Abacion wilhelminae, Shelley & Hollis, 2003

Shelley, Rowland M. & Hollis, Jennifer L., 2003, A new milliped of the genus Abacion Rafinesque, 1820 from Arkansas, U. S. A. (Callipodida: Abacionidae), Zootaxa 170 (1), pp. 1-7 : 3-6

Abacion wilhelminae , new species

Figs. 2­4

Type specimens. Male holotype (North Carolina State Museum of Natural Sciences collection [ NCSM]) collected by C. T. McAllister and J. L. Hollis on 21 March 2002 at the Pioneer Cemetery Historical Site along Arkansas highway 88 on Rich Mountain, ca. 1.5 mi (2.4 km) W Queen Wilhelmina State Park, Polk County, Arkansas. One male paratype ( NCSM) taken by C. T. McAllister on 11 June 2002 along Arkansas hwy. 272 on Rich Mountain , approximately 3 mi (4.8 km) E of Pioneer Cemetery; the other male paratype ( NCSM) taken by same collector on 9 November 2002 along the Ouachita Trail off highway 88 .

Diagnosis. A large­bodied species of Abacion characterized by the distally reflexed and narrowed, but apically broad, tibiotarsus, the broad lobe near midlength on the dorsal margin of the same, and the spiniform branch "A" of the postfemur, which diverges from branch "B."

Color in life. Dorsum dark mottled brown with narrow, inconspicuous, yellowish middorsal stripe running from 2nd to 59th segments, prozonites lighter than metazonites with light yellowish markings ventrolaterad through about segment 20, subuniformly dark brown with metazonites thereafter. Epicranium dark mottled brown, interantennal region lighter and remaining facial regions becoming progressively lighter through labrum. Antennae uniformly brownish, ultimate and penultimate articles lighter. Leg coloration subuniform with dorsum, ventral surfaces slightly lighter.

Holotype. Length about 44.6 mm, maximum width 2.5 mm, 62 segments.

Antennae long and slender, reaching back to caudal margin of 5th pleurotergite, 2nd and 4th­6th antennomeres clavate, 3rd long and slender, 1st broadly truncate, 7th sub­ rounded and narrowing apically, with four apical sensory cones; relative lengths of antennomeres 3>2=5>4>6>1>7. Ocellaria semilunar, rounded at bottom and sublinear at top, comprising ten angled rows with following numbers of ocelli: 4, 6, 8, 6, 6, 5, 4, 3, 2, 2.

Collum with twenty­six crests arising near midlength, medial ones slightly shorter, anterior half of collum smooth. Secondary carinae subequal in length to, but slightly lower than, primary ones, disappearing around segment 27; tertiary crests absent. Transition point from four to six primary dorsal crests (between poriferous carinae) on segment 12 as normal for genus; setal migration formula also normal for genus.

1st and 2nd legs short, incrassate, slightly more than half as long as subsequent legs. Legs 4­6 with spongy pads on distoventral extremities of tarsi; those on segments 3 through about 10 with comb rows of short, stiff setae on ventral surfaces of tarsi.

Gonopods ( Figs. 2­4 ) relatively small in overall size. Flagellum relatively broad for most of length, narrowing apically, extending to level of solenomere. Coxal process moderately long but terminating below distal elements, margins smooth, without flange. Femur with narrow, gently curved, medial lamina distal to flagellar crossing on caudal surface and small but distinct lobe distad on lateral margin. Distal elements angling sharply dorsad, at about a 45 o angle, from femur. Postfemur indistinct, fused basally with fold of tibiotarsus, solenomere arising dorsad at point of fusion, terminal branches arising slightly farther distad from common projection; branch "A" narrow and spiniform, diverging sharply from "B," angling subventrad and extending to level of outer margin of tibiotarsus; branch "B" broad and apically blunt, subequal in length to "A," dorsal margin gently curved, ventral margin sublinear; solenomere directed anteriad to branch "B" and overlain distally by latter in caudal view, gently curved and apically blunt, extending to level of distal extremity of "B." Tibiotarsus strongly reflexed, narrowed distad but not tapering, apically subbroadly rounded; with elevated ridge along midlength of inner surface, a broad, stubby, knob­like basal projection ventrad, a laminate ventral fold fusing with basal part of postfemur and extending into marginal lobe with minute teeth, and a broad, prolonged, lightly scalloped lobe on dorsal margin near midlength.

