The second Mecistocephalus centipede without a spiculum: Mecistocephalus aspiculus sp. n. from south China (Chilopoda: Geophilomorpha: Mecistocephalidae) Author Zhao, Yiying Tianjin Key Laboratory of Agricultural Animal Breeding and Healthy Husbandry, College of Animal Science and Veterinary Medicine, Tianjin Agricultural University, Tianjin, China; Author You, Chunxue Tianjin Key Laboratory of Agricultural Animal Breeding and Healthy Husbandry, College of Animal Science and Veterinary Medicine, Tianjin Agricultural University, Tianjin, China; Author Jiang, Chao State Key Laboratory for Quality Ensurance and Sustainable Use of Dao-di Herbs, National Resource Center for Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, China text Journal of Natural History 2024 J. Nat. Hist. 2024-08-12 58 29 - 32 1282 1292 http://dx.doi.org/10.1080/00222933.2024.2380454 journal article 10.1080/00222933.2024.2380454 1464-5262 13758213 E6A2551E-3B7C-4FB7-B603-F2EFA560A576 Mecistocephalus aspiculus Jiang and You , sp. n. ( Figures 1–3 , Table 1 ) Chinese name: 无锥齿地蜈蚣 urn:lsid:zoobank.org:pub: E6A2551E-3B7C-4FB7-B603-F2EFA560A576 Material examined. Holotype . 1 male , Xinfengjiang Reservoir , Xingang Town , Heyuan City , Guangdong Province , China , 23.7703°N , 114.6301°E , 180 m asl ., 17 December 2020 , leg. Zhidong Wang (labelled as CMMI-20201217113). Diagnosis. A Mecistocephalus species with 49 leg-bearing segments. Spiculum absent. Labrum without hairs; a pair of comma-shaped sclerites present lateral to the side-pieces. Telopodites of the first maxillae with sub-trapezoid hyaline end lobes. Coxosternite of the second maxillae undivided; metameric pore surrounded by foraminal process separated from the coxosternite. Telopodites of the second maxillae reaching those of the first maxillae, with a distinct projection on the outer-distal corner of basal article; claw present. Forcipular trochanteroprefemur with one tooth only. Sternal sulcus furcate. Coxopleura without macropore. Ultimate legs slender, without claw. Male gonopod biarticulated. Anal pores present. Figure 1. Mecistocephalus aspiculus sp. n. (CMMI-20201217113): a , forcipular segment and anterior leg-bearing segments, dorsal; b , median part of body, dorsal; c , posterior part of body, dorsal. Scale bar: 1 mm. Description. A total of 49 leg-bearing segments. Body length 39 mm , gradually attenuated posteriorly. Colour (of preserved specimen in alcohol): head and forcipular segment dark red, trunk homogeneously yellow, without dark patches ( Figure 1 ). Antennae ( Figure 2a ) with 14 articles, distally only slightly attenuate. Articles Ι to IV slightly asymmetrical, with internal margin longer than external margin. Articles Ⅴ to XIV symmetrical. Setae scattered on articles I to VIII, more dense and uniform in size on remaining articles. Article XIV with 15–28 claviform sensilla on the external side and 4–6 on the internal side ( Figure 2b ). Distal end of this article with 5 or 6 pin-shaped specialised sensilla (detailed description of this type of sensilla referred to in Foddai et al . 