Sinocallipus similis, Nguyen & Stoev & Vu, 2025

Nguyen, Anh D., Stoev, Pavel & Vu, Tam T. T., 2025, Integrative data reveal a new millipede species of Sinocallipus Zhang, 1993 (Callipodida, Sinocallipodidae) from Vietnam, with notes on its phylogeny, Zoosystematics and Evolution 101 (1), pp. 69-80 : 69-80

publication ID	https://doi.org/ 10.3897/zse.101.138716
publication LSID	lsid:zoobank.org:pub:0F9E72F6-2E43-4B0B-9BAD-29F2EF728396
DOI	https://doi.org/10.5281/zenodo.14606477
persistent identifier	https://treatment.plazi.org/id/1A43DAD4-C525-5126-B9A6-4DAF10497489
treatment provided by	Zoosystematics and Evolution by Pensoft
scientific name	Sinocallipus similis
status	sp. nov.

Treatment

Sinocallipus similis sp. nov.

Figs 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 A View Figure 9 , 10 View Figure 10

Material examined.

Holotype. Vietnam • ♂; Tuyen Quang Province, Lam Binh District, Na Hang Nature Reserve, Khuoi Pin Cave ; 22.57134°N, 105.30977°E; 457 m a. s. l.; 26 June 2024; XS Le leg.; IEBR-Myr 994 H . GoogleMaps

Paratypes. Vietnam • 2 ♂♂, 1 ♀; same as for holotype; IEBR-Myr 994 P GoogleMaps • 3 ♂♂, 1 ♀; same locality as the holotype, but Na Mang Cave , 22.45405°N, 105.32204°E, 305 m a. s. l.; 25 June 2024; XS Le leg.; IEBR-Myr 990 GoogleMaps • 1 ♂, 1 ♀; same data as for IEBR-Myr 990; NMNHS GoogleMaps • 1 ♀, 2 juvs.; same data as for IEBR-Myr 990; IEBR-Myr 991 GoogleMaps .

Description of type locality.

The species was discovered in two caves within the Na Hang Nature Reserve, Tuyen Quang Province in northern Vietnam. Khuoi Pin Cave is located on the mountainside, measuring approximately 300 meters in length and 10 meters in height. The cave floor consists of sandy soil and small rocks. It is notably wet, with some water flow on the ground, and the air humidity is around 90 %, while the temperature remains consistently at 20 ° C. The cave also contains numerous small branches contributing to its unique ecosystem (Fig. 3 A, C, D View Figure 3 ).

Na Mang Cave is situated near the base of the mountain. Its floor consists of sandy soil. Similar to Khuoi Pin Cave, it exhibits high humidity levels (around 90 %) and maintains a consistent temperature of 20 ° C. The cave is small and narrow with water flows on the ground (Fig. 3 B View Figure 3 ).

Both caves are recognized for their rich biodiversity, hosting a variety of species, including several unidentified glyphiulid, haplodesmid and callipodidan millipedes, as well as spiders, crickets, and bats. Notably, all millipede specimens were gathered from the aphotic zone in both caves, indicating that the species are specialized to the cave environment.

Etymology.

From the Latin word “ similis ” meaning “ similar ” or “ like ”. The name denotes the morphological similarity between the new species and Sinocallipus deharvengi from Quang Binh Province in Vietnam.

Diagnosis.

This species can be recognized by having up to 79 pleurotergites (in adult females, males with 78), yellowish body, long antennae, 5 + 5 crests between the ozopores on midbody PTs, almost equally subdivided paraprocts, gonopods with strongly swollen and long gonocoxal process g, and a long, trochanteral process of leg 9 with a pointed tip.

Diagnosis remarks.

It can be distinguished from S. deharvengi by antennal length (9.5 mm in S. similis vs. 9.7 mm in S. deharvengi ), antennal coloration (antennomere 2 yellow, antennomeres, 3–5 partially brown in S. similis vs. antennomere 2–5 brown in S. deharvengi ), different shape of trochanteral process h (long with a pointed tip in S. similis vs. short in S. deharvengi ) and length of gonocoxal process g (2 × as long as process k in S. similis vs. 3 × as long as process k in S. deharvengi ); from S. catba by: body colouration (yellow in S. similis vs white in S. catba ), length of gonocoxal process g (2 × as long as process k in S. similis vs 1.5 × as long as process k in S. catba ), division of paraproct (paraprocts divided into two almost equal-sized sclerites in S. similis vs paraprocts divided into larger ventral and smaller dorsal sclerites in S. catba ). Pairwise genetic distances for COI between S. similis sp. nov., and S. catba and S. deharvengi are 17.1 % and 21.9 %, respectively.