Male paratypes. Lengths ca. 46.4 mm, maximum widths 2.9 mm, 62 segments. Agreeing closely with the holotype in all particulars, the only discernable variation being a slight prolongation of the tip of the coxal process and a slightly smaller distal lobe on the lateral margin of the prefemur.

Ecology. The holotype was discovered under a decaying oak log in a deciduous forest at 2,900’ (870 m) along with a male of A. tesselatum , with which it is syntopic; two females that cannot be assigned to either species were also encountered under this log. One paratype was found in a spring seep under medium­sized rocks in a deciduous forest; two females of comparable size were also collected with this male, but it is unknown whether they are A. wilhelminae or A. tesselatum .

Distribution. Known only from the type and paratype localities ( Fig. 1 ). As A. wilhelminae has not been encountered elsewhere in Arkansas despite considerable collecting, we believe it may be endemic to the western periphery of the Ouachita Physiographic Province in Polk County and adjacent LeFlore County, Oklahoma, as are five species of salamanders ( Petranka 1998).

Etymology. The species name honors Queen Wilhelmina of The Netherlands (1880­ 1962), for whom the state park in Polk County is also named.

Remarks. Although females were collected along with the holotype and paratype, and at other sites in the western Ouachita Province, they are not characterized because it is unknown whether they belong to this species or to A. texense or A. tesselatum , which are sympatric on Rich Mountain, and the latter is also syntopic. Short of finding individuals in copula, we cannot accurately determine females of Abacion to species, and females of North American callipodidans in general have received little attention. Now that distributions are known based on males, it is possible to infer the identities of females in certain areas and learn their characters.

While the body colors of A. wilhelminae are as reported above, the milliped appears uniformly dark brown to the unaided eye. The middorsal stripe characteristic of abacionids is narrow and inconspicuous, detectable only under magnification.

The gonopods of A. wilhelminae are disproportionately small for so large an abacionid and are markedly smaller than those of A. lactarium , magnum , and tesselatum . As the tibiotarsus distal to the flexure is narrower than the proximal part of the structure, A. wilhelminae is distinguishable from A. magnum and A. lactarium , in which the breadth is subequal throughout. The subbroadly rounded tip contrasts A. wilhelminae with A. texense , which tapers smoothly and continuously to an acuminate tip. Abacion wilhelminae is also distinct from A. texense in the configurations and relative positions of branches "A" and "B" of the postfemur (compare figs. 2­4 herein with Shelley (1984, figs. 10­11)).

The discovery of A. wilhelminae at one locality in the midst of two widely distributed congeners is analogous to the occurrence of Delophon holti Shelley, 1979 at one site in Hamblen County, Tennessee, not far from known locales for the widespread species, D. georgianum Chamberlin, 1943 and D. serrulatum Causey, 1954 ( Shelley 1979) . Both A. wilhelminae and D. holti are anatomically disjunct to some degree and known only from one small area. Though not known yet from Tetracion Hoffman , the cavernicolous genus, the existence of both widely ranging and localized species is apparently a characteristic of the family Abacionidae in general.

Figures

FIGURE 1. Occurrences of species of Abacion in Arkansas. Dots, texense; squares, tesselatum; star, wilhelminae. As the three localities of A. wilhelminae are close together, they are indicated by a single star.

FIGURES 2­4. Abacion wilhelminae, holotype. 2, left gonopod, caudal view. 3, distal elements of the same, subventral view. 4, tibiotarsus, anterior view. "A," proximal branch of postfemur; "B," distal branch of postfemur; CP, coxal process; F, femur; FL, flagellum; PF, postfemur; S, solenomere; TT, tibiotarsus. Scale line = 0.4 mm for fig. 2, 0.5 mm for figs. 3­4.