2003 ). Cephalic plate ( Figures 2c , 4a ) 1.9 times longer than wide. Transverse suture present. Paramedian sulci absent. Lateral margins nearly straight and convergent backwards, anterior margin convex, with a median incision, posterior margin straight. Setae arranged nearly symmetrically. Clypeus ( Figures 2d , 4b ) 1.6 times wider than long. Clypeal plagulae sub-trapezoid, laterally in contact with the paraclypeal sutures, separated by a mid-longitudinal areolate stripe extending along the lateral margins of the clypeus. Areolate part present along anterior half of clypeus, with about 10 pairs of setae inside several smooth insulae. The ratio of the length of the areolate and non-areolate parts (plagulae) of the clypeus is about 0.45. Figure 2. Mecistocephalus aspiculus sp. n. (CMMI-20201217113): a , right antenna, ventral; b , antennal articles XIII and XIV of right antenna, dorsal; c , cephalic capsule, dorsal; d , clypeus, labrum and anterior part of cephalic pleurite, ventral, cephalic pleurite uncovered; e , cephalic capsule, ventral (maxillary complex removed); f , maxillary complex, ventral; g , forcipular segment, ventral; h , forcipular segment, dorsal. Areolation is drawn only partially but margins of areolate regions are indicated by incomplete lines. Scale bar: 500 μm. Labrum . ( Figures 2d , 4b ) Mid-piece ca. 1.5 times longer than wide, uniformly sclerotised, posteriorly pointed. A pair of comma-shaped sclerites on the external side of side-pieces, well sclerotised. Side-pieces sub-trapezoid, divided into anterior and posterior alae by a transverse thickened line, which is convex forwards on the medial part. Anterior margin of each anterior ala sinuous, with internal margins evidently convergent backwards, external margins convergent forwards. Posterior alae of the labrum without longitudinal stripes, without setae or hair-like projections along the posterior margin. Posterior margin of each posterior ala sinuous, slightly convex close to the internal and external ends. Figure 3. Mecistocephalus aspiculus sp. n. (CMMI-20201217113): a , distal part of left mandible; b , sternite of leg-bearing segment, ventral (setae not represented); c , tergites of leg-bearing segments, dorsal; d , posterior part of trunk, ventral (with left penultimate leg and left telopodite of ultimate legbearing segment, setae on postpedal segments not represented); e , ultimate leg-bearing segment and postpedal segments, dorsal; f , ultimate leg-bearing segment and postpedal segments, ventral (setae represented only on postpedal segments). Scale bars: a, b = 100 μm; c–f = 500 μm. Cephalic pleurite ( Figure 2e ) without spiculum. Areolate part present along anterior margin and paraclypeal suture. Setae absent. Stilus present, without anterior incision ( Figure 4c ). First maxillae . ( Figure 2f ) Coxosternite ca. 1.6 times wider than long, divided by mid-longitudinal suture, with antero-external corners pointed forwards; two pairs of setae present. Coxal projections and telopodites both well developed, each comprising a sclerotised proximal half with setae and a hyaline terminal half without setae. Hyaline end lobes of telopodites curved inwards, with distal part thickened into sub-trapezoid. Table 1. Main differential characters between M. aspiculus Jiang and You , sp. n. and M. yanagiharai Takakuwa, 1936 . Character states of M. yanagiharai are based on the description and reference pictures published by Uliana et al. (2007) and Takakuwa (1936a) .

Mecistocephalus yanagiharai	Mecistocephalus aspiculus
Species	Takakuwa, 1936	Jiang and You, sp. n.
