Mecistocephalus chuensis 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 chuensis Jiang & You sp. nov.

Figs 3 , 4

Material examined.

Holotype. • ♂; ( CMMI 20210409134 ); China, Hubei Province, Jingshan County, Kongshandong Scenic Area ; 30.9735 ° N, 113.0377 ° E; 110 m a. s. l.; 9 Apr. 2021; coll. Tianyun Chen & Zhidong Wang . Paratypes. • 2 ♂♂, 2 ♀♀; ( CMMI 20210409130 -133); same data as holotype . • 1 ♂, 7 ♀♀; ( CMMI 20210408121 -20210408124, - 129, - 131, - 132, - 134); Hubei Province, Wuhan, Ma’anshan Forest Park; 30.5146 ° N, 114.4394 ° E; 110 m a. s. l.; 8 Apr. 2021; coll. Tianyun Chen & Zhidong Wang . • 1 ♀ ( CMMI 202100121008 ); Hunan Province, Hengyang, Chuanshan Ave ; 30.5146 ° N, 114.4394 ° E; 120 m a. s. l.; 12 Jan. 2021; coll. Chao Jiang .

Diagnosis.

A Mecistocephalus species with 49 leg pairs. Head length-to-width ratio 1.77, each side of clypeus with five or six smooth insulae, clypeal ratio (areolate part / non-areolate part) of 1.22, sensilla on plagulae absent, posterior 1 / 2 of cephalic pleurite bearing a group of setae, forcipular cerrus composed of two paramedian rows of setae, mandible with ~ 8 well-developed lamellae, and first lamella with seven teeth. Sternal sulcus furcated at an obtuse angle.

Description.

Holotype ( CMMI 20210409134 ).

Body length: 58 mm; posterior part slightly slender. Head and forcipular segment dark red in color; remainder yellow.

Cephalic plate (Fig. 3 A-C ): sub-rectangular, length-to-width ratio of 1.77; lateral margins slightly convergent backward, strongly convergent backward at proximal three-fourths, maximum width 2.88 mm; transverse suture protrudes to the back edge of the cephalic plate in an arc; two or three setae in the anterior of back side, punctate depressions interspersed throughout. Antennae 5.3 × as long as the head width. Apical sensilla ~ 8 μm long.

Clypeus (Fig. 3 D ): clypeal ratio (areolate part / non-areolate part) ~ 1.22; five or six insulae on each side of clypeus, only four bearing setae on each side; the transverse suture of clypeal plagulae almost straight, sensilla inside plagulae absent.

Labrum (Fig. 3 D ): anterior ala with medial margin not reduced to a vertex, medial margin ~ 1 / 3 of the length of posterior ala; mid piece protruding forward over side pieces; posterior margin of side pieces sinuous, concave or convex 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. 3 E ): spiculum present, group of setae only on the posterior 1 / 2.

Mandible (Fig. 3 F ): approximately eight well-developed lamellae; first lamella with seven teeth; average intermediate lamella with ~ 22 teeth; basal teeth as same size as distal teeth; basal tooth large, shorter than the teeth of the first lamella.

First maxillae (Fig. 3 G ): antero-external corners of coxosternite protruding and short; coxosternite divided by mid-longitudinal sulcus, with eight or nine setigerous insulae on each side; coxal projection 1.2 × wider than long, eleven setae on medial marginal and clavate lappet present; telopodites 2.86 × longer than wide, clavate lappet present.

Second maxillae (Fig. 3 G ): sclerotic ridge on the middle of coxosternite circumscribing three or four setigerous insulae; each side of coxosternite with setae on the lateral to each metameric pore; telopodite article I 1.4 × longer than wide; anterior end of article II with six surrounding setae; article III 2.78 × longer than wide, with distal end densely setose, pretarsus present, conical in shape.

Forcipular segment (Fig. 4 A, B ): exposed part of the coxosternite with a width-to-length ratio of 0.68; cerrus composed of two convergent rows of setae and a pair of setae on each side. Forcipular trochanteroprefemur length-to-width ratio of 1.7, proximal tooth slightly smaller than the distal tooth; femur and tibia each with one tooth, equal in size; tarsungulum with two dark brown, small. basal teeth, one dorsal to the other.

Leg-bearing segments (Fig. 4 C, D ): 49 leg-bearing segments; a few sternites with sternal sulcus and dispersed setae; sternal sulcus of anterior segments furcate, branches at an obtuse angle.

Ultimate leg-bearing segment (Fig. 4 E – H ): metasternite trapezoidal, length-to-width ratio of 1; each coxopleuron covered with dense pore-field into the distal end ultimate leg telopodite with short setae, apical claw absent.

Postpedal segments (Fig. 4 E, G, H ): male gonopods tapered and biarticulated.

Variation in paratypes.

Body length up to 64 mm, cephalic plate length-to-width ratio of 1.77–1.97, antennae length-to-head width ratio of 4.8–5.5, medial projection of first maxillae width-to-length ratio of 1.2–2.14 and telopodites length-to-width ratio of 1.43–2.86, telopodites article I of second maxillae length-to-width ratio of 4–6.88, article III ratio of 2.78–3.18, forcipular trochanteroprefemur length-to-width ratio of 1.27–1.7, exposed part of coxosternite length-to-width ratio of 0.68–0.79. Female gonopods also biarticulated.

Remarks.

As shown in Table 5 , M. megittii Verhoeff, 1937 , M. stenoceps Chamberlin, 1944 , M. enigmus Chamberlin, 1944 and M. chuensis sp. nov. are similar in the numbers of leg-bearing segments, furcate sternal sulcus and clypeal ratio, but other features distinguish them. Mecistocephalus megittii notably differs from M. chuensis sp. nov. in the presence of a large tooth on the tarsungulum (only a small tooth at the base of the tarsungulum in the latter) and the presence of one or two setae on each side of clypeus (3 setae on each side of clypeus in the latter) ( Attems 1947).

Similarly, the other two species and M. chuensis sp. nov. can be distinguished by the location of the setae and presence or absence of a tooth on the forcipular femur. The clypeus of M. stenoceps Chamberlin has a series of three setae in a transverse row on each side farther anteriorly than in M. chuensis sp. nov., and M. enigmus lacks a femoral tooth ( Chamberlin 1944), which is present in M. chuensis sp. nov.

Distribution.

China (Hubei, Hunan).

Etymology.

The specific name is derived from its distribution in Hunan Province and Hubei Province, where “ Chu ” in ancient China usually referred to these regions.

Figures

Figure 3. Mecistocephalus chuensis Jiang & You, sp. nov., holotype (CMMI 20210409134) A anterior part of body, dorsal view (right antenna not drawn) B anterior part of body, ventral view (right antenna not drawn) 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 and inner illustration shows the telopodite article III of the second maxillae, ventral view (right telopodite of the second maxillae removed) Part of areolation not drawn. Scale bars: 20 μm (F); 1 mm (A-E, G).

Figure 4. Mecistocephalus chuensis Jiang & You, sp. nov., holotype (CMMI 20210409134) A forcipular segment, ventral view B forcipular segment, dorsal view C sternite of leg-bearing segment VI, ventral view D tergites of leg-bearing segments VI-VIII, dorsal view E ultimate leg-bearing segment, ventral view F ultimate leg-bearing segment, dorsal view G ultimate leg-bearing segment and left leg, ventral view H ultimate leg-bearing segment, ventral view (paratype CMMI 20210408122). Scale bars: 500 μm (H); 1 mm (A-G).