Gnomognathus dhoni, Sudhakaran & Kuruvila, 2025

Sudhakaran, Nikhila & Kuruvila, Manju Elizabeth, 2025, A new millipede species of the genus Gnomognathus Attems, 1942 (Diplopoda, Spirostreptida, Harpagophoridae) from South India, Zootaxa 5659 (3), pp. 335-356 : 337-342

Gnomognathus dhoni sp. nov.

Figs 1A , 2 , 3 , 4

Type material. Holotype: Male ( ZSIK Reg. No. ZSI/ WGRC /I. R.-INV.28938), Dhoni (10°51.956’N, 76°37.223’E), approximately 15 km away from Palakkad town , Palakkad District, Kerala State, India, 140 m a.s.l., near stream close to the teak plantations hidden inside soil, 30 August 2024, hand-collected by Nikhila Sudhakaran . Paratypes: 3 males, 3 females (RDZ-ACP-SS201), and 1 female ( ZSIK Reg. No. ZSI/ WGRC /I. R.-INV.28499), same locality, hand-collected from leaf debris .

Etymology. The species epithet dhoni , a noun in apposition, refers to the type locality of the species: the Dhoni Reserve Forest in Palakkad District of Kerala, India.

Diagnosis. The anterior coxal fold (AC) of G. dhoni sp. nov. ( Figs 2A , 4A ) is most similar to G. nanus ( Carl, 1941) ( Fig. 9A ) in overall shape but differs from it mainly by the semicircular transverse ridge (tr) on AC surface and the indentation followed by the baso-lateral process (blpAC) on lateral margin, both of which are absent in G. nanus . Structure of the telopodite ( Figs 3 , 4D, E ) of G. dhoni sp. nov. is closely similar to congeners in the tricolor group ( G. tricolor , G. eremitus , and G. vicarius ) ( Fig. 10A–C ) in that the telopodite terminates in the palette with xyrochaetae (xc) and serrated border (sb) on either side, and a smaller marginal lobe (ml) is present basal to the palette, but differs from them specifically by the shape and position of the two tibial spines on the telopodite: a short tibial spine 1 (ts1) and a long tibial spine 2 (ts2), placed on the outer surface of the telopodite. Telopodite of G. dhoni sp. nov. is also similar to G. helicogonus ( Carl, 1941) ( Fig. 10D ) but differs by being non-spiraled and having a femoral spine (fs); the apical part with a serrated border (sb) on the palette and a marginal lobe (ml). In G. helicogonus , telopodite is spirally twisted, without a femoral spine; the apical part is without additional lobes but bears additional spines along with xyrochaetae.

G. dhoni sp. nov. differs from G. minusculus , G. interfectus , and G. macracanthus ( Fig. 9B, D, E ) mainly by its wider anterior coxal fold (AC) and varied structure of the mesal process (mp) and antero-lateral process (alp). It further differs from them by the presence of the indentation and baso-lateral process (blpAC) and a transverse ridge (tr) on the anterior coxal fold; both absent in these three species. Apical part of the telopodite of G. dhoni sp. nov. being similar to that of the tricolor group lacks any additional spines and is unbranched, with lobes of unequal size. In G. minusculus apical part is branched, as it is in G. interfectus and G. macracanthus , with additional spines and lobes of almost equal size in latter two (apical part not lobed or branched in G. macracanthus Form A) (further comparison in Table 1).

Description. Color . Live specimens mostly brown ( Fig. 1A ). In alcohol, prozonites grey. Anterior metazonites brownish black, and posterior metazonites orange red with a thin golden posterior margin. A diffused orange red spot runs across the dorsal side up to the epiproct. Anterior end of the specimens comparatively darker. Ventral side, near to legs, orange-red.

Body. Males with 58 podous rings and telson, length ca. 59 mm, width ca. 2.5–3 mm. Females with 58–60 podous rings and telson, length ca. 55–61 mm, width ca. 3–3.5 mm. Head smooth. Ommatidia ca. 35–36, arranged in five rows. Females with ommatidia ca. 30–31 arranged in 5–6 rows. Head smooth and shiny. Interocular groove shallow; barely visible in female. Labrum teeth: 3; 6–8 labral setae. Five setiferous foveolae; 4–5 in females. Circular antennal cavity. Antennae laterally compressed, reaching the middle of second body ring. Female antennae shorter and laterally compressed, almost reaching the posterior edge of collum.

Gnathochilarium normal type. Mentum smooth. Stipites with single seta placed on distal bump, proximally with a line of 5–6 setae adjacent to mentum; female stipites without distal bump, only setae present. Lamellae linguales with two distal setae, one middle seta, and proximally with 2–3 on the left and six setae on the right lamella linguales repectively. Mandibular stipites proximally rounded, laterally flat, and distally drawn inward into a hook; in females not hooked, distally with two obscure tips.

Collum laterally sub-rectangular, antero-lateral edges thickened; female antero-lateral corner more rounded.

