Crossodonthina quadridentata, Jiang & Wang, 2024

Jiang, Ji-Gang & Wang, Qing-Yun, 2024, Species groups of Crossodonthina Yosii (Collembola: Neanuridae), with the description of a new species and a new record for C. bidentata Luo & Chen, Zootaxa 5471 (2), pp. 241-252 : 242-249

publication ID	https://doi.org/ 10.11646/zootaxa.5471.2.4
publication LSID	lsid:zoobank.org:pub:537CE1BA-3846-43D6-BBC4-545318B452D0
DOI	https://doi.org/10.5281/zenodo.12209654
persistent identifier	https://treatment.plazi.org/id/039987F6-FF99-FFA2-FF37-F97DAC8DFE4D
treatment provided by	Plazi
scientific name	Crossodonthina quadridentata
status	sp. nov.

Treatment

Crossodonthina quadridentata sp. nov.

Figs 1 View FIGURES 1–2 , 3–10 View FIGURES 3–6 View FIGURES 7–8 View FIGURE 9 View FIGURE 10 , Tables 1–3 View TABLE 1 View TABLE 2 View TABLE 3

Type material. Holotype: Female , the First Peak between Hunan and Guangdong Provinces , Nanling National Forest Park, Guangdong Province, China, coordinates: 24°55’37”N, 112°59’02”E, alt. 1645m, under leaves near a small stream in forest, leg. Ji-Gang Jiang, Yu-Yao Zhao, Fang-Jun Chen, 7.iv.2018 (J2018040707) GoogleMaps . Paratypes: two females, same data as the holotype. Type materials are deposited at the Key Laboratory of Zoology, Hunan University of Arts and Science ( HUAS), Changde, Hunan Province, China GoogleMaps .

Etymology. The name of the species is derived from Latin quadri- and dentes, due to the presence of four basal teeth on the mandible.

Diagnosis. Two eyes per side on head; cephalic chaeta O present; tubercles on body well differentiated; cephalic tubercles Dl, L and So fused; mandible with 4 basal teeth and five fringed rami; maxilla with two lamellae, the outer lamella terminally bifurcated, the inner one with a tooth and apical filaments; labral chaetotaxy formula as 4/4, 2.

Description. Body length: holotype 2.4mm, paratypes 2.2–2.6 mm. Color: living specimens red, whitish in ethanol ( Fig. 1 View FIGURES 1–2 ).

Chaetal morphology. Dorsal ordinary chaetae of five types. Long macrochaetae (Ml) pointed and smooth ( Fig. 3 View FIGURES 3–6 ). Short macrochaetae (Mc) morphologically similar to and shorter than Ml. Very short macrochaetae (Mcc) similar to and shorter than Mc. Mesochaetae (me) on the backside usually thicker than those on the ventral side. All me smooth, pointed and with variable lengths ( Fig. 3 View FIGURES 3–6 ). Microchaetae (mi) similar to me, with about half the length of the shortest me (chaeta Oca). S-chaetae (s) on terga thin, smooth, usually shorter than Mc and longer than or subequal to Mcc ( Fig. 3 View FIGURES 3–6 ).

Head. Eyes 2+2, uncolored, one anterior, but not included in Oc tubercle, the other one on the posterior part of Oc tubercle.

Antenna four-segmented ( Fig. 4 View FIGURES 3–6 ). Ant. I with 8 chaetae. Ant. II with 11 chaetae. Ant. III dorsally fused to Ant. IV. Guard chaeta sgd of Ant. III not migrated distally, almost at the same level as the exposed in separate pits two sensory rods.Ant. IV dorsally with eight subequal, slightly thickened and blunt sensilla (S1–8), apical bulb trilobed, organite (or) present. Ventral side of Ant. IV with some pointed or slightly blunt chaetae ( Fig. 5 View FIGURES 3–6 ). On ventral side of Ant. III, Vi, Vc and Ve with 4, 4, 5 chaetae respectively ( Fig. 5 View FIGURES 3–6 ).

Oral cone short, labrum truncated, labral formula as 4/4, 2 ( Fig. 6 View FIGURES 3–6 ). Labium with 11 chaetae, with two papillae x. Mandible complex ( Fig. 7 View FIGURES 7–8 ) consisting of four basal teeth, four short fringed rami, each ramus with long filaments, and a very long ramus, with two rows of marginal filaments. Maxilla consisting of two lamellae, outer lamella apically bifurcated, inner one with a tooth and short filaments ( Fig. 8 View FIGURES 7–8 ).

