Mecistocephalus huangi Jiang & You, 2024

Pan, Yang-Yang, Fan, Jia-Bo, You, Chun-Xue & Jiang, Chao, 2024, Identification of two new species of Mecistocephalus (Chilopoda, Geophilomorpha, Mecistocephalidae) from southern China and the re-description of Mecistocephalus smithii Pocock, 1895, ZooKeys 1218, pp. 1-23 : 1-23

Mecistocephalus huangi Jiang & You sp. nov.

Figs 5 , 6

Material examined.

Holotype. • ♂; ( CMMI 20201022122 ); China, Yunnan Province, Honghe Hani and Yi Autonomous Prefecture, Jianshui County, Yanzidong Scenic Area ; 23.6359 ° N, 103.0537 ° E; 1260 m a. s. l.; 22 Oct. 2021; coll. Chao Jiang & Zhidong Wang . Paratypes. • 2 ♂♂, 4 ♀♀; ( CMMI 20201022119 , - 121, - 123, - 125, - 126, - 137); same data as holotype; 22 Oct, 2021 . • 3 ♂♂, 4 ♀♀; ( CMMI 20190122001 D- 007 D); Yunnan Province, Gejiu, Baohua Park ; 23.3545 ° N, 103.1621 ° E; 1770 m a. s. l.; 22 Jan. 2019; coll. Huiqin Ma ; • 2 ♂♂; ( CMMI 20230705004 D, 20230705005 D); same location but collected at 5 Jul. 2023; coll. Yangyang Pan & Jiabo Fan . • 1 ♂, 8 ♀♀; ( CMMI 20230830001 D- 20230830009 D); same location but collected at 30 Aug. 2023; coll. Tianyun Chen & Jiabo Fan .

Diagnosis.

A Mecistocephalus species with 49 leg pairs. Head length-to-width ratio 2, each side of clypeus with two or three smooth insulae, clypeal ratio (areolate part / non-areolate part) ~ 1, plagulae without sensilla, posterior 1 / 2 of cephalic pleurite bearing a group of setae, mandible with ~ 6 well-developed lamellae and first lamella with ~ 6 teeth. Sternal sulcus furcated at an obtuse angle. Metasternite trapezoid and with a pillow-like protrusion.

Holotype description.

Body length 69 mm; the posterior part slightly slender; head and forcipular segment dark brown in color; remainder yellow.

Cephalic plate (Fig. 5 A – C ): sub-rectangular, length-to-width ratio 2; lateral margins slightly convergent backward, strongly convergent backward at proximal four-fifths, the maximum width 2.58 mm; transverse suture protruding to the back edge of the cephalic plate in an arc; six or seven setae on each side of back, punctate depressions interspersed throughout; dorsal side of cephalic plate with scattered puncta. Antennae 5.35 × as long as the head width. Apical sensilla at the actual distal apex of article XIV ~ 8 μm long.

Clypeus (Fig. 5 D ): clypeal ratio (areolate part / non-areolate part) ~ 1; each side bearing two or three insulae, each circumscribing one seta; transverse suture of the clypeal plagulae slightly protruding from the front cephalic plate, concave inward near cephalic pleurite, sensilla absent.

Labrum (Fig. 5 D ): anterior ala medial margin ~ 5 / 12 of length of posterior ala; the middle piece protrudes forward into a vertex over side pieces; posterior margin of side pieces curved, concave with respect to straight anterior margin; the hair-like fringes and projections on the labral side pieces absent, the comma-shaped sclerite lateral to the labral side pieces present.

Cephalic pleurite (Fig. 5 E ): spiculum present; a group of setae only on the posterior 1 / 2.

Mandible (Fig. 5 F ): approximately six well developed lamellae; first lamella with six teeth; average intermediate lamella with ~ 22 teeth, all teeth of similar size, the region before the first lamella without teeth.

First maxillae (Fig. 5 G ): antero-external corners of coxosternite protruding and short; coxosternite divided by mid-longitudinal sulcus, three to four setigerous insulae on each side; coxal projections 1.1 × as wide as long, nine setae on medial margin; clavate lappets present on coxal projections; telopodites 2.14 × as long as wide, clavate lappet present.

Second maxillae (Fig. 5 G ): sclerotic ridge on the middle of coxosternite with two setigerous insulae on the posterior ridge; each side of coxosternite with at least 17 setigerous insulae on the posterior side; telopodite article I 3.85 × as long as wide, the ventral and dorsal part of anterior telopodites both with five vertical setae; anterior article II with ten surrounding setae; article III 2.75 × as long as wide, apex densely setose, pretarsus present.

