Stenozonium leonardi, Shelley & Shear, 2005

Shelley, Rowland M. & Shear, William A., 2005, A new milliped of the genus Stenozonium Shelley 1998 from Washington State, U. S. A.: first record of the genus and family from North of the Columbia River (Polyzoniida: Polyzoniidae), Zootaxa 1017 (1017), pp. 25-32 : 28-31

Stenozonium leonardi , new species

Figs. 2–4.

Type specimens. ♂ holotype and juvenile paratype (North Carolina State Museum of Natural Sciences [ NCSM]) collected by W. P. Leonard and C. Richart, 5 March 2005, along Queets River Rd. ca. 6 mi (9.6 km) NE jct. US hwy. 101, in Olympic National Park , Jefferson County, Washington (N 47º 34.330', W 124º 08.206'). One ♂ and one ♀ paratypes ( Field Museum of Natural History ) and another ♀ paratype ( NCSM) taken by same collectors on 13 February 2005 on Queets River Rd. ca. 5.8 mi (9.3 km) NE jct. US hwy. 101 (N 47° 39.34', W 124° 8.16'). These sites are in the southwestern corner of Jefferson County approximately 9.2 mi (14.7 km) ENE of the town of Queets .

Etymology. We are pleased to name this species for our colleague Bill Leonard, who has, by his assiduous collecting, more than doubled the number of milliped species known from the state of Washington.

Diagnosis. Ocelli 3 or 4 pairs; sternum of anterior gonopods elevated in midline, with two short lobes; anterior gonopod coxa without sclerotized flap, with flattened, medial extension; ultimate podomere complex, hirsute basally and narrowly rounded apically, with spiniform projections and a trapezoidal prolongation on anterior surface, and a quadrate flange on caudal margin.

Color in life ( Fig. 3). Dorsum generally light yellowish with mottled brownish patterns, tergites becoming progressively fainter and more indistinct caudad; collum and succeeding 3–4 tergites with strongest mottling but depigmented, without yellowish base color; venter pale.

Description. Body form normal for genus, long, narrow, and tapering at both ends, more strongly so on anterior end; dimensions of available specimens as follows: Holotype (36 segments including epiproct), 7.4 mm long (L), 1.4 mm wide (W), W/L ratio 18.9%; ♂ paratype (33 segs.), 6.0 mm L, 1.0 mm W, W/L ratio 16.7%; ♀ paratype (38 segs.), 9.5 mm L, 1.6 mm (W), W/L 16.8%; ♀ paratype (48 segs.), 15.8 mm L, 1.9 mm W, W/L 12.0%; juvenile paratype (29 segs,), 3.8 mm L, 0.9 mm W, W/L 23.7%.

Head subpyriform, smoothly continuing anterior tapering, labrum narrowly rounded. Ocelli darkly pigmented, either 3 pairs arranged linearly in slanted rows or 4 pairs with second ocellus (counting caudad from interantennal region) displaced slightly laterad. Antennae extending backwards to anterior margin of 5 th tergite, composed of seven articles, 2–5 clavate, relative lengths of antennomeres 6>5>3>4>2>1>7.

Midbody tergites normal for genus, with faint ozopores at caudolateral corners; epiproct rounded, protruding slightly caudad. Opposing legs separated by relatively broad sterna, legs extending laterad and terminating short of lateral segmental margins, invisible in dorsal perspective.

Sternum of anterior gonopods ( Figs. 4–5) elevated in midline and expanding into two short, subquadrate lobes. Anterior gonopod coxa with flattened medial extension, podomeres 2–4 with narrow, elongate, medial lobes; ultimate podomere elongate and complex, directed anteriad, hirsute basally and glabrous thereafter, hirsute basal part terminating in rounded shoulder proximal to quadrate flange on caudal surface, with three slender, spiniform projections on anterior margin opposite flange, middle one longest, podomere curving slightly laterad distally with narrowly rounded tip overhanging shallowly bifurcate, trapezoidal prolongation on anterior margin distal to spines. Posterior gonopod sternum ( Fig. 6) broad, expanding slightly laterad, ultimate gonopodal podomere strongly falcate with suggestion of subapical barbs (difficult to discern clearly even at 400x).

Ecology. The specimens were encountered in winter in leaf litter and under woody debris and rocks in second­growth rainforest approximately 40m south of the Queets River. The canopy was nearly closed and dominated by western hemlock ( Tsuga heterophyla ), western red­cedar ( Thuja plicata ), red alder ( Alnus rubra ), and sword fern ( Polystichum munitum ). Mr. Leonard's diplopod discoveries have generally come in winter or early spring ( Shelley, 2003 b; Shear & Leonard 2003, 2004), a time that past collectors avoided because of the inevitable cold, damp weather. Consequently, he has unearthed an entirely unknown fauna in this part of the continent.

Distribution. Known only from the type locality, which is approximately 180 mi (288 km) north of S. benedictae Shelley in Lincoln County, Oregon, and 90 mi (144 km) north of the Columbia River.

Remarks. Stenozonium leonardi exhibits the light yellowish coloration and long narrow body form of the congeneric species in Oregon and California, so these features truly diagnose the genus. However, the absence of the base color on the anteriormost segments in S. leonardi , photographed alive in fig. 2, is striking, and these segments also exhibit the heaviest mottling. Whether this depigmentation exists in S. exile and benedictae is unknown, as all the available material had been preserved in alcohol for at least 21 years when Shelley (1998) described them.

The W/L ratio drops noticeably with age, as the millipeds add segments and grow longer but do not become proportionally broader.

Stenozonium leonardi appears to be closely related to S. benedictae , the more proximate species, with which it shares a flattened, medially extended anterior gonopod coxa; the sclerotized coxal flap readily distinguishes S. exile from both of these species. The new species differs from S. benedictae in the shape of the sternal plates, which can be ascertained by comparing the figures in Shelley (1998) with ours. In proposing the genus and the two original species, Shelley (1998) did not closely examine the ultimate anterior gonopod podomeres for fine structure as we show in our figures of S. leonardi . His drawings ( Shelley 1998, figs. 22–25), done at high magnification under a compound microscope, do not reveal complexities necessitating closer examination, but now that such has been found in S. leonardi , the other species need to be re­examined in this regard.