Digitipes Attems 1930
Creators: name: Lewis, John G. E.
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Chilopoda
Scolopendromorpha
Scolopendridae
Digitipes

description: Genus Digitipes Attems, 1930
Introductory remarks. Digitipes is considered here, as two of the putative eleven species of the genus are very similar to two Otostigmus species discussed in this paper.
Attems (1930a, b) characterised the genus by the presence of a process on the femur of the ultimate legs in males and the second maxillary pretarsus without accessory spines and without a spur on article 2 of the telopodite. Lewis (2004) pointed out that the accessory spines could be very rudimentary in some Otostigmus species and that the spur was absent in O. resrevatus Schileyko, 1995. Furthermore Chagas-Jr. et al. (2007) did not observe accessory spines or a spur on article 2 of the telopodite in seven South American species of Otostigmus (Parotostigmus) confirming that there is no justification in the separation of Digitipes from Otostigmus. Most recently, Joshi & Edgecombe (2013) showed that these characters were present in Indian Digitipes. They agreed that the two peculiarities of the second maxilla cited by Attems (1930a, b) as diagnostic for Digitipes are of no value for the generic concept if it is meant to encompass Indian species. See Joshi & Edgecombe (2013) for a full discussion of the matter.
Joshi & Edgecombe (2013) defined the genus as Otostigmini lacking spiracle on segment 7. Forcipular toothplates with four teeth, the inner two grouped. Coxopleural process with two apical spines, no dorsal spines, single lateral spine present or absent. Conical to subcyclindrical distomedial process on femur of ultimate leg in male, longitudinal furrow along medial surface of femur terminating on the process. However, they pointed out that apart from the characters of the male ultimate leg, these characters are shared by other species currently assigned to Otostigmus (Otostigmus) and this is true for all the species of Otostigmus considered here.
The African Digitipes species
(Table 3)
Of the three African species, Digitipes verdascens Attems, 1930, the type species, and D. reichardti (Kraepelin, 1903) have a distomedial process on the ultimate leg femur in the male but the sole specimen of D. krausi Dobroruka, 1968, lacks this process and was described as a female. Dobroruka assigned it to Digitipes as the second maxillary telopodite lacked pretarsal accessory spines and a spur on article 2, as he indicated in a table showing the characters of Digitipes. As noted above, these are of no value in distinguishing the genus from Otostigmus.
Digitipes krausi and the other two African species are similar in that only the tergite of the ultimate leg-bearing segment is marginate (this is also listed as a character of Digitipes by Dobroruka). However, it differs from them in other respects, resembling O. cuneiventris in the absence of sternite paramedian sutures and the presence of sternite depressions. In D. krausi there are three depressions (Dobroruka’s Fig. 16), closely resembling in size and arrangement the larger three in O. cuneiventris spm 1 from Mapanja, Cameroon (Fig. 52). It also differs from the other two Digitipes species in that the legs lack tarsal spurs and the presence of three rows spines on the prefemoral of the ultimate legs (VL 3, VM 2, DM 2) rather than two (Table 3). Its assignment to Digitipes thus rests solely on the fact that only the ultimate leg-bearing tergite is marginate but this character is seen in other Otostigmus species namely the North African O. spinicaudus (Newport, 1844) and the East African O. tanganjikus Verhoeff, 1941, both of which, unlike D. krausi, have most legs with tarsal spurs. I conclude that D. krausi is an Otostigmus and thus becomes Otostigmus krausi (Dobroruka, 1968) comb. nov.
The Indian Digitipes species
(Table 4)
Joshi & Edgecombe (2013) resolved the nine putative species of Indian Digitipes recognised by Joshi & Karanth (2012) in a molecular analysis as five Digitipes species and Otostigmus ruficeps Pocock, 1890. The Digitipes species are Jangi & Dass’s (1984) D. barnabasi, D. coonoorensis and D. indicus and two new species: D. jangii Joshi & Edgecombe (2013) and D. periyarensis. They showed that D. indicus is a junior subjective synonym of Arthrorhabdus jonesii Verhoeff, 1938, the combination becoming Digitipes jonesii (Verhoeff, 1938). They accepted the validity of D. pruthii Jangi & Dass, 1984, and D. chhotanii Jangi & Dass, 1984, although these species were known only from single specimens.
Joshi & Edgecombe (2013) noted that D. periyarensis (Joshi & Karanth’s (2012) Digitipes putative species 4 (PS4)) is very distinct morphologically from the other Indian species of the genus. Siriwut et al. (2015) noted that it is the most anomalous member of Digitipes morphologically and comparison can be made with species of Otostigmus in its robust, dorsally grooved ultimate legs. They added that the complete or nearly complete paramedian sutures on sternites in D. periyarensis should be emphasised because they resemble a condition found in other genera of Otostigminae (some species of Otostigmus) and that the membership of this species within Digitipes is heavily reliant on its molecular placement.
Siriwut et al. tabulated the taxonomic characters of the eleven species of the genus including their new species Digitipes kalewaensis Siriwut, Edgecombe & Panha, 2015 from Myanmar. The aggregated data for six Indian species are given in Table 4 together with D. kalewaensis, D. periyarensi s (the seventh Indian species) and O. nudus.
In addition to the almost complete sternite paramedian sutures and dorsally grooved ultimate legs Digitipes periyarensis differs from the other Indian species by the coxosternal tooth-plates being longer than wide rather than wider than long, the coxopleural pore-field not being widened anteriorly, the complete absence of tarsal, tibial and femoral spurs as opposed to femoral and tibial spurs on leg 1, two tarsal spurs on anterior legs and a single tarsal spur to leg 19 or 20 (no precise data on the distribution of tarsal spurs in D. chhotanii). The ultimate legs of the two specimens of D. periyarensis do not show the longitudinal groove along the medial surface of the femur or the conical to subcyclindrical distomedial femoral process present in the males of other Digitipes species and for this reason Joshi and Edgecombe regarded them as females.
Digitipes periyarensis is morphologically identical in almost all respects to O. nudus (see Table 4). The principle differences between them are the presence of a weak median keel on the tergites in O. nudus and in the greater development of the grooves and the presence of pits on the prefemur, femur and tibia of the ultimate legs of D. periyarensis. As shown above for O. geophilinus the degree of development of the grooves can vary considerably. These differences may be sexual or due to individual variation but do not seem sufficient to regard the two as separate species.
It is here proposed that D. periyarensis is a junior subjective synonym of O. nudus. The alternative would be to transfer the other morphologically similar Otostigmus species namely, the O. nudus, O. sulcipes, O. sutteri, O. geophilinus and possibly O. taeniatus and O. cuneiventris to Digitipes although no specimens show the distomedial process on the femur of the ultimate leg characteristic of mature male Digitipes and it seems very unlikely that all are females.
description: Published as part of Lewis, John G. E., 2015, On Verhoeff's Otostigmus subgenus Malaccopleurus, the nudus group of Otostigmus subgenus Otostigmus Porat, 1876, and Digitipes Attems, 1930, with a description of the foetus stadium larva in O. sulcipes Verhoeff, 1937, (Chilopoda: Scolopendromorpha: Scolopendridae), pp. 225-248 in Zootaxa 4039 (2) on pages 243-245, DOI: 10.11646/zootaxa.4039.2.2, http://zenodo.org/record/232674