Forcipular segment (Fig. 6 A – C ): exposed part of coxosternite width-to-length radio 1.4; cerrus only composed of two convergent rows of setae. Trochanteroprefemur length-to-width radio 1.43, proximal tooth slightly smaller than the distal tooth; both femur and tibia with one tooth and the former smaller than the latter; tarsungulum with two dark brown and small basal teeth, one dorsal to the other; poison calyx reaching the distal part of trochanteroprefemur.

Leg-bearing segments (Fig. 6 D, E ): 49 leg-bearing segments; a few sternites in the anterior part of leg-bearing segment with sternal sulcus and dispersed setae; sternal sulcus of anterior segments furcate, branches at an obtuse angle; the first pair of legs much smaller than the rest, apical claw simple.

Ultimate leg-bearing segment (Fig. 6 F – I ): metasternite trapezoid in shape and with a small pillow-like protrusion in the end, length-to-width radio of 1.45; each coxopleura covered by a dense pore-field except for the distal end; ultimate leg telopodite with short setae, apical claw absent; the last leg-bearing segment covered with setae.

Postpedal segments (Fig. 6 F, H, I ): male gonopods tapered and biarticulated.

Variation in paratypes.

Body length up to 69 mm, cephalic plate length-to-width ratio 1.84–1.97, antennae length to head width ratio 3.57–5.17, medial projection of first maxillae width to length ratio 1.07–1.29 and telopodites length to width ratio 2.5–4.8, telopodites article I of second maxillae length-to-width radio 3.43–4.29, article III ratio 4–4.29, forcipular trochanteroprefemur length-to-width ratio 1.16–1.19, exposed part of coxosternite length to width ratio 0.69–0.75. The end of female metasternite also with a small pillow-like protrusion. Females gonopods also biarticulated.

Remarks.

This new species resembles M. lanzai Matic & Dărăbanțu (1969) in the furcate sternal sulci, three pairs of setae on the clypeus, and a cluster of setae located exclusively on the posterior 1 / 2 of the cephalic pleurite (Table 5 ). However, a distinguishing feature of M. lanzai is the absence of a basal tooth on the tarsungulum.

Mecistocephalus huangi sp. nov. exhibits a clear morphological resemblance with M. chuensis sp. nov. However, it can be differentiated from the latter by the presence of five to six smooth insulae on the clypeus of the former and a pillow-like protrusion on the metasternite which is common in both paratypes and non-type material of M. huangi sp. nov. (Figs 5 E , 6 F – I ). Furthermore, this species and M. chuensis sp. nov. were found to form two distinct but closely related clades in the phylogenetic analysis (Fig. 2 ).

Distribution.

China (Yunnan).

Etymology.

The specific name is dedicated to Dr. Luqi Huang for his generous help in the intensive fieldwork for collecting specimens of geophilomorphs.

Figures

Figure 2. Phylogenetic tree based on COI for Mecistocephalus with Bayesian posterior probability (PP > 0.9 / BS > 70 %, PP marked in the left and BS in the right) values and bootstrap support following ML analysis for each node and the result of species delimitation of single locus COI are based on using three species delimitation methods ABGD, PTP (ML), and PTP (BI).

Figure 5. Mecistocephalus huangi Jiang & You, sp. nov., holotype (CMMI 20201022122) A anterior part of body, dorsal view B anterior part of body, ventral view C cephalic plate, dorsal view D anterior part of head, ventral view (maxillae removed) E cephalic plate, ventral view (maxillae removed) F mandible G maxillae, ventral view. Scale bars: 50 μm (F); 1 mm (A – E, G). Part of areolation not drawn.

Figure 6. Mecistocephalus huangi Jiang & You, sp. nov., holotype (CMMI 20201022122) A forcipular segment, ventral view B forcipular segment, dorsal view C part of right forcipule, ventral view D sternite of leg-bearing segment VI, ventral view E tergites of leg-bearing segments VI – VIII, dorsal view F ultimate leg-bearing segment, ventral view G ultimate leg-bearing segment, dorsal view H ultimate leg-bearing segment and left leg, ventral view I ultimate leg-bearing segment, ventral view (paratype CMMI 20230803003 D). Scale bars: 100 μm (C); 500 μm (I); 1 mm (A, B, D-H).