Zephronia enghoffi, Srisonchai & Sutcharit & Likhitrakarn, 2021

Srisonchai, Ruttapon, Sutcharit, Chirasak & Likhitrakarn, Natdanai, 2021, The giant pill-millipede genus Zephronia Gray, 1832 from Thailand, with a redescription of Z. siamensis Hirst, 1907 and descriptions of three new species (Diplopoda, Sphaerotheriida, Zephroniidae), ZooKeys 1067, pp. 19-56 : 19

Zephronia enghoffi sp. nov.

Figures 2A, B ; 7 ; 8 ; 13C, D ; 14B

Type material.

Holotype: Thailand - Khon Kaen Province • ♂; Tham Phaya Nakharat; 16°48'52"N, 101°57'16"E; 528 m a.s.l.; 21 July 2020; R. Srisonchai, C. Sutcharit leg.; CUMZ-Zeph0005. Paratypes: Thailand - Khon Kaen Province • 4 ♂♂ 3 ♀♀; same locality as holotype; CUMZ-Zeph0006 • 2 ♀♀; same Province, Chum Pae District, Tham Poo Lup; 16°49'45.4"N, 101°59'7.6"E; 346 m a.s.l.; 10 October 2014; R. Srisonchai, C. Sutcharit leg.; CUMZ-Zeph0006. Further specimens, not paratypes: Thailand - Loei Province • 1 ♂ 2 ♀♀; Wang Saphung District, Pak Puan Arboretum; 17°21'20"N, 101°44'59"E; 316 m a.s.l.; 10 October 2014; R. Srisonchai, C. Sutcharit leg.; CUMZ-Zeph0006.

Etymology.

This species is named after Henrik Enghoff from Natural History Museum of Denmark, University of Copenhagen, Denmark, the Danish myriapodologist who initiated an important research step on millipede studies for Thailand.

Diagnosis.

A member of Zephronia s. s. in which the position of Tömösváry’s organ located next to the aberrant ommatidia, not inside the antennal groove. Adult body length medium,> 29 mm, usually ca. 32 mm, up to 36 mm; body brown or dark brown, inner surface (underside) of anal shield with a single locking carina on each side, and leg-pair 2 of male coxa with a long membranous lobe at mesal margin. Similar in these respects to Z. golovatchi sp. nov., but differs from this species by the following combination of characters; antenna short, leg-pair 2 of female coxa apico-mesally with large and conspicuous coxal ridge, operculum of vulva regularly rounded and narrow in posterior view, mesal margin of operculum tapering apically, central margin (tip) of subanal plate shallowly concave, process of telopoditomere 2 of anterior telopod quite long and equal in length to the combination of telopoditomeres 3+4, and immovable finger telopoditomere 2 of posterior telopod (process of telopoditomere 2) equal in length to movable finger (consisting of telopoditomeres 3 and 4).

Description.

Body length: Length in male 29.0-33.0 mm (holotype 31.0 mm), female 30.0-36.0 mm; head 4.5-5.5 mm; thoracic shield 5.5-7.0 mm; anal shield 11.0-11.5 mm.

Body width: Width in male 16.0-18.5 mm (holotype 18.0 mm), female 16.0-19.0 mm; head 9.0-10.0 mm; thoracic shield 16.0-18.0 mm; anal shield 14.0-17.0 mm.

Body height: Height in male 10.0-12.0 mm (holotype 11.0 mm), female 10.0-13.0 mm; thoracic shield 10.0-12.0 mm; tergite 10.0-13.0 mm.

Color (Fig. 2A, B ): Specimens in life with light brown to brown color; antennae dark brown; head, thoracic shield, tergites, paratergites and basal part of legs brown; posterior margin of tergites dark brown; a few apical podomeres greenish brown. Color in alcohol after 8 months not changed.

Head: Wide and stout, subtrapeziform; anterior part of head with dense and long setae; central part of head glabrous; posterior part of head with dense and short setae. Labrum with a single tooth at anterior margin. Each eye with 90-100 ommatidia. Aberrant ocellus located near antennal groove (at upper part of groove).

Antenna (Fig. 7A ): Short and stout, with rounded joints; length 3.5-4 mm; reaching backward to tarsus of legs 2 or 3. Lengths of antennomeres 6> 5> 4 = 3 = 2 = 1. Antennomere 6 densely setose, sensilla basiconica surrounding apical disc. Last antennomere thickened and flattened, strongly widened apically, axe-shaped. Shape of antennae sexually dimorphic; thickened, widened apically and slightly flattened in male, in female cylindrical. Apical disc with ca. 75 apical cones. No sclerotized ridge between antennal socket and ommatidia.

