Digitipes Attems, 1930

Schileyko, Arkady A., Vahtera, Varpu & Edgecombe, Gregory D., 2020, An overview of the extant genera and subgenera of the order Scolopendromorpha (Chilopoda): a new identification key and updated diagnoses, Zootaxa 4825 (1), pp. 1-64 : 45-46

(!) Digitipes Attems, 1930

Figs 89–92

Type species. Digitipes verdascens Attems, 1930 (by monotypy).

Diagnosis. Median tooth of labrum very small, much shorter than lateral labral lobes ( Fig. 90 ). Forcipular toothplates present, trochantero-prefemur with well-developed process ( Fig. 91 ). Rarely some posterior tergites with well-developed longitudinal keels (for example in D. barnabasi Jangi and Dass, 1984 ; see fig. 10 of Joshi & Edgecombe 2013), usually these keels lacking or very poorly developed. Sternites may bear paramedian sutures (or sulci) as well as a median longitudinal sulcus and posterior depression ( Fig. 92 ). LBS 7 lacking spiracles, the latter with atrium. Legs with tarsal spur(s), the only exception— D. nudus (Pocock, 1890) (former D. periyarensis Joshi & Edgecombe, 2013 ) (see below). Coxopleural process from short to moderately long, with apical spines. Ultimate prefemur with spines but lacking corner spine, pretarsus well-developed. Femur of males with well-developed (but incomplete) medial longitudinal depression leading to an obtuse conical distomedial process ( Fig. 89 ) that bears scattered setae (see also figs 9, 21, 42, 54 in Siriwut et al. 2015).

Number of species. 9 ( Edgecombe & Bonato 2011: 402), 11 ( Bonato et al. 2016), 10 ( Siriwut et al. 2015: 76).

Sexual dimorphism. Present.

Remarks. Treated as a genus in Edgecombe & Bonato (2011: 402), Joshi & Edgecombe (2013: 99), Vahtera et al. (2013: 594), Joshi & Edgecombe (2018: 1318), Joshi & Edgecombe (2019: 3). Siriwut et al. (2015) considered it as a genus but wrote (p. 83): “Within the Otostigminae , members of Digitipes were separated into two clades”. Joshi & Edgecombe (2017) analyzed in detail the Indian species of this genus. More densely sampled molecular phylogenies by Siriwut et al. (2018) and Joshi et al. (2020) depicted Digitipes as monophyletic apart from the nesting of Otostigmus nudus Pocock, 1890 (former D. periyarensis ) within it. However, more material should be studied (using both traditional and molecular approaches) to be sure to which genus (Otistigmus or Digitipes ) this species belongs.

An incomplete (it lacks some posterior LBS) specimen of Digitipes sp. (Rc 7565 from E Gabon) has a very small median tooth of the labrum ( Fig. 90 ), which is also characteristic within Otostigminae for Sterropristes + Edentistoma (see below), and an unusually wide process of the forcipular trochantero-prefemur ( Fig. 91 ). In addition, this specimen has no legs with tarsal spurs (a very rare condition in Otostigminae ), so it is similar to the former Digitipes periyarensis in this (and some other) morphological aspects.

An obtuse conical distomedial process of the femur of male Digitipes is (with the exception of being spineless) similar to the standard corner spine of the ultimate prefemur of Scolopendridae .

We consider this genus as problematic since the femoral characters are restricted to mature males such that the females of Digitipes cannot be morphologically separated from those of Otostigmus (Otostigmus) . In addition, “Specimens that possess the femoral process make up a small percentage of our total sample of Digitipes ” ( Joshi & Edgecombe 2013: 101). Analyzing the monophyly of Digitipes Vahtera et al. (2013: 595) wrote: “… the clade is sensitive to parameter set variation as it is resolved as monophyletic only under two of the six explored parameter sets”, although the data of Siriwut at al. (2018) and Joshi et al. (2020) strengthened the case for monophyly using more species.

All diagnostic features of Digitipes listed by Joshi & Edgecombe (2013:100) except for the male’s longitudinal groove and distomedial process of the ultimate femur are shared by all representatives of the nominotypical subgenus of Otostigmus . The “composite description” of Digitipes provided by Siriwut at al. (2015: 75) also perfectly fits for Otostigmus (Otostigmus) , apart from the aforementioned male characters. Taking into consideration the virtual morphological identity of these two genera, and the fact that the monophyly of Digitipes is not well supported by the morphological data, we consider this genus to require further investigation.

Figures

FIGURES 89–96. Digitipes coonoorensis Jangi & Dass, 1984; Male CES 091088 89 femur of right ultimate leg medially; Digitipes sp.; Ad. Rc 7565 90 clypeal part of head ventrally 91 forcipular segment ventrally 92 LBS 13–15 ventrally; Otostigmus (O.) multidens nordicus Schileyko, 1995; Ad. Rc 6545 93 LBS 21 ventrally; Ad. Rc 6747 94 anterior part of head ventrally; Otostigmus (O.) astenus (Kohlrausch, 1881); MCZ DNA 102463 95 pretarsus of maxilla 2; Sad. Rc 7507 96 forcipular segment ventrally; (ap)—apical spines of coxopleural process, (as)—accessory spines, (bs)—basal suture of forcipular toothplate, (cl)—clypeus, (cx)—coxopleuron, (df)—conical distomedial process of ultimate femur, (f)—ultimate femur, (l)—labrum, (lc)—lateral spine of coxopleural process, (lsc)—sternal median longitudinal sulcus, (md)—medial longitudinal depression of ultimate femur, (p2)—pretarsus of maxilla 2, (pd)—sternal posterior depression, (pr)—trochantero-prefemoral process, (psl)—sternal paramedian sulci, (tp)—forcipular tooth-plate, (ust)—ultimate sternite.