Polydrepanum fissum Sankaran & Sebastian 2018, sp. nov.
Creators: name: Sankaran, Pradeep M.
name: Sebastian, Pothalil A.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Diplopoda
Polydesmida
Paradoxosomatidae
Polydrepanum
Polydrepanum fissum

description: Polydrepanum fissum sp. nov.
(Figs 1–4, 7)
Type material: Holotype: Male (MILLI-ADSH0005), INDIA: Tamil Nadu: Salem, Yercaud, near the foothills of Kiliyur Falls, 11o47'45.1''N, 78o12'02.6''E, 1167 m alt., 3 December 2017, M. S. Pradeep leg., from litter, by hand. Paratypes: 2 males (MILLI-ADSH0006), same data as holotype.
Etymology. The specific epithet refers to the bifurcated solenophore tip of the new species (Fig. 4A, 1 st and 2nd arrows). Latin fissum = split, neuter.
Diagnosis. Polydrepanum fissum sp. nov. seems to be especially similar to P. tamilum, at least concerning the complexity of the gonopods, but can be distinguished from the latter by the following combination of characters: femorite with a lateral thumb-like process and paired apical folds (femorite of P. tamilum lacks such modifications), solenophore with a moderately and regularly curved distal part (solenophore of P. tamilum with a strongly curved/coiled distal part) and solenophore without mesal process (solenophore of P. tamilum with paired mesal processes) (compare Figs 3E–F, 4A–C with Carl 1932: figs 17–18). The occurrence of paired apical demarcation sulci/folds of gonopodal femorite relates P. fissum sp. nov. with the Polydrepanum sp. 1 illustrated by Bano and Murthy (1997). However the complexity of tibiotarsus of the former clearly distinguishes it from the latter (compare Fig. 4A–B with Bano & Murthy 1997: fig. 10A–B and herein Fig. 6D).
Description. Male. Body with 20 segments. Length ca 15 mm, width of midbody pro- and metazonites 1.1 and 1.2 mm, respectively. Width of midbody paranota 0.1 mm. Colouration of live animals uniformly chocolate brown; antennae, postero-lateral part of paranota and surface below paranota all chocolate brown; legs and sternites coffee brown. Colouration of alcohol material after preservation faded to brownish, postero-lateral part of paranota pale brown, sternites and legs straw coloured.
Head slightly wider than collum with paranota (1.4/ 1.3 mm) in dorsal view (Fig. 2C); relative ring widths: collum ± 1 ~ 2 <3 <(4 = 16)> 17> 18> 19. Vertex shiny, sparsely setose; frons, stipes, cardo, clypeus moderately setose; epicranial sulcus distinct, ending at midanterior level of antennal sockets. Antennae moderately long (3.0 mm), filiform, reaching dorsally until waist of ring 4; relative antennomere lengths: 2 <3> 4 <5> 6; antennomere 6 widest apically; post-antennal groove shallow; antennal socket diameter and isthmus between them 0.2 and 0.3 mm, respectively.
Collum with lateral margin weakly produced as a paranotum (Fig. 2E), anterior, lateral and posterior margins slightly concave, without any posterior marginal setae (Fig. 2C); collum dorsally bearing four transverse rows of white, short, fragile setae of nearly parallel rows.
Anterior and posterior margins of segments almost straight, with posterior marginal setae (Fig. 2D, F–G).
Paranota of segments set high, lying parallel to axial line and below dorsum (Fig. 2E, H), posterior corner of collum paranota and paranota of haplosegments 1–2 regularly rounded (Fig. 2C–D), that of paranota of haplosegment 3 and diplosegments until 12th produced posteriorly as broad triangles (Fig. 2D, F–G), that of diplosegments 13–19 strongly produced posteriorly as acute triangles (Fig. 2L), posterior corner of paranota of haplo- and diplosegments widely spaced from each other (Fig. 2E, H); anterior margin of paranota of collum, haplosegments 2–3 and diplosegments until 17th nearly regularly rounded, that of diplosegments 18–19 shallow (Fig. 2D, F–G, L); paranota on haplosegment 1 larger than paranota of haplosegments 2–3 (Fig. 2D), slightly lower than lateral margins of collum and preceding paranota (Fig. 2E), lying close to that of collum, but away from that of haplosegment 2 (Fig. 2E); lateral margins of paranota of haplosegments and diplosegments until 17th with paired weak marginal incisions, one anterior incision, one median (Fig. 2D, F–G); lateral margins of paranota thicker on pore-bearing rings (Fig. 2H).
Pleural keels well marked on haplosegments as triangular bulging, that on diplosegments less evident as narrow thickenings.