Description.

Male. Body rings 65–78 PT plus telson (Holotype ♂: 71 PT plus telson). Length 68.4–72.3 mm (Holotype ♂: 70.5 mm), width of midbody PT 3.2 mm, height of midbody PT 3.4 mm.

Colouration: Body uniformly white-yellowish in alive specimens (Fig. 3 D View Figure 3 ) and yellow in preserved specimens, without particular colouration pattern, metazonites without posterior band. Head: Uniformly pale yellow, pilose; cephalic suture visible on vertex (Fig. 4 B View Figure 4 ). Antennae: Long, extending beyond the posterior edge of PT 10 when folded backwards; antennomeres, 2 yellow, 3–5 partially brown, 6–7 light yellow (Fig. 4 A View Figure 4 ); length of antennomeres, 1: 0.3 mm, 2: 2.1 mm, 3: 2.5 mm, 4: 1.6 mm, 5: 1.7 mm, 6: 0.9 mm, 7: 0.4 mm; antennomere ratio: 3> 2> 5> 4> 6> 7> 1; tip of antennomere 7 with four short cones (Fig. 4 C View Figure 4 ). Eyes: Black, well-delineated, composed of 32–34 ocelli in 4 rows (Fig. 4 D View Figure 4 ).

Trunk: Width of PT: 1 = 2 = 3 <4 <5 <6 <7. PT higher than broad, ratio: 1.06: 1. Dorsal side of collum and PT 2–3 smooth. Crests not well developed, but more obvious dorsally, 5 + 5 between the ozopores on midbody PT, anterior part of crests broad, abruptly narrowing posteriorly (Figs 5 A View Figure 5 , 6 A View Figure 6 ); 8–10 poorly developed crests under the ozopores. Ozopores small, barely visible on PT 5–6, clearly visible, lying on crest 6 in midbody PT, missing on the last 4 PT. Telson: Paraprocts divided into two, almost equal-sized dorsal and ventral sclerites; dorsal sclerite surmounted by two macrosetae situated on tiny lobes (Fig. 5 C View Figure 5 ). Spinnerets long and slender, ending with a long seta (Fig. 5 B, C View Figure 5 ). All setae on telson dark brown, contrasting with the yellow background (Fig. 5 B View Figure 5 ).

Legs: All legs yellowish, long and slender, ending with a long claw. Tarsal pads very poorly developed, present on leg pairs 3–12. No particular modifications on coxae of pregonopodal legs. Coxal sacs present on pregonopodal legs (Fig. 5 D View Figure 5 ). Prefemora of legs 4–7 normal.

Leg-pair 9 (Figs 7 A, B View Figure 7 , 9 A View Figure 9 ): Coxite roundly subtrapezoidal; trochanter expanded medio-ventrad forming a rather elongated process h with a long, pointed tip, and a tiny triangular process z.

Chaetotaxy: All setae broken off. The last two PT each with 9 + 9 setae.

Gonopods (Fig. 8 View Figure 8 ): Coxite (cx) large and broad; the large coxal process g more than 2 x the length of process k, processes g and k apically rounded, not truncated. Prefemorite condensed, short, 0.25 × as long as femorite length. Femoroid (fe) long, but stout, sparsely setose on distally antero-lateral and postero-lateral sides; distal part with three slender, acicular (n), and one shorter and subfalcate (m) terminal projections. Cannula (ca): long, slender, filiform.

Female. 75–79 PT + telson; larger than males (length: 72.5–74.8 mm. width of midbody PT: 3.8–4.0 mm; height of midbody PT: 3.8–4.0 mm, ratio: 1: 1), body color darker, lateral sides light brownish; midbody PT crests more developed than in males (Fig. 6 B View Figure 6 ); second leg-pair unmodified; cyphopods cylindrical, highly elevated (Fig. 7 C View Figure 7 ).