Otostigmus (Parotostigmus) mesethus Chamberlin, 1957

Chagas-Jr, Amazonas & Souza, Emerson Marques, 2024, A review of the types of some Otostigmus (Parotostigmus) (Scolopendromorpha, Scolopendridae, Otostigminae) of the Andes mountain range, Zootaxa 5529 (3), pp. 436-460 : 448-451

Otostigmus (Parotostigmus) mesethus Chamberlin, 1957

Figs 31–40

Type material examined: Lectotype male (here designated) and paralectotype female CAS 15216 (12-164), Ecuador, 6-12 mi. SW. Baños, N. slope Mt. Tungurahua, 13.ii.1955.

Additional material examined: Ecuador, NMNH 31472 , 2 males ; FSCA, 1 specimen, Limoncocha , xi.1964, PW. Hermann ; MCZ 02138 , 1 male and 5 females, 10 Km N. Alausi, 2700 m, 22.xi.1965 ; NMNH 31472 , 2 specimen, Prov. Tungunrahua , Rio Blanco, 15.ix.1937, Wm. Clarke .

Redescription of lectotype male. Length: 45 mm from anterior margin of cephalic plate to posterior margin of tergite 21 ( Fig. 31 ). Antennae with 17 articles (left) and 13 (right); first two basal and basal part of third glabrous [not described]. Cephalic plate smooth, without sutures and depressions, but with median sulcus [very short] in anterior part (almost slightly concave) [not described] ( Fig. 33 ). Coxosternal tooth-plates wider than long, with 4+4 teeth, and a long bristle [not described] ( Fig. 34 ); coxosternite with a short paired sutures at base of tooth-plates, this suture is bifurcate in the sides and with a short median longitudinal suture [not described). Trochanteroprefemoral process large, with the margin with two or three short tubercles and its tip pointed [not described]. Tergites 6–20 with complete paramedian sutures; tergites 3–5 with very short incomplete paramedian sutures in the anterior and posterior margin; tergite 5–21 with a shallow median longitudinal keel; tergites 1–3 smooth; tergites 4–21 rugose, the rugosity increasing from anterior to posterior tergites; tergites 7–21 margined; posterior margin of tergite 21 very slightly angulate, with a shallow median longitudinal depression in posterior margin ( Fig. 35 ); tergite 21 with a short median longitudinal keel. Sternites 4–17 with incomplete paramedian sutures in the anterior margin; sternites 4–19 with two small rounded depressions arranged horizontally in the center; sternite 20 slightly concave in the sides, but straight in the middle; lateral distal side of sternite 20 very short pronounced. Sternite 21 with posterior margin straight, shorter than precedent ( Fig. 36 ), converging posteriorly, with a shallow median longitudinal depression. Coxopleuron without spines. Pore-field covers almost entire coxopleuron, only the posterior end poreless. Posterior part of coxopleuron truncate, with a very short protuberance. Leg 1 with one femoral and one tibial spur; legs 1–3 with two tarsal spurs; legs 4–19 with one tarsal spur, 20 and 21 without [legs 4 and 5 missed]. Coxae 19 with a very short protuberance; coxae 20 with a short appendix positioned posteriorly ( Fig. 36 ). Prefemur of ultimate pair of legs without spines, with a digitiform appendix almost the same length as the prefemur ( Fig. 35 ); digitiform appendix dorsoventrally flattened and with a tuft of hair at its dorsal tip.

