Nearctomeris smoky, Recuero & Caterino, 2023

Recuero, Ernesto & Caterino, Michael S., 2023, A second species of the pill millipede genus Nearctomeris Wesener, 2012 (Diplopoda, Glomerida) from the Great Smoky Mountains, USA, ZooKeys 1166, pp. 333-349 : 333

Nearctomeris smoky sp. nov.

Figs 3 , 4 , 5

Type material.

Holotype: male (USNM ENT01838998; Fig. 3 ), USA, Tennessee, Blount Co., Great Smoky Mountains N. P., Whiteoak Sink; 35.6369°N, 83.7418°W; in leaf litter at base of rock; leg. M. Caterino, A. Haberski & P. Wooden, 27.x.2021. Paratypes: 2 males (CUAC000180803, GRSM217979), 2 females (USNM ENT01838999, GRSM217980) and 5 juveniles (CUAC000180807-CUAC000180810, GRSM217981), same data as holotype.

Diagnosis.

Externally similar to Nearctomeris inexpectata ; they can be differentiated in the shape of the femoral process (distal finger) of telopods (Fig. 5E ), blunt and rounded in N. inexpectata , elongated and curved in the N. smoky sp. nov., and of the syncoxite (Fig. 5D ), distally broader in N. inexpectata than in N. smoky sp. nov., with rounded central lobe in N. inexpectata and bilobed in N. smoky sp. nov., and lateral processes shorter in N. inexpectata than in N. smoky sp. nov. The observed mean COI pairwise uncorrected p-distance between both species is 6.85%.

Name.

Smoky, a noun in apposition, refers to the Great Smoky Mountains where the species lives.

Description.

Body with 12 segments (including collum). Length of largest male (holotype), 2.9 mm; width at thoracic shield 1.8 mm, at tergite five 2 mm; height of thoracic shield 1.3 mm. Length of largest female 3.2 mm; width at thoracic shield 2 mm, at tergite five 2.1 mm; height of thoracic shield 1.3 mm.

General coloration of adults (Fig. 3 ) brown to dark brown dorsally; collum with a large, central, off-white area; tergites 2-11 with lateral, transversely oval, off-white areas; lateral and posterior margins of tergites translucent; head brown, more or less mottled with white, labrum and organ of Tömösváry white, ocular field black; antennae brown mottled with white; ventrally off-white, legs white, mottled or not with brown, with brown tarsi. Juveniles with 11 segments with similar pattern but much lighter than adults, and even lighter in juveniles with 10 segments (Fig. 4A ).

Head (Fig. 3B ): structure typical of Nearctomeris , without any distinct crest or groove. Ommatidia 5+1 or 4+1, unpigmented, within a black, elongate ocular field. Tömösváry’s organ transverse, horseshoe-shaped, about 2 times as wide as long. Antennae with antennomere 3 shorter than 1 and 2 combined; four apical cones.

Collum (Fig. 4B ): surface smooth, finely and densely punctured dorsally with minute pits, as the rest of segments, with two well-marked, transverse striae.

Thoracic shield (Fig. 4B ): with schisms rounded posteriorly, well-differentiated but not protruding beyond tergite contour. Schism impression broad and well-developed. Only three striae transversely crossing the shield; no trace of a central, incomplete stria. One strong, one very weak lateral stria below the schism impression.

Tergites (Figs 3A , 4A ): with soft, shiny appearance; surface densely covered with small pits that, observed through the transparent first layer of the tegument, seem to be the opening of pore canals connecting the epidermis with the exterior. There is no trace of setae on the tergites. Tergite 11 is partially hidden under tergite 10.

Mid-body legs (Fig. 5A ): relatively slender, femur about 2.5 times as long as wide, tarsus 5-5.5 times as long as wide. Ventral margin of prefemur and femur with numerous strong setae. Tarsus with 5-6 ventral, 2-3 dorsal spiniform setae, mostly set in the distal half. Claw 4-4.5 times as long as wide.

Anal shield (Fig. 3B ): with evenly rounded posterior border, with no sign of a notch or concavity.

Male leg pair 17 (Fig. 5B ): with a broad coxal lobe, mesally with a spiniform seta; telopodite formed by three strongly reduced podomeres, first and second with mesal spiniform setae, third with an apical spiniform seta.

Male leg pair 18 (Fig. 5C ): with no obvious syncoxial notch; coxa with a spiniform seta; 4-segmented telopodite, reduced but better developed than in leg pair 17. First, second and third podomeres with mesal spiniform setae, apical in fourth podomere.

Telopod (Fig. 5D-F ): robustly developed; syncoxite (Fig. 5D ) with a long, subrectangular central lobe (cL) with bilobed distal margin, flanking lateral processes (h) longer than the lobe and carrying long, strong, mesoproximal setae and a spiniform mesodistal seta. Prefemur trichostele (Fig. 5E, F ; Pre-tri) about as long as prefemur width. Femur trichostele (Fig. 5E ; Fem-tri) about two thirds as long as the prefemoral one. Femoral process (distal finger) (Fig. 5E, F ; Fem-pr) broad at base, distal half much narrower and distal third curved anteriad. Fields of sclerotized scale-like structures present on femoral distal finger and tibia (Fig. 5F ). Tarsus strong, blunt and curved, with a strong, apical spine.

Figures

Figure 3. Nearctomeris smoky sp. nov., habitus of male holotype (USNM) A lateral view B ventral view.

Figure 4. Nearctomeris smoky sp. nov. A habitus of a 10 - segment juvenile (CUAC) in lateral and ventral views B SEM image of collum and thoracic shield of a female (USNM), showing details of tegument, striae and schism.

Figure 5. Nearctomeris smoky sp. nov., holotype (USNM) A male left leg 11, anterior view B male leg pair 17, anterior view C male left leg 18, anterior view D telopod syncoxite, anterior view E left telopod, anterior view F left telopod, posterior view. Abbreviations: cL = syncoxite central lobe; Fem-pr = telopod femoral process; Fem-tri = telopod femoral trichostele; h = syncoxite lateral process; Pre-tri = telopod prefemoral trichostele.