Pacifiosoma acutum, Mikhaljova, 2021

Mikhaljova, Elena V., 2021, The millipede family Diplomaragnidae Attems, 1907 in the Asian part of Russia with the descriptions of two new genera and seven new species (Diplopoda, Chordeumatida), Zootaxa 5060 (1), pp. 1-44 : 25-28

Pacifiosoma acutum sp. nov.

Figs 32–39

Material examined. Holotype: male ( FSCB, one posterior gonopod colpocoxite broken), Russia: Khabarovsky Krai, Ulchsky District , near Sofiysk village, Skalisty Mountain Range , green moss Picea forest, VII.1990, leg. G.N. Ganin, A. Bezborodov.

Diagnosis. Differs from congeners mainly by the plate-shaped external edge of the gonopod colpocoxite, coupled with the pointed apex of the colpocoxite.

Description. Male. Length 10–11 mm, width about 1.1 mm with paraterga. Coloration in alcohol beige (discoloration in alcohol is possible). Distal parts of anterior legs brownish. Antennae brown. Eye patches black, with about 30 ocelli.

Body with 32 rings. Collum semicircular. Both collum and ring 2 narrower than head with genae. Ring 2 somewhat wider than collum. Paraterga beginning on ring 3, well developed on rings 5–27, reduced on rings 28, onward missing. Metazonital macrochaetae in a transverse row on somites 30–31, like an extended triangle on preceding rings. Anterolateral macrochaetae shortest, clavate. Caudolateral macrochaetae longest. Medial and caudolateral macrochaetae pointed, but not very sharply so. Axial suture poorly developed.

Legs long and slender. Leg pairs 1 and 2 typically reduced in size, with usual tarsal brushes. Other pregonopodal legs practically not enlarged. Leg pairs 3–7 with several funnel–shaped tarsal papillae apically near claw. Claw of leg pairs 3–7 at base with a setoid outgrowth ventrally but without additional claws dorsally. Postgonopodal legs (including leg pairs 10 and 11) without tarsal papillae. Claw of legs 10 and 11 at base with a long setoid outgrowth ventrally and two small additional claws dorsally. Claw of midbody legs at base with two small additional claws dorsally and a long setoid outgrowth ventrally. Claw of hindmost legs at base with a long setoid outgrowth ventrally only.

Legs 10 and 11 with coxal glands. Coxae and trochanters 10 and 11 without other modifications.

Gonopods as in figs 32–39 (one posterior gonopod colpocoxite broken, however, posterior and anterior angiocoxal processes remained intact). Flagelliform anterior gonopod telopodites (at, Figs 32, 34 ) pass inside a short sheath groove with elevated edges. Distal part of the telopodites shallowly, smoothly serrated, visible as stretched beyond sheath groove. Posterior gonopod colpocoxites fused basally, their distal parts slightly curved caudally. Each colpocoxite entire, almost completely covered with dense papillae-scales. External edge of the colpocoxite as a large plate (n, Figs 36 , 39 ). Apex of the colpocoxite pointed. Colpocoxite sheath groove without evident processes. Posterior gonopod angiocoxites with moderately developed elongated subglobules in posterior view, depressed centrally in anterior view. Posterior angiocoxal process (pp, Figs 32, 36 ) large, with wide apex covered with pappilae and clawlike outgrowth (с, Fig. 33 ). Anterior angiocoxal process (ap, Figs 37, 39 ) long, flagelliform, its distal portion placed inside fold of colpocoxite, its apex extended. Posterior gonopod telopodite 2-segmented, setose; distal segment large, basal segment with a thin stem.

Female unknown.

Etymology. The specific epithet refers to the pointed apex of the gonopod colpocoxite, an adjective in apposition.

Figures

FIGURES 32–36. Pacifiosoma acutum sp. nov., male holotype. 32, 36, gonopods, caudal view, right colpocoxite broken; 33, posterior angiocoxal processes; 34, distal parts of anterior gonopod telopodite and colpocoxite; 35, external edge of colpocoxite; pp, posterior angicoxal process; n, external edge of colpocoxite; at, anterior gonopod telopodite; c, clawlike outgrowth. Scales: 10 μm (Figs 34–35), 20 μm (Fig. 33), 100 μm (Fig. 32), 0.5 mm (Fig. 36).

FIGURES 37–39. Pacifiosoma acutum sp. nov., male holotype. 37, 39, gonopods, front view, left colpocoxite broken; 38, papillae of anterior colpocoxite part; n, external edge of colpocoxite; ap, anterior angiocoxal process. Scales: 20 μm (Figs 38–39), 100 μm (Fig. 37).