Otostigmus (Parotostigmus) coltellus, Simaiakis & Edgecombe, 2013

Simaiakis, Stylianos Michail & Edgecombe, Gregory D., 2013, Scolopendromorph centipedes (Chilopoda: Scolopendromorpha) in the Natural History Museum (London): A review of the hitherto unidentified species collected in Africa, with remarks on taxonomy and distribution, and a new species of Otostigmus (Parotostigmus), Zootaxa 3734 (2), pp. 169-198 : 177-179

8. Otostigmus (Parotostigmus) coltellus n. sp.

( Figs 9–14 )

Otostigmus inermis Karsch, 1884 [non Porat, 1876] [partim]

Otostigma productum Karsch, 1888 [partim]

Diagnosis. Otostigmus (Parostostigmus) with four glabrous antennal articles; short, blade-like tooth plate lacking teeth, base of tooth plate set off by transverse suture; paramedian sutures complete from T3 or usually T4; short coxopleural process with two small apical spines.

Type material. Holotype ( Figs 9, 10, 12, 13 ): Gulf of Guinea: Zampalma, São Tomé Isl. [ Democratic Republic of São Tomé and Principe], 13/9/1949, leg. I.L.J. Galbraith, BMNH 1950.3.7.127-136 ( Fig. 8 ); paratype female from same collection . Paratype ( Figs 11, 14 ): Gulf of Guinea: São Tomé Isl., West Africa , 1932, Percy Sladen Memorial and Godman Exploration, leg. W.H. T. Tams, 1 ex., BMNH 1933.8 .30.239. ( Fig. 8 ) .

Description. Length to 78 mm (holotype).

Cephalic plate and tergites pale brown to chestnut brown ( Fig. 9 ); legs orange-brown.

Antenna extending back to T5 , with 17 articles in types (16 articles in ZMB 927 ), the basal four glabrous ( Fig. 10 ). Cephalic plate punctate, variably with a pair of longitudinal depressions posteriorly .

Coxosternal tooth plates several times wider than long; anterior margin of tooth plate straight, adentate, gently inclined laterally for most of its width, expanding at its lateral corner to from a blunt bulge ( Figs 11, 12 ). Single hyaline seta near midline of toothplate, inserting at boundary of strongly pigmented margin. Trochanteroprefemoral process a sclerotized blade, lacking distinct teeth ( Figs 11, 12 ).

Second maxillary telopodite with a pretarsal accessory spur; dorsal spine on distal part of article 2.

Tergites smooth, lacking keels or rugosity. Paramedian sutures continuous from TT 3 or 4–20; mostly with incomplete sutures extending about half length of T3 . Margination complete on TT 19–21, incomplete from TT 14– 15. Sternites with continuous paramedian sutures to S19, lacking on S20 .

Legs 1 and 2 with two tarsal spurs; legs 3 to 16, 17, 18 or 19 with one tarsal spur, lacking on leg 20; all legs lacking tibial spurs apart from leg 1 (right leg only) in ZMB 927.

Spiracles elliptical, with strongly humped atrial floor.

Tergite of ultimate leg-bearing segment with broadly V-shaped posterior margin, lacking median depression. Sternite of ultimate leg-bearing segment narrowing posteriorly, with nearly straight lateral and posterior margins.

Coxpleural process short, with two small apical spines in types (one in ZMB 927) but lacking dorsal or lateral spines. Pore field extends to dorsal and posterior margins of coxopleuron, with only a short, narrow pore-free band at coxopleural process ( Figs 13, 14 ).

Ultimate leg relatively slender, relative lengths of podomeres in the ratio prefemur 1, femur 1, tibia 0.88, tarsus 1 0.73, tarsus 2 0.39, pretarsus 0.22; prefemur of even width (in dorsal view) along its length, width distally about one-third its length. Prefemur lacking spines apart from one mid-ventral spine near midlength in ZMB 927. Ultimate leg pretarsus with accessory claws.

Etymology. Coltello, Italian for knife, with reference to the blade-like tooth plates.

General distribution. West-Central Tropical Africa: Gulf of Guinea ( São Tomé, Rolas) (ST).

Discussion. The type material is from the island of Säo Tomé; a conspecific specimen (ZMB 927; Museum für Naturkunde, Berlin) from the island of Rolas is a syntype of Otostigmus (Parotostigmus) productus Karsch, 1888 but is excluded from that species with the designation of a lectotype below.

Compared to all other African O. ( Parotostigmus ), this species is readily distinguished by its adentate tooth plates. The most similar species, O. (P.). productus Karsch , also occurs on São Tomé, and the two taxa share some character states that, in combination, separate them from other African O. ( Parotostigmus ). These include 17 antennal articles, four of which are glabrous (versus 2–2.5 in other species), complete paramedian sutures from TT3 or 4, complete paramedian sutures on the sternites, and a pair of coxopleural apical spines. The uniquely adentate tooth plates of O. (P.) coltellus are the same in the four known specimens of the species and this difference from O. (P.) productus cannot be attributed to wear, particularly because the sutures defining the base of the tooth plate are distinct from those of O. (P.) productus . In the latter species, the relatively long tooth plates are set off by oblique sutures (for further details see figures in O. (P.) productus ), whereas the suture at the base of the tooth plate in O. (P.) coltellus is approximately transverse (see Figs 11, 12 ). As well, the position of the single hyaline seta on each tooth plate is a reliable marker of the boundary between the sclerotized margin of the tooth plate and its basal plate. The two species are also readily distinguished by the shape of the coxopleural process, being shorter and less slender in O. (P.) coltellus . These two species co-occur in the collection from Zampalma that includes the holotype of O. (P.) coltellus . Although a marked size difference separates the two (large) specimens of O. (P.) coltellus from the nine smaller specimens of O. (P.) productus , morphological differences cannot be attributed to changes with growth because the smaller paratype of O. (P.) coltellus (BMNH 1933.8.30.239) is scarcely larger than the Zalpalma specimens of O. (P.) productus , yet both species exhibit their typical characters of the tooth plates and coxopleural process.

Figures

FIGURE 8. Otostigmus (Otostigmus) cuneiventris, O. (Parotostigmus) coltellus n. sp., O. (P.) gemmifer and O. (P.) productus, distribution records of specimens from Africa housed in the NHM collection.

FIGURES 9–14. Otostigmus (Parotostigmus) coltellus n. sp. Holotype BMNH 1950.3.7.127-136 (São Tomé), except figs 11, 14, paratype female from same collection: Figure 9, posterior part of cephalic plate and TT1–4, dorsal view, scale bar 2 mm; Figure 10, left antenna, dorsal view, scale bar 1 mm; Figure 11, forcipular segment, ventral view, scale bar 1 mm; Figure 12, tooth plates, scale bar 0.5 mm; Figure 13, coxopleuron and sternite of ultimate leg-bearing segment, ventral view, scale bar 1 mm; Figure 14, coxopleuron and sternite of ultimate leg-bearing segment, ventral view, scale bar 1 mm.