Prozonites smooth. Metazonites, surface below paranota granulate; metazonites with moderate pubescence (Fig. 2M); transverse sulcus on metazonites distinct from diplosegments 1–18, reaching paranotal base (Fig. 2F– G); limbus a thin, continuous ribbon. Axial line clearly traceable both on pro- and metazonites until diplosegment 18th (Fig. 2C–D, F–G).
Pore formula normal (5, 7, 9, 10, 12, 13, 15–19); ozopore small, circular, opening posterolaterally on thickened paranotal margin, away from the level of transverse sulcus of metazonites (Fig. 2H).
Sterna moderately setose, as wide as long, transverse impressions more distinct than longitudinal ones, without modifications except for a single chisel-shaped, setose lamella between coxae 4 (Fig. 2N).
Legs slender, with well developed tarsal brushes (Fig. 3A–D), with short claws; all coxae and prefemora bearing a single, ventral, stiff, long seta; relative podomere lengths: femur> tarsus> postfemur> (prefemur ~ tibia); all prefemora swollen laterally; leg pair I possesses small, rounded, midway, ventral tubercle/adentostyle (Fig. 3A, left inset) on femur; femora on leg pair II ventrobasally with a prominent conical tubercle/ adenostyle (Fig. 3B).
Gonopore small, round, opening on short, anterolateral mound-like bulging on coxae 2 (Fig. 2O).
Pre-anal ring sparsely setose; epiproct conical, flattened dorsoventrally, extending beyond anal valves, tip truncate (Fig. 2K, M); hypoproct triangular (Fig. 2L).
Gonopods (Figs 3E–F, 4A–C). Gonopod aperture transversely oriented, roughly triangular in outline, about 2/3 as wide as prozonite 7, with a well marked, raised lateral rim, anterior and posterior rims with median projections (Fig. 2P). Gonopods high, complex, lying close to sternites. Coxite about as long as femorite, subcylindrical, distally broadened, setose distodorsally (Figs 3F, 4B). Cannula as usual (Fig. 4B). Prefemur short, globose, as usual densely setose (Figs 3E–F, 4A–B), with a moderately long and stiff seta distoventrally (Fig. 4B, 4 th arrow), with a distal sulcus evidently demarcating acropodite (Fig. 4A–B). Femorite long, subcylindrical, with incomplete torsion limited to basal 1/4th part (Figs 3E–F, 4A–B), distolaterally with a thumb-like process (Fig. 4C). Seminal groove running along dorsal side of femorite, turning laterally near apical folds on femorite, then turning mesally before entering onto solenomere, strongly curved distally (Fig. 4A). Postfemoral part clearly set off from femorite by two oblique demarcation sulci/folds (Fig. 4A–B). Solenophore short, evidently branched, only with lamina lateralis (Fig. 4A), distally curved as a sickle (Figs 3E, 4A), with bifurcated tip, lateral branch slightly longer than mesal, both directed laterally (Fig. 4A, 1 st and 2nd arrows), basomesally with two membranous, triangular, wing-like processes, 1 st large, 2nd small (Fig. 4B), with a widely triangular process (Fig. 4B), basolaterally with a flat, lamellate process (Fig. 4C); lamina lateralis well developed, with a short disolateral process (Fig. 4C), with mesal triangular process (Fig. 4A), distal 2/3rd folded to juxtapose with the ventral face of solenophore, proximal 1/3rd wide, lying slightly away from solenophore (Fig. 4A). Solenomere simple, slender, median part enclosed within lamina lateralis, with moderately exposed, angular tip (Fig. 4A, 3 rd arrow).
Female. Unknown.
Note. Polydrepanum fissum sp. nov. is quite distinct from other known Polydrepanum spp. as its leg pair I possesses adenostyle and gonopodal femorite poorly torsate, which all warrant the erection of a new genus for it. However, a distally sickle-shaped solenophore with only lamina lateralis, a flagelliform solenomere enclosed by the lamina lateralis and the seminal groove, which run along the dorsal face of the femorite fit this species into Polydrepanum. The occurrence of adenostyle on leg pair I and gonopodal femorite with less evidence of torsion of P. fissum sp. nov. suggests that it may be a derived clade within Polydrepanum, but confirmation requires phylogenetic treatment.
Distribution. Only known from the type locality (Fig. 7).
description: Published as part of Sankaran, Pradeep M. & Sebastian, Pothalil A., 2018, A new species of and a new transfer from the millipede genus Polydrepanum Carl, 1932 (Polydesmida, Paradoxosomatidae, Polydrepanini), pp. 169-178 in Zootaxa 4471 (1) on pages 170-175, DOI: 10.11646/zootaxa.4471.1.8, http://zenodo.org/record/1439580