Redescription of paralectotype female. Length: 44 mm from anterior margin of cephalic plate to posterior margin of tergite 21 ( Fig. 32 ). Antennae with 17 articles (right) and 10 (left); first two basal and the basal part of third glabrous. Cephalic plate smooth, without sutures and depressions, but with median sulcus [very short)] in anterior part (almost slightly concave) ( Fig. 37 ). Coxosternal tooth plates with the same length and width, with 4+4 teeth, and a long bristle ( Fig. 38 ); coxosternite with a short paired sutures at base of tooth-plates, this suture is bifurcate in the sides and a short median longitudinal suture [not described]. Trochanteroprefemoral process large, with the margin with two or three short tubercles and its tip pointed. Tergites 6–20 with complete paramedian sutures; tergites 3–5 with very short incomplete paramedian sutures in the anterior and posterior margin; tergite 9– 21 with a shallow median longitudinal keel; tergites 1–12 smooth; tergites 12–21 quite rugose, rugosity increasing in the posterior tergites, but less than in holotype; tergites 9–21 margined; posterior margin of tergite 21 very slightly angulate, without a shallow median longitudinal depression in the posterior margin ( Fig. 39 ); tergite 21 with a short median longitudinal keel. Sternites 11–17 with incomplete paramedian sutures in the anterior margin; sternites 4–17 with two small, rounded depressions arranged horizontally in the center; posterior margin of sternite 20 straight. Sternite 21 with posterior margin straight, shorter than precedent, converging posteriorly, with a shallow median longitudinal depression ( Fig. 40 ). Coxopleuron without spines. Pore-field covers almost entire coxopleuron, only the posterior end poreless. Posterior part of coxopleuron truncate. Leg 1 with one tibial spur; legs 1–4 with two tarsal spurs; legs 5–19 with one tarsal spur, 20 and 21 without. Coxae 19 without an appendix; coxae 20 with a very short appendix positioned posteriorly ( Fig 40 ), shorter than in holotype.

Prefemur of ultimate pair of legs without spines and any kind of sexual dimorphism (appendix).

Remarks. The description of the types of O. mesethus is very brief compared to the description of some other Otostigmus species described by Chamberlin (1957). He merely stated that the species is closely related to O. lavanus syn. nov. and that O. mesethus differed from this species by the presence of two tarsal spurs on legs 1–3, the posterior margin of sternite 21 being straight in the holotype, and the mesocaudal corner of coxae 20 being rounded instead of angular. He also mentioned that due to the lack of a series of specimens, it was difficult to determine some differences in certain characters that could be related to the age of the specimen. He did not specify which character he was referring to, but given the description, it appears that he was referring to the appendages of coxae 19 and 20, and the digitiform appendix on the prefemur of the ultimate legs. The appendages of coxae 19 and 20 in O. mesethus are much shorter than the appendages of coxae 19 and 20 in O. insignis , O. lavanus syn. nov., and O. silvestrii intermedius . However, the length of the digitiform appendix on the prefemur of the ultimate legs of O. mesethus is almost as long as that of O. silvestrii and slightly longer than that of O. parvior syn. nov. The shorter appendages on coxae 20 present in O. mesethus , O. silvestrii , and O. parvior syn. nov. could be a characteristic of females of these three species. However, the appendages of female O. mesethus are much shorter, and the prefemur of leg 21 does not have a digitiform appendix. Therefore, O. mesethus is considered a valid species.

Figures

FIGURES 31–32. Otostigmus (P.) mesethus Chamberlin, 1957. Lectotype CAS 15216 (12-164), male. 31. General view dorsally. 32. Allotype CAS 15216 (12-164), General views dorsal and ventral.

FIGURES 33–36. Otostigmus (P.) mesethus Chamberlin, 1957. Lectotype CAS 15216 (12-164), male. 33. Cephalic plate and tergites 1 and 2, dorsally. 34. Head, forcipular segment, and sternites 1 and 2, ventrally. 35. Tergites 20 and 21, dorsally. 36. Sternites 20 and 21, ventrally.

FIGURES 37–40. Otostigmus (P.) mesethus Chamberlin, 1957. Paralectotype CAS 15216 (12-164), female. 37. Cephalic plate and tergites 1 and 2, dorsally. 38. Head, forcipular segment, and sternites 1 and 2, ventrally. 39. Tergites 20 and 21, dorsally. 40. Sternites 20 and 21, ventrally.