Tetracentrosternus Pocock, 1895

Likhitrakarn, Natdanai, Golovatch, Sergei I. & Panha, Somsak, 2013, The millipede genus Tetracentrosternus Pocock, 1895 (Polydesmida, Paradoxosomatidae, Alogolykinae, Alogolykini), with a description of the first, new species from Thailand, ZooKeys 358, pp. 1-10 : 1-3

Genus Tetracentrosternus Pocock, 1895

Diagnosis.

Body medium-sized (ca 20-30 mm long, ca 2.0-3.2 mm wide), with 20 segments. Paraterga moderately to strongly developed. Sterna unmodified or with a cone near each coxa. Sternal lobe or cone(s) between ♂ coxae 4 present. First pair of ♂ legs with or without femoral adenostyles. At least some male legs with ventral brushes on tarsi, sometimes also on distal halves of tibiae.

Gonopod with a quite short, subcylindrical, distoventrally densely setose coxite; prefemoral (= setose) part of telopodite short to very short, a quarter or less as long as acropodite, delimited from extremely short femorite by a mesal sulcus, ridge or spine; femorite supporting a long, spiniform, sometimes deeply bipartite femoral process (fp) and a similarly long to longer, flagelliform solenomere (sl), both more or less clearly sheathed by a mesal fold in basal half of acropodite. The latter suberect to strongly unciform, distal quarter to third with or without evident processes, clearly fimbriate and/or fringed, often phylloid as well.

Type species.

Tetracentrosternus subspinosus Pocock, 1895; by monotypy.

Other species include Tetracentrosternus hoffmani Golovatch, 2013 and Tetracentrosternus theelorsuensis sp. n.

Remarks. Both Tetracentrosternus Pocock, 1895 and Tetracentrosternus subspinosus Pocock, 1895 were originally diagnosed and described too briefly to be readily recognizable. The species was based on a few specimens taken by L. Fea and E. W. Oates at Puepoli (900-1,200 m a.s.l.) and Bia-po, now Carin Cheba (1,000-1,200 m), both in Myanmar ( Pocock 1895, Thorell 1895). These two localities lie in the Karin Hills of southeastern Myanmar, in the Tenasserim Mountain Range adjacent to Thailand (Fig. 4).

The sole male of the species, from Puepoli and kept in the British Museum, was redescribed by Hoffman (1963) who designated it as lectotype. Hoffman was the first to provide clear illustrations of its gonopod structure, resulting in the establishment of a new tribe, Alogolykini , to encompass Tetracentrosternus , Alogolykus Attems, 1936 and Touranella Attems, 1937 ( Attems 1936, 1937, 1938). Jeekel (1965) redescribed this species in more detail not only from the lectotype, but also from the paralectotypes (from Carin Cheba) still housed in the Genoa Museum. He made new, even more accurate illustrations and a highly detailed redescription, fully accepting the tribe and adding thereto also Yuennannina Attems, 1936. A little later, Jeekel (1968) elevated the tribe Alogolykini to the status of a subfamily, Alogolykinae , adding thereto a new tribe, Polydrepanini . Jeekel transferred Touranella from Alogolykini to Polydrepanini , because the genus lacks adenostyles on the femora of the male first legs, as do the other constituent genera of the latter tribe.

Tetracentrosternus hoffmani Golovatch, 2013 stems from Mount Gaoligong Shan, western Yunnan, China ( Golovatch 2013). Like Tetracentrosternus subspinosus , it shows adenostyles on male femora 1, a suberect gonopod telopodite with a fringed/fimbriate/spiculate and phylloid apex, and a long, unipartite gonofemoral process.

The new species described below, despite its relative geographical proximity to Tetracentrosternus subspinosus , shows a number of characters so different that the diagnosis of the genus needs to be refined. Thus, because there are no adenostyles in femora 1 of the male of Tetracentrosternus theelorsuensis sp. n., this trait can be regarded as only species-specific not only in Tetracentrosternus , but in the entire subfamily Alogolykinae . So, following Hoffman (1963), it seems best to return Touranella (three species in Vietnam, one in Nepal) to Alogolykini , as its close similarities to Tetracentrosternus are apparent. The only meaningful differences lie in gonopod structure, the femoral portion in Touranella sometimes being a little longer, the solenomere a little thicker, suberect and rod-shaped rather than flagelliform, while the femoral process when present is considerably shorter ( Golovatch 2009a, 2009b). In our opinion, a strong, rod-shaped solenomere versus a thin, flagelliform one remains the basic difference between the tribes Alogolykini and Polydrepanini , respectively. Thereby the subfamily Alogolykinae seems to be best characterized only by the absence of a clear-cut division of the solenophore or solenophore-like structure near/around the solenomere into a membranous lamina medialis and/or a similarly membranous lamina lateralis, in Polydrepanini often coupled with a twisted, helicoid course of the seminal groove. In addition, the gonofemorite in Alogolykinae is often strongly abbreviated while many species show adenostyles on the male first femora. The latter two traits are also characteristic of the subfamily Australiosomatinae , but the solenophore branch or branches remain free and never sheath a primitively long, strong and rod-like solenomere. A more detailed review of these subfamilies and their tribes (see Jeekel 1968) lies far beyond the scope of the present note.

The gonopod telopodite in Tetracentrosternus theelorsuensis sp. n. is strongly elongate and unciform, bearing three evident processes in the distal half, whereas the solenomere is particularly long and nearly as long as the solenophore, while the femoral process is also very long, but deeply bipartite. Besides this, as in Tetracentrosternus subspinosus , the strongly abbreviated gonofemoral part in the new species is delimited distally by a distinct ridge, as opposed to a strong spine in Tetracentrosternus hoffmani .

In terms of metatergal structure, Tetracentrosternus theelorsuensis sp. n. is somewhat intermediate between both congeners, the tegument being only moderately rugulose as opposed to nearly smooth in Tetracentrosternus subspinosus or rather clearly tuberculate in the rear halves of metaterga in Tetracentrosternus hoffmani .

There is little doubt that more species of Tetracentrosternus await discovery at least in and between eastern Myanmar and southern China, including Thailand (Fig. 4). The same certainly holds true for some other Alogolykini as well, e.g. Touranella .