Clypeus: width/length	1.2	1.6
Clypeus: areolate part length/non-	1.45	0.45
areolate (plagulae) part length
Sensilla of clypeal plagulae	Absent	Present
Labral mid-piece: shape of posterior	Sub-fusiform	Inverted triangular
margin
Labral side-piece: shape of anterior	Almost straight, with external margins	Sinuous, with external margins
margin	slightly convergent backwards	evidently convergent forwards
Labral side-piece: shape of posterior	Straight	Convex close to the internal and
margin	external ends
Additional sclerite on the external of	Absent	Present (comma-shaped)
side-piece
First maxillary coxal projection: shape	Clavate, sub-triangular	Sub-trapezoid
of distal lobe
Article I of second maxillary	4.5	4
telopodite: length/width

Second maxillae . ( Figure 2f ) Coxosternite undivided, ca. 1.2 times longer than wide; anterior and posterior margins concave, lateral margins parallel, posterior corners only slightly projecting externally; areolation on medial and posterior part, with a few pores and setae mostly present along the posterior part. Foraminal process surrounding the metameric pore separated from lateral margin of coxosternite. Telopodites reaching the telopodites of first maxillae; article 1 of telopodite four-times longer than wide, curved outwards, with distal setae on the internal side and a distinct projection on the outer-distal corner. Article 2 of telopodite 1.4 times longer than wide, with distal setae on the internal side. Article 3 three-times longer than wide, with distal end densely setose; apical claw simple and small. Forcipular segment ( Figure 2g , h ) with setae on both dorsal and ventral surface. Forcipular tergite sub-trapezoid, 1.2 times wider than long. Coxosternite 1.2 times wider than long, anterior margin with a pair of stout teeth; scapular points of pleura not reaching the anterior margin of coxosternite. Trochanteroprefemur two-times longer than wide, with a single distal tooth. Femur, tibia and tarsungulum each with a tooth smaller than the distal tooth of trochanteroprefemur; the tooth of tarsungulum not pigmented. Tarsungulum uniformly tapering towards the tip, most of the distal part dark. Mandible ( Figure 3a ) with ca. 6 well-developed and ca. 2 rudimentary pectinate lamellae; first lamella with 6 teeth, similar in size; intermediate lamellae with 11–15 teeth, gradually decreasing in length from the distal to the basal end on each lamella. Trunk (excepting ultimate leg-bearing segment). ( Figure 3b, c ) Sternal sulci of trunk segments furcated, apparently present from the first to the fourteenth sternites (then fading into shallow and not furcated sulci), bifurcation pointed at half the total length of sulcus, angle between branches ca. 100° at the base; sternal pores absent. First pair of legs much smaller than the others. All leg claws without anterior or posterior accessory spurs. Figure 4. a–d , Mecistocephalus aspiculus sp. n. (CMMI-20201217113): a , cephalic capsule, dorsal; b , clypeus, labrum and anterior part of cephalic pleurite, ventral, cephalic pleurite uncovered; c , stilus of the right cephalic pleurite, ventral; d , ultimate leg-bearing segment and postpedal segments, ventral; e , Mecistocephalus guildingii Newport, 1843 , from Beihai, Guangxi (CMMI-20201122102): labrum, ventral; f , Mecistocephalus guildingii Newport, 1843 from Honghe, Yunnan (CMMI-20190123001): labrum, ventral; g , Mecistocephalus multidentatus Takakuwa, 1936 , from Qingyuan, Guangdong (CMMI-20240123002): labrum, ventral; h , Mecistocephalus smithii Pocock, 1895 , from Guangzhou, Guangdong (CMMI-20191014031): labrum, ventral. Scale bars: a–d = 250 μm; e, f = 50 μm; g, h = 150 μm. Ultimate leg-bearing segment . ( Figures 3d–f , 4d ) Tergite sub-rectangular, 1.4 times longer than wide. Metasternite with pillow-like process. Coxopleuron about 1.1 times as long as tergite and two-times longer than sternite.About 18 coxal pores on each coxopleuron, on ventral and lateral sides only, diverse in size but without conspicuous macropore. Setae scattered on all tergites, sternites and coxopleuron, much denser on coxopleuron. Ultimate leg telopodite 4.1 times longer than tergite and 2.2 times longer than the preceding leg pair. Telopodite of 6 articles, not swollen, with scattered setae, without pretarsus. Anal pore on each ventro-lateral side of postpedal segments. Gonopod biarticulated, with few setae; penis present. Distribution. China ( Guangdong ). Etymology. This adjective, in masculine gender, combines ‘a-’ (meaning ‘without’ or ‘lacking’ in Greek) and ‘spiculus’ (Latin for ‘small spike’ or ‘spicule’), indicating the absence of spiculum in the species. Remarks. Due to the absence of the spiculum, which refers to the sclerotised and pointed projection on the anterior part of the cephalic pleurite, the new species is easily distinguishable from all the other Mecistocephalus species , except for M. yanagiharai ( Takakuwa, 1936a ) . Table 1 highlights morphological differences between these two species. In published literature, information about the posterior half of the body is limited, because some details are not available from either text or figures of M. yanagiharai , so they are not listed in this table.