Retrorsia gracilis 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 : 100-101

Retrorsia gracilis Shear & Marek , n. sp.

Figs 47–49 , 124, 125

Types. Male holotype and male and female paratypes from Lewis Co., Washington, 604 Roswell Road , Centralia , 46.7223°, -122.9444°, collected 25 January 2004 by W. Leonard and C. Richart. All types deposited in CAS .

Diagnosis. The pulvillus (p, Fig. 49 ) is displaced to the distal one-fifth of the gonopod, with the pulvillar notch (rn, Fig. 49 ) immediately distal. The retrorse process (rp, Fig. 49 ) is sharply recurved. There are 18 setae in the anterior marginal row of the collum.

Etymology. The species name, an adjective, refers to the slender gonopods.

Description. Male holotype. Length 4.5 mm, greatest width 0.5 mm. Anterior metazonites with three rows of setae, distribution irregular on seventh ring, transitioning to four rows ( Fig. 50 ) on eighth and ninth ring; a few posterior segments may appear to have five rows due to intercalated setae. Epiproct not swollen, short. Anterior legs crassate, tarsi with sphaerotrichomes. Gonopod ( Figs 47–49 , 124, 125 ) with large, inflated prefemorite. Acropodite long, slender, pulvillus (p, Fig. 49 ) in distal fifth of acropodite, pulvillar notch immediately distal. Retrorse process of terminal zone strongly decurved (rp, Fig. 49 , relatively long. Subterminal process (st, Fig. 49 ) with small tooth subdistally. Females similar to males in nonsexual characters.

Distribution. Lewis Co., Washington.

Records: WASHINGTON: Lewis Co.: Iron Creek Campground, 9.6 mi south of Rendell on FS25, Gifford Pinchot National Forest, 45.4297°, -121.9869°, 21 December 2003, W. Leonard, m ff; North Fork Newaukam River, below confluence with Middle Fork, 46.6046°, -122.8482°, 29 December 2004, W. Leonard, m ff.

Figures

FIGURES 45–49. Species of Retrorsia. 45, 46. Retrorsia richarti, new species. 45, Male, lateral view. 46. Gonopods in situ, lateral view. SEM stub 33-1. 47–49. Retrorsia gracilis, n. sp. 47. Gonopods in situ, anterior view. 47. The same, lateral view, anterior to the left. 49. Gonopod tip. SEM stub WS33-2. Abbreviations: p, pulvillus; rn, rounded notch distal to pulvillus; rp, retrorse process; st, subterminal process; tz, terminal zone.

FIGURES 121–126. Drawings of gonopods of polydesmid species. 121. Left gonopod of Retrorisia leonardi, mesal view. 122. Left gonopod of Retrorsia benedictae, mesal view. 123. Left gonopod of Retrorsia richarti,n. sp., mesal view. 124. Right gonopod of Retrorsia gracilis, n. sp., lateral view. 125, Gonopod tip of Retrorsia gracilis, mesal view. 126. Right gonopod of Retrorsia simplicissima, n. sp., lateral view.

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.