Anterior prozonites with fine transverse striations reaching up to the ventral sides; posterior prozonites smooth; transverse suture visible between them. Metazonites with deep longitudinal striations on lateral and ventral sides; striations not surpassing the ozopores. Ozopores situated laterally in the center of metazonites. Sternites with five transverse striations, last three more prominent, groove-like.

Legs. Prefemur of first pair of legs extended outward into a rounded lobe. From the second pair, legs padded on postfemur and tibia; padding weak and incomplete, limited to lining the lateral margins. Femur of walking legs with a longitudinal depression on ventral side. Female legs without pads or longitudinal depression. Anal valves rough with well-developed lips; valves wider in males than in females. Preanal process short, blunt, and not extending beyond the anal valves; shorter in females. Anal scale small, straight.

Gonopods. Anterior coxal fold (AC) basally slender and rounded, expanding towards the apex after a constriction, distally wide, laterally weakly curved backward ( Figs 2A , 4A ). Distal margin with three processes: mesal process (mp) well developed, curved inward, beaked, and spiny at the end; paramedian process (pp) reduced, only a minute and inconspicuous protuberance on distal margin; antero-lateral process (alp) rounded and extending backward, pointed in anterior view. A semicircular transverse ridge (tr) originates between the latter two processes. Below the ridge, a channel formed, extending up to the tip of alp ( Figs 2A , 4A ). Lateral margin of AC with strong indentation followed by a prominent, thick, rectangular baso-lateral process (blpAC) with rounded corners extending backward, lying adjacent to and intersecting with baso-lateral process (blpPC) of posterior coxal fold ( Figs 2B, C , 4C ). Posterior coxal fold (PC) with a rounded postero-lateral process (plp) and a conical blpPC bending inward, with a groove inside ( Figs 2C , 4C ). plp keeps the femoral spine from extending mesad, and blpPC clasps the telopodite in place. Telopodite base with single twist ( Fig. 3A ). Single femoral spine (fs) pointed and S-shaped. Free part of the telopodite bending and projected laterad, forming an incomplete circle ( Figs 2B , 4B ); with two tibial spines. Tibial spine 1 (ts1) short, curved, and pointed, positioned near outer edge; tibial spine 2 (ts2) long, straight, and pointed, located centrally on outer surface above ts1 ( Figs 3B , 4E ). Seminal groove (sg) on outer surface of telopodite, ending on palette. Apical part of the telopodite terminates in the palette. One side of palette with a row of nine xyrochaetae (xc) arranged close to the seminal groove (sg); other side thinner, translucent with an apical serrated border (sb). Base of palette with small, rounded marginal lobe (ml) folded inward ( Figs 3 , 4D, E ).

Note. blpAC slightly bilobed in one male. A male with a broken femoral spine was also found. Xyrochaetae varies in number, as some seem to be broken off.

Figures

FIGURE 1. A. Gnomognathus dhoni sp. nov. B. Dhoni Forest, Palakkad, Kerala. Photos by Ms. Chinchu Devasia.

FIGURE 2. Gnomognathus dhoni sp. nov., gonopods (paratype males, RDZ-ACP-SS201). A. Left gonopod without telopodite, anterior view. B. Right gonopod with telopodite, posterior view. C. Left gonopod without telopodite, posterior view. D. Right gonopod without telopodite, mesal view. Scale bars = 0.3 mm.

FIGURE 3. Gnomognathus dhoni sp. nov., telopodite (paratype males, RDZ-ACP-SS201). A. Right telopodite with broken femoral spine, posterior view. B. Left telopodite with broken base, anterior view. C. Apical part of telopodite, inner side. D. Apical palette, outer surface. Scale bars: A, B = 0.2 mm; C = not to scale; D = 0.4 mm.

FIGURE 4. Gnomognathus dhoni sp. nov., gonopods (paratype male, RDZ-ACP-SS201).A. Gonopods with telopodite, anterior view. B. Gonopods with telopodite, posterior view. C. Left gonopod without telopodite, posterior view. D. Left telopodite, posterior view. E. Left telopodite, anterior view. Abbreviations. AC: anterior coxal fold; alp: antero-lateral process; blpAC: baso-lateral process of anterior coxal fold; blpPC: baso-lateral process of posterior coxal fold; fs: femoral spine; ml: marginal lobe; mp: mesal process; pp: paramedian process; PC: posterior coxal fold;; plp: postero-lateral process; px: paracoxite; sb: serrated border; sg: seminal groove; tr: transverse ridge; ts1: tibial spine 1; ts2: tibial spine 2; xc: xyrochaetae. Scale bars = 1 mm.

FIGURE 9. Gonopods of previously described Gnomognathus species. A. G. nanus (Carl, 1941). B. G. minusculus (Attems, 1936). C. G. macracanthus (Carl, 1941) (Form B). D. G. interfectus (Carl, 1941). E. G. macracanthus (Carl, 1941) (Form A) (Figures reproduced from Attems (1942) and Carl (1941)).

FIGURE 10. Gonopods of previously described Gnomognathus species. A. G. tricolor (Carl, 1941). B. G. vicarius (Carl, 1941). C. G. eremitus (Carl, 1941). D. G. helicogonus (Carl, 1941) (Figures reproduced from Carl (1941)).