Retrorsioides castellum 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 : 103-105

Retrorsioides castellum Shear & Marek , n. sp.

Figs 53–58 , 127

Types. Male holotype and male paratypes from Delemeter Road , 10.1 mi southwest of Castle Rock , 46.2175°, - 123.0178°, 400 ft asl, Cowlitz Co. Washington, collected 23 November 2003, by W. Leonard and C. Richart. All types deposited in CAS .

Diagnosis. The anteriorly directed process of the gonopod (adp, Fig. 56 ) is about as long as the terminal zone, thin and acute; the pulvillar process (pp, Figs 56, 57 ) is in the form of a blunt tooth; the terminal zone (tz, Fig. 56 ) is simple and curved. The anterior marginal row of setae on the collum consists of 24–26 setae; anterior metazonites have 4 rows of setae.

Etymology. The species name, a noun in apposition means “castle” in Latin and refers to the town of Castle Rock, near the type locality.

Description. Male holotype. Length about 6.0 mm, greatest width 0.8 mm. Head densely setose, cuticle alveolate ( Fig. 53 ). Collum ( Fig. 53 ) with anterior marginal row of 24 setae (26 in some paratypes). Anterior metazonites with four rows of setae ( Figs 53, 54 ), a few posterior segments may appear to have five rows due to intercalated setae; setal tubercles becoming low on posterior segments. Epiproct ( Fig. 55 ) not swollen, short. Anterior legs crassate, tarsi with sphaerotrichomes. Gonopod ( Figs 56, 57 , 127 ) with subglobular prefemorite. Acropodite relatively long, narrow. Pulvillus (p, Figs 56, 57 ) in distal third of acropodite, pulvillar process (pp, Fig. 56 ) a short, slightly curved tooth. Anteriorly directed process (adp, Fig. 56 ) long, evenly tapering. Terminal zone (tz, Fig. 56 ) simple, curved. Females similar to males in nonsexual characters; vulvae as in Fig. 58 .

Distribution. Cowlitz Co., Washington.

Records: WASHINGTON: Cowlitz Co.: Germany Creek at end of county road, 5.5 mi north of Stella, 46.2564°, -123.1345°, 450 ft asl, 27 November 2003, W. Leonard, C. Richart, m ; Germany Creek , 5.5 mi north of SR4, 47.2608°, -123.1343°, 350 ft asl, 8 December 2003, W. Leonard, mm f .

Note: at the Germany Creek localities, this species is syntopic with Retrorsia richarti , n. sp. It is almost 50% larger. There is a region of wrinkled, seemingly less sclerotized cuticle at the base of the anteriorly directed process ( Fig. 56 ), suggesting that this feature might be movable. Figure 56 shows a probable spermatic mass exuded from the pore of the pulvillus. Millipedes do not produce motile sperm.

Figures

FIGURES 50–55. Species of Retrorsia and Retrorsioides, n. gen. 50–52. Retrorsia simplicissima, n. sp. 50. Head and anterior rings, dorsal view. 51. Midbody ring, dorsal view. 52. Pygidium, lateral view. SEM stub WS33-11. 53–55. Retrorsioides castellum, n. sp. 53. Head and anterior rings, dorsal view. 53. Midbody ring, dorsal view. 55. Pygidium, lateral view. SEM stub WS32-17.

FIGURES 56–60. Species of Retrorsioides, n. gen.. 56–58. Retrorsioides castellum, n. sp. 56. Gonopods, lateral view, anterior to the right. 57. Pulvillus with probable spermatic mass.58. Female genitalia, ventral view. SEM stub WS32-17. 59, 60. Retrorsioides linnensis, n. sp. 59. Midbody ring, dorsal view. 60. Tip of antenna, apical view. SEM stub WS33-15. Abbreviations: adp, anteriorly directed process; p, pulvillus; pp, pulvillar process.

FIGURES 127–132. Drawings of gonopods of polydesmid species. 127. Tip of gonopod of Retrorsioides castellum, n. sp., mesal view. 128. Right gonopod of Retrorsioides linnensis, n. sp., lateral view. 129. Left gonopod of Retrorsioides kittitas, n. sp., lateral view. 130. Right gonopod of Retrorsioides bannerti, n. sp., lateral view. 131. Right gonopod of Rowlandesmus millicoma, n. sp., mesal view. 132. Right gonopod of Rowlandesmus dentogonopus, n. sp., lateral view. Abbreviations: adp, anteriorly directed process; p, pulvillus; pf, prefemorite; pp, pulvillar process; tz, terminal zone.