Retrorsioides arboramagna Shear & Marek, 2021

Shear, William A. & Marek, Paul E., 2021, Three new genera and eighteen new species of miniature polydesmid millipedes from the northwestern United States (Diplopoda, Polydesmida, Polydesmidae), Zootaxa 4975 (1), pp. 81-126 : 108-110

Retrorsioides arboramagna Shear & Marek , n. sp.

Figs 79–84

Type. Male holotype from Prairie Creek Redwoods State Park , “Big Trees,” 252 ft asl, 41.4006°, -124.0003°. Humboldt Co. California, collected 2 December 2006 by C. Richart. The holotype is mounted on SEM stub WS33-16, deposited in CAS .

Diagnosis. Distinct from other species of the genus in the extended pulvillus (p, Fig. 83 ), and a strong tooth (x, Fig. 83 ) at the base of the anteriorly directed process.

Etymology. The species epithet (Latin) is a noun in appostion meaning “big tree” and refers to the type locality, famous for its gigantic Coast Redwoods.

Description. Male holotype. Length about 3.0 mm, greatest width 0.45 mm. Head densely setose, cuticle alveolate ( Fig. 79 ). Collum ( Fig. 79 ) with anterior marginal row of 16 setae. Anterior metazonites with three rows of setae, transitioning to four rows about ring 5, setal tubercles becoming almost obsolete on midbody to posterior rings ( Fig. 80 ). Alveolate cuticle absent from metazonite posterior to collum. Epiproct ( Fig. 81 ) not swollen, short, straight, with alveolate cuticle. Anterior legs crassate, tarsi with sphaerotrichomes. Gonopod ( Figs 82–84 ) with moderately inflated prefemorite. Acropodite long, robust, basally thickened. Pulvillus (p, Fig. 83 ; Fig. 84 ) in distal third of acropodite, its dorsal side prominently extended. Pulvillar process (pp, Fig. 83 ) short, thin, directed posteriorly. Anteriorly directed process (adp, Fig. 83 ) long, tapering to acute point, without small teeth along length but with single, sharp, slightly curved tooth (x, Fig. 83 ) at base. Terminal zone (tz, Fig. 83 ) not bifurcate, flattened. Females unknown.

Distribution. Known only from the type locality.

Figures

FIGURES 79–84. Retrorsioides arboramagna, n. sp. 79. Head and anterior rings, dorsal view. 80. Midbody ring, dorsal view. 81. Pygidium, lateral view. 82. Gonopods in situ, lateroposterior view. 83. Gonopod tip, mesal view. 84. Pulvillus of gonopod. SEM stub WS33-16. Abbreviations: adp, anteriorly directed process; p, pulvillus; pp, pulvillar process; tz, terminal zone, x, unnamed gonopod process.