Cephalic dorsal tubercles and chaetotaxy as in Table 1 View TABLE 1 and Fig. 9 View FIGURE 9 . Central area of head with six tubercles: one Cl, one Fr, two Oc and two An; chaeta O free from tubercle Fr. Dorso-posterior area with four separate tubercles: two Di and two De, Di2 and De 2 mi on tubercle De. Line of chaetae Di1–De1 crossing line Di2–De2 on head (crosstype). Tubercles Dl, L and So on dorsal lateral area fused, with 10 chaetae each; two additional chaetae close to, but outside the tubercle.

Ventral chaetotaxy of head. Group Vi with six chaetae, groups Vea with four, Vem with three and Vep with three chaetae, respectively.

Thorax ( Fig. 9 View FIGURE 9 and Table 2 View TABLE 2 ). Th. I with 3+3 tubercles, Di, De, Dl with 1, 2, 1 chaetae respectively. Th. II with 4+4 tubercles, Di with three, De with four (3+s), Dl with four (2+s+ms), and L with three chaetae, respectively. Th. III with 4+4 tubercles, Di with three, De with five (4+s), Dl with four (2+s), and L with three chaetae, respectively. Chaetotaxy of thorax and legs as in Table 2 View TABLE 2 . Unguis with a basal inner tooth; unguiculus absent. Chaeta M present on tibiotarsus.

Abdomen ( Figs 9–10 View FIGURE 9 View FIGURE 10 and Table 2 View TABLE 2 ). Abd. I–III with 4+4 tubercles each, Di with two, De with four (3+s), Dl with two and L with three chaetae, respectively. Abd. IV with 4+4 tubercles, Di with two, De with three (2+s), Dl with three and L with six chaetae, respectively. Abd. V dorsally with 2+2 tubercles, two Di separated, each one with three chaetae, tubercles De and Dl fused, with five chaetae (4+s) each. Abd. VI with one tubercle with seven chaetae on each side ( Fig. 9 View FIGURE 9 ). VT with 4+4 chaetae ( Fig. 10 View FIGURE 10 ). Furcular remnant with four chaetae ( Fig. 10 View FIGURE 10 ).

Ecology. The new species lives in the forest litter.

Remarks. So far, including the new species, five species of Crossodonthina with 2+2 eyes have been reported, all from Asia. They are: C. bidentata from Zhejiang, C. hainana Xiong, Chen & Yin, 2005 from Hainan, C. montana Lee & Kim, 1990 from Taiwan, C. langshanensis Hu, Jiang & Jiang, 2019 from Hunan and C. quadridentata sp. nov. herein described.

Morphologically, C. quadridentata sp. nov. resembles C. langshanensis in the similar arrangement of body dorsal tubercles and chaetotaxy, presence of O chaeta on head, separate Di tubercles on Abd. V and usually the presence of four chaetae on the furcular remnant. However, the new species can be distinguished from the latter by the following features: structure of mandible (mandible with four basal teeth and the longest ramus with apical filaments in C. quadridentata sp. nov., mandible with two basal teeth and the longest ramus without apical filaments in C. langshanensis ), structure of maxilla (the outer bifurcate lamella and the inner fringed lamella in C. quadridentata sp. nov., the outer lamella fringed and the inner with two teeth in C. langshanensis ,), and the shape of body chaetae (all body macrochaetae pointed in C. quadridentata sp. nov., all macrochaetae slightly blunt in C. langshanensis ).

The new species is also similar to C. hainana and C. montana in the arrangement of body tubercles, the presence of O chaeta on head, the separate tubercles Di of Abd. V and the presence of 4+4 chaetae on VT. However, the new species can be separated from C. hainana by its mandible with four basal teeth (five in C. hainana ), maxilla outer lamella bifurcated (quadrifurcated in C. hainana ), cephalic tubercle Oc with three chaetae (two in C. hainana ), and chaeta O not included in the Fr tubercle (chaeta O included in the Fr tubercle in C. hainana ). Crossodonthina quadridentata sp. nov. can also be easily distinguished from C. montana by the number of mandible’s basal teeth (4 versus 1), shape of maxilla outer lamella (bifurcated versus trifurcated), and chaetae number on DI tubercle of Th. III (2+s versus 3+s).

Compared to C. bidentata , the new species has separated Di tubercles on Abd. V (fused in C. bidentata ) and four basal teeth on the mandible (two in C. bidentata ).

The differentiated characters between C. quadridentata sp. nov. and other two-eyed species are given in Table 3 View TABLE 3 .