Otostigmus (Parotostigmus) casus Chamberlin, 1914

Chagas-Jr, Amazonas, 2016, A systematic appraisal of the types of ten species of Otostigmus (Parotostigmus) (Scolopendromorpha, Scolopendridae, Otostigminae), Zootaxa 4147 (1), pp. 36-58 : 38-39

Otostigmus (Parotostigmus) casus Chamberlin, 1914

( Figures 5–10 )

Otostigmus casus Chamberlin, 1914: 177 ;

Otostigmus (Parotostigmus) casus Attems, 1930: 164 ; Bücherl, 1940: 232; 1942: 63; 1974: 111.

Type material examined. Holotype MCZ IZ no.1481 (14278), Brazil, Mato Grosso, Madeira-Mamore, Railroad Camp 39, “Expedition: Stanford Expedition to Brazil 1911, Coll: W.M. Mann, 1911 ( Figs 5–6 ).

Redescription. Length: 57 mm from the anterior margin of the cephalic plate to the posterior margin of tergite 21. Antennae with 17 articles, two basal articles glabrous. Cephalic plate smooth, without sutures and depressions, but with median sulcus anteriorly ( Fig. 7 ). Coxosternal tooth-plates, wider than long with 4+4 teeth and a strong seta on each plate. Coxosternite with a transverse suture at the base of the tooth-plates; this suture is laterally bifurcate (not described) ( Fig. 8 ). Margin of the forcipular trochanteroprefemoral process with one small medial denticle.

Tergites 1–6 smooth, from tergites 7–21 with tubercles, the number increasing gradually; the posterior tergites are densely tuberculate; tergites 12–20 more tuberculate laterally (keels and general surface scabrous). Tergites 5– 20 with complete paramedian sutures. Tergites 7–20 with a low median longitudinal keel (5 or 6); tergites 7–21 marginate (depressed from the fifth caudad, leaving the lateral margin distinctly elevated especially in the middle and caudal regions, but true margination only on tergite 21). Tergite 21 convex, its posterior margin with a shallow median longitudinal depression (last dorsal plate with the posterior edge moderately bowed out caudad and mesially truncate) ( Fig. 9 ).

Sternites 2–18 with a rounded depression in the center, those of sternites 2 and 3 very shallow;(with three pitlike depressions arranged in a triangle as usual; there are also three other depressions along the caudal border). Sternite 21 with posterior margin concave (narrowed caudad, the sides convex at the anterior ends, but straight and meeting in the middle at a slightly reentrant angle). Sternites without sutures. Coxopleuron without spines. Porefield covers almost all the coxopleuron, only its posterior end poreless ( Fig. 10 ).

Legs 1 with one tibial and two tarsal spurs in the tarsus; legs 2, 3, 6, 9, 17, and 18 with one tarsal spur (2 to 18 with a single tarsal spur). Ultimate legs missing (19 to 21 pairs of legs unknown).

Remarks. Chagas-Jr (2012) considered O. casus as one of the most problematic Brazilian Otostigmus to identify. His conclusion was preliminary, since he had not yet examined the type of O. casus . Even so, he compared the original description of O. casus with other Brazilian Otostigmus and observed that O. casus resembles O. tidius in the presence of both short paramedian sutures on the sternites and two tarsal spurs at legs 1–8 ( Chagas-Jr 2012). After examining the type of O. casus , I noticed that there are no short paramedian sutures on sternites, and two tarsal spurs at legs 1 only. Besides, both the dorsal integument and body size in O. casus are more similar to the types of O. suitius , O. rex and O. samacus than to O. tidius . In O. casus , O. rex and O. suitius the tergites have complete paramedian sutures from tergites 5–20, in O. samacus from tergites 4–20. There is margination from tergites 7–21 in O. casus and O. suitius , and from tergites 6–21 in O. rex and O. samacus . The body length of O. casus , O. rex and O. suitius varies from 55 to 78 mm, and in O. tidius from 13 to 22 mm. The holotype of O. tidius was not found in the myriapodogical collection of the Museum of Comparative Zoology, but Chagas-Jr (2012) examined ten specimens of O. tidius from the states of Tocantins, Mato Grosso, Goiás, and Distrito Federal, Brazil . As with in the case of O. casus , O. rex and O. suitius , which were collected from the same locality in northwestern Mato Grosso state, have been described in the same work, and share characters in common, O. casus is here considered as a junior synonym of O. suitius .

Figures

FIGURES 5 – 6. Otostigmus (P.) casus. Holotype Holotype MCZ IZ no. 1481 (14278). 5. Habitus, (dorsal view). 6. Habitus, (ventral view). Scale bars 10 mm.

FIGURES 7 – 10. Otostigmus (P.) casus. Holotype Holotype MCZ IZ no. 1481 (14278). 7. Cephalic plate and tergites 1 – 2. 8. Head, forcipular segment and sternites 1 – 2. 9. Tergites of antepenult, penultimate and ultimate leg-bearing segments. 10. Sternites of antepenult, penultimate and ultimate leg-bearing segments and coxopleuron. Scale bars 1 mm.