Tömösváry’s organ: Separated from ommatidium, located on a brim between ommatidia and antennal socket, smaller in diameter than an individual ommatidium.

Gnathochilarium: Ventral surface with setae, other structures typical of the order. Mandibles not dissected.

Stigmatic plates (Fig. 7C ): First stigmatic plate subtriangular; apex rounded, broad, expanded apically then becoming a fanlike; curved towards coxa 1.

Laterotergites : Laterotergite 1 narrow, projecting into a sharp tip. Laterotergite 2 larger than laterotergite 1, tip weakly extended, with a round projection.

Collum: Surface glabrous, except for anterior margins near rim with isolated and long setae.

Thoracic shield: Surface as those of tergites, covered with small setae, each seta located in a tiny pit; shallow groove wide anterolaterally, with very long setae.

Tergites (Fig. 2A, B ): Quite shiny; surface densely setose, visible in normal vision; entirely covered by short setae, each locating in tiny pits; tip of paratergite of midbody tergites curved, directed posteroventrad.

Endotergum (Figs 13C, D , 14B ): Posterior margin flat, regular. Inner section (inner area) with setiferous tubercles or setae. Middle section (middle area) with a single row of elliptical cuticular impressions, distance between impressions longer than individual diameter. Bristles arranged in two rows, tip of the longest bristles extended beyond posterior margin or reaching to posterior margin.

Anal shield: Sexually dimorphic, in female very large and strongly rounded, in male slightly more rectangular. Outer surface covered by tiny and dense setae locating in small pits, similar to those of tergites. Inner surface (underside) covered by long setae; with a single, black, and long locking carina, half as long as length of last laterotergite.

Legs (Fig. 7B ): Leg-pairs 1 and 2 without apical spine. Leg-pairs 1 with 2 ventral spines, leg-pair 2 with four ventral spines. Leg-pair 3 with 5-7 ventral spines and one apical spine. Leg-pair 4 with 8-11 ventral spines, and one or two apical spines. Leg-pairs 5-19 with 8-10 ventral spines and 1-3 apical spines. Last two leg-pairs with 7-10 ventral spines and one or two apical spines. In leg 9, femur ca. 1.5 ×, tarsus ca. 2.3 × longer than wide. Length of tarsus ≥ femur> prefemur> coxa> tibia ≥ postfemur. All podomeres densely setose. Coxa large, with dentate ridge marginally (coxal process). Coxal process absent in leg-pairs 1 and 2 (except for female leg-pair 2). Leg-pair 2 of female coxa apico-mesally with large, conspicuous coxal ridge, directed laterad. Leg-pair 2 of male coxa with membranous lobe at mesal margin; lobe large and long, projecting ventrad. Prefemur without teeth. Femur rather short and stout, slightly extended mesally, mesal margin with 5-7 small teeth.

Subanal plate (Fig. 7F ): Subsemicircular, undivided, wide; central margin (tip) shallowly concave, broad; lateral margin slightly convex. Densely setose.

Male sexual characters (Fig. 7D ): Gonopore quite large, covered with a single, undivided, subsemicircular, sclerotized plate.

Anterior telopods (Fig. 8A, B, D ): Telopodite with four telopoditomeres; all telopoditomeres sparsely setose, except for the apical part of telopoditomere 3 and all parts of telopoditomere 4 without setae. First telopoditomere rectangular, slightly large and stout, broader than telopoditomeres 2-4. Telopoditomere 2 large. Process of telopoditomere 2 equal in length to the combination of telopoditomeres 3 and 4; visible in posterior view; curved and slender, 1.5X longer than wide, twice as long as telopoditomere 4; tip bent and round, directed anteriad, close to the basal part of telopoditomere 4. Margin towards telopoditomere 3 with a membranous area carrying a sclerotized process (sp), conspicuous, short, apically with sharp tip. Telopoditomere 3 with six small crenulated teeth (cr-T) in ventral side. Telopoditomere 4 short and stout, conspicuous, straight; tip round, directed mesad; with two prominent sclerotized spines in posterior side.

