, scale = 1 mm. 71. Coxopleuron, lateral view, CES 091330, scale = 1 mm. 72. Tergite of ultimate leg-bearing segment, dorsal view, CES 091330, scale = 2 mm. 73. Coxopleuron and sternite of ultimate leg-bearing segment, ventral view, CES 091330, scale = 1 mm.

FIGURES 74 – 77. Otostigmus ruficeps Pocock, 1890. 74. Ultimate leg prefemur, ventral view, CES 091327, scale = 1 mm. 75. Ultimate leg femur, dorsal view, CES 091327, scale = 1 mm. 76. Spiracle on segment 3, CES 091013, scale = 0.5 mm. 77. TT 17 – 20, dorsal view, CES 08960, scale = 1 mm.