Orthomorpha scabra grandis Jeekel, 1964,

Likhitrakarn, Natdanai, Golovatch, Sergei I., Semenyuk, Irina, Efeykin, Boris D. & Panha, Somsak, 2019, Review of the millipede genus Orthomorpha Bollman, 1893 (Diplopoda, Polydesmida, Paradoxosomatidae) in Vietnam, with several new records and descriptions of two new species, ZooKeys 898, pp. 121-158 : 121

Orthomorpha scabra grandis Jeekel, 1964, var. nov. Figs 17 , 18

Material examined.

4 ♂ (ZMUM Rd 4268, Rd 4266, Rd 4267, Rd 4269), Vietnam, Lam Dong Province, Bidoup Nui Ba National Park, Mount Bidoup, 12°05'58"N, 108°39'30"E, 2,000 m a.s.l., mixed cloudy mossy forest on mountain top, on forest floor, night time, 16.VI.2018, I. Semenyuk leg.

Name.

Adjective to emphasize the unusually large size of the animals. Normally, no Latin names are to be applied to varieties as infrasubspecific categories, but because this new variety had first been qualified and described as a new species based on purely morphological grounds before the molecular evidence showed it to be the same as O. scabra , we allot it the previously chosen name grandis and treat it separately in our analyses, key, and map. This is also one of the direct consequences of the molecular analyses accepted in our study.

Diagnosis.

Distinguished from all known congeners or varieties by the particularly large size, coupled with the clearly tuberculate metaterga, caudolaterally rounded paraterga 1-14, and the relatively short gonopodal femorite.

Description.

Length 44-50 mm, width of midbody pro- and metazonae 3.5-3.8 and 5.2-5.6 mm wide on midbody pro- and metazonae, respectively (♂).

Colouration in alcohol after ten months of preservation dark brown ( Fig. 17 A–G ); metaterga, paraterga and epiproct red-brown to dark brown; legs, antennae and sterna light brown to light yellow; head brownish to brown.

Clypeolabral region densely setose, vertigial region sparsely so; epicranial suture distinct. Antennae rather long ( Fig. 17B ), reaching the end of body segment 3 when stretched dorsally. In width, head <segment 3 <4 <collum <segment 5 <2 <6-14, body gently and gradually tapering thereafter. Collum with three transverse rows of setae: 3+3 in anterior, 2+2 in intermediate, and 4+4 in posterior row; a slight furrow laterally in posterior 1/3; caudal corner of paraterga very broadly rounded, slightly upturned, but not drawn behind rear margin ( Fig. 17A, B ).

Tegument shining, prozonae finely shagreened, postcollum metaterga rugose to rugulose and clearly tuberculate, surface below paraterga finely microgranulate and rugulose. Postcollum metaterga each with two transverse rows of abraded setae: anterior (pre-sulcus) row with 2(3)+2(3) mostly minute tubercles, short wrinkles or traceable only as insertion points, posterior (postsulcus) row with 3 –5+3– 5 setae borne on low, oblong, rounded tubercles or minute knobs. Tergal setae long, slender, ca. 1/3 of metatergal length. Axial line rather clear, especially so on metazonae.

Paraterga 2 broad, anterior edge evidently convex, lateral edge with three minute incisions in anterior 1/4 to half; posterior edge oblique ( Fig. 17A ). Anterior edges of following paraterga regularly rounded, lateral edge without incisions, posterior edge oblique to regularly concave, especially strongly concave in segments 14-19 ( Fig. 17 E–G ). Calluses on paraterga 2-4 strongly delimited by a sulcus only dorsally, on following paraterga both dorsally and ventrally.

Following paraterga very strongly developed ( Fig. 17 A–F ), upturned, lying below dorsum until segment 4, following ones above dorsum, caudal corner ranging from obtuse-angular to subrectangular, always and increasingly extending behind rear tergal margin ( Fig. 17 A–C ), from segment 15 on spiniform, long and pointed; in lateral view, paraterga thinner in poreless segments and modestly enlarged in pore-bearing ones.

Ozopores evident, lateral, lying inside an ovoid groove at ca. 1/4 in front of caudal corner. Transverse sulcus usually distinct ( Fig. 17A, C, F ), complete on metaterga 5-18, incomplete on segment 4, wave-shaped, rather shallow, nearly reaching the bases of paraterga, very faintly ribbed at bottom. Stricture between pro- and metazona rather wide and deep, very faintly ribbed at bottom down to base of paraterga ( Fig. 17A, C, F ). Pleurosternal carinae complete crests with a sharp caudal tooth on segments 2-4(8), thereafter bulged anteriorly and with a small, sharp, caudal tooth on segments 8-13, the tooth gradually reduced into small, caudally roughly granulate crests until segment 16 ( Fig. 17B, D, E ). Epiproct ( Fig. 17F, G ) conical, flattened dorsoventrally, with two evident apical papillae; tip subtruncate; pre-apical papillae very small, but traceable, lying rather close to tip. Hypoproct subtriangular, setiferous knobs at caudal edge evident and well-separated.

Sterna sparsely setose, without modifications except for two rather large and long, fully separated, sternal cones between ♂ coxae 4 ( Fig. 17H, I ). A paramedian pair of small tubercles in front of gonopod aperture. Legs long and slender, midbody ones ca. 1.3-1.4 times as long as body height, prefemora without modifications, ♂ tarsal brushes present until legs 7.

Gonopods ( Fig. 18 ) simple. Coxa slender and long, with several setae distoventrally. Femorite relatively short, ca. 2 times as long as prefemoral (= strongly setose) part. Femorite slender, moderately curved, “postfemoral” portion demarcated by an oblique lateral sulcus; solenophore with a tridentate tip, middle denticle shorter than terminal tooth, but longer than a small subterminal lobule; solenomere long, flagelliform, tip barely exposed.

Remark.

This species was found only on Mount Bidoup in the summit area, while none of the inspected adjacent forests, even those located at the same altitudes, including a very similar forest on Mount Hon Giao, failed to reveal these millipedes. On Mount Bidoup, this species was quite abundant, occurring mainly on the forest floor, on logs and at bases of tree trunks in the night time, as well as under logs in the daytime.

Figures

Figure 17. Orthomorpha scabra Jeekel, 1964, grandis var. nov., ♂ A habitus and live colouration B, C anterior part of body, dorsal and lateral views, respectively D, E segments 10 and 11, dorsal and lateral views, respectively F-H posterior part of body, dorsal, ventral and lateral views, respectively I, J sternal cones between coxae 4, subcaudal and sublateral views, respectively.

Figure 18. Orthomorpha scabra Jeekel, 1964, grandis var. nov., ♂, left gonopod A, B mesal and lateral views, respectively. Scale bar: 0.5 mm.