Mecistocephalus aspiculus Jiang and You, 2024

Zhao, Yiying, You, Chunxue & Jiang, Chao, 2024, The second Mecistocephalus centipede without a spiculum: Mecistocephalus aspiculus sp. n. from south China (Chilopoda: Geophilomorpha: Mecistocephalidae), Journal of Natural History (J. Nat. Hist.) 58 (29 - 32), pp. 1282-1292 : 1283-1289

publication ID	https://doi.org/ 10.1080/00222933.2024.2380454
DOI	https://doi.org/10.5281/zenodo.13785613
persistent identifier	https://treatment.plazi.org/id/03FE341C-4377-FFB8-FEAD-FBA5FD8593EC
treatment provided by	Plazi
scientific name	Mecistocephalus aspiculus Jiang and You
status	sp. nov.

Treatment

Mecistocephalus aspiculus Jiang and You , sp. n.

( Figures 1–3 View Figure 1 View Figure 2 View Figure 3 , Table 1 View 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). GoogleMaps

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.

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 View Figure 1 ).

Antennae ( Figure 2a View Figure 2 ) 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 View Figure 2 ). 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 View Figure 2 , 4a View Figure 4 ) 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 View Figure 2 , 4b View Figure 4 ) 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.

Labrum. ( Figures 2d View Figure 2 , 4b View Figure 4 ) 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.

Cephalic pleurite ( Figure 2e View Figure 2 ) without spiculum. Areolate part present along anterior margin and paraclypeal suture. Setae absent. Stilus present, without anterior incision ( Figure 4c View Figure 4 ).

First maxillae. ( Figure 2f View Figure 2 ) 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.

Second maxillae. ( Figure 2f View Figure 2 ) 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 View Figure 2 ) 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 View Figure 3 ) 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 View Figure 3 ) 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.

Ultimate leg-bearing segment. ( Figures 3d–f View Figure 3 , 4d View Figure 4 ) 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 View 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.