Posterior telopods (Fig. 8A, C, D ): Telopodite with four telopoditomeres; telopoditomeres 1 and 2 on both sides covered with sparse setae, except for immovable finger part; telopoditomere 3 at base of both inner margin and outer margin with a few setae; telopoditomere 4 without setae. First telopoditomere stout and broad, half as long as telopoditomere 2. Telopoditomere 2 slender, immovable finger (process of telopoditomere 2) as long as movable finger (consisting of telopoditomeres 3 and 4). Immovable finger long and slender, wide, 2.5 × as long as wide, not curved, tip directed mesad; at margin with several semi-circular rows of sclerotized spots. Margin towards movable finger with two conspicuous membranous lobes, triangular, inner lobe bigger and longer than outer one. Telopoditomere 3 slender, quite long, slightly expanded distad, slightly curved, thrice as long as telopoditomere 4; with a long and sclerotized spine located on a large, swollen, membranous lobe; posterior part with a row of 17-19 crenulated teeth (cr-T). Telopoditomere 4 short and stout, 1.5 × longer than wide; at inner margin with a large, conspicuous, swollen, membranous lobe and two evident sclerotized spines.

Female sexual characters (Fig. 7E ): Vulva large, covering ca. 2/3 coxa, located at mesal side, extending mesally to basal third of prefemur. Operculum regularly rounded, narrow in posterior view; mesal margin not protruding.

Distribution and habitats

(Figs 15B, C , 16 ). All specimens were collected from limestone habitats (in dry dipterocarp forest). Known only from three sites in limestone mountain ranges of Khon Kaen and Loei provinces.

Remarks. With regard to the morphological characters of coxae 2 in both male and female, this species exhibits the remarkable shape in which the male has a very long membranous lobe (Fig. 7D ) and the female displays conspicuous coxal ridges apico-mesally (Fig. 7E ). Moreover, the surface of tergites covered with conspicuous setae/hairy in Z. enghoffi sp. nov. is more distinctive than in the other two new species (Fig. 2A, B ).

Figures

Figure 2. Photographs of living Zephronia spp. A, B Zephronia enghoffi sp. nov., paratypes (CUMZ-Zeph 0006) C, D Zephronia golovatchi sp. nov., paratypes (CUMZ-Zeph 0008) E, F Zephronia panhai sp. nov., paratypes (CUMZ-Zeph 0010). Photographs not to scale.

Figure 7. Zephronia enghoffi sp. nov. A-D male holotype (CUMZ-Zeph 0005) E, F female paratypes (CUMZ-Zeph 0006) A right antenna, ventral view B the ninth left leg, posterior view C First coxae with stigmatic plates, posterior view D coxae of second legs with gonopores, posterior view E coxae and prefemur of second legs with vulvae, posterior view F subanal plate, ventral view. Abbreviations: cx = coxa, o = operculum, pre = prefemur, syn-cx = syncoxite, st-pl = stigmatic plate.

Figure 8. Zephronia enghoffi sp. nov., male holotype (CUMZ-Zeph 0005) A telopods, anterior view B anterior telopod, anterior view C posterior telopod, posterior view D right anterior and posterior telopods, ventral view. Abbreviations: cr-T = crenuations / teeth, cx = coxa, ML = membranous lobe, sp = sclerotized process, syn-cx = syncoxite.

Figure 13. SEM of endoterga of body ring 7, all from ventral views A, B Zephronia siamensis Hirst, 1907 C, D Zephronia enghoffi sp. nov. E, F Zephronia golovatchi sp. nov. G, H Zephronia panhai sp. nov. Abbreviations: cp = cuticular impression, ms = middle section, is = inner section, os = outer section, pm = posterior margin.

Figure 14. SEM of endoterga in body ring 7, all from ventral views A Zephronia siamensis Hirst, 1907 B Zephronia enghoffi sp. nov. C Zephronia golovatchi sp. nov. D Zephronia panhai sp. nov. E inner area of endotergum in Zephronia panhai sp. nov.

Figure 15. Limestone habitats of some Zephronia spp. A type locality of Zephronia siamensis (Koh Srichang, Chonburi Province) B, C type locality of Zephronia enghoffi sp. nov. (Tham Phaya Nakharat, Khon Kaen Province) D Habitat of Zephronia phrain at Phawor shrine, Tak Province.

Figure 16. Known distribution of Zephronia spp. in Thailand. Red triangle = Zephronia lannaensis; green circle = Zephronia phrain; blue triangle = Zephronia enghoffi sp. nov.; sky blue square = Zephronia golovatchi sp. nov.; purple circle = Zephronia panhai sp. nov.; yellow diamond = Zephronia siamensis Hirst, 1907; orange square = Zephronia viridisoma.