GENUS PSEUDOPOLYDESMUS ATTEMS, 1898

(FIGS 1–8)

Pseudopolydesmus Attems, 1898: 270, 479. – Attems, 1914: 161. – Brölemann, 1916: 569. – Attems, 1926: 139. – Verhoeff, 1929: 619. – 1931: 305, figs 1–7. – Attems, 1940: 139, figs 201, 202. – Carl, 1941: 291, figs 1, 2. – Chamberlin, 1943c: 17. – Hoffman, 1950: 222, fig. 4. – 1974: 346 (= Dixidesmus). – [Withrow, 1988: 64.] – Hoffman, 1999: 442. – Djursvoll et al., 2000: 40.

Dixidesmus Chamberlin, 1943c: 18 . – Chamberlin & Hoffman, 1958: 65.

Type species: Polydesmus canadensis Newport, 1844 . By monotypy.

Diagnosis

Body form: Adult members of the genus Pseudopolydesmus always with 20 body rings including telson (never 19). Lateral corners of collum equal or exceed maximal width of mandibular stipites (narrower in Polydesmus and Brachydesmus, e.g. Djursvoll et al., 2000: 43, fig. 2a), except in Ps. paludicolus . Colour of adults in life ranging from dark brick red (Fig. 1A) to light chestnut brown (Fig. 1B).

Paranota and tergal sculpture: Paranota mostly level, extending horizontally (Fig. 2). Leading margin flexed anterodorsad, forming a narrow rim. Tergal sculpture pattern (described above; Fig. 4) very similar to other members of Polydesmidae, such as Po. inconstans and Po. complanatus, the latter of which is the type species of Polydesmus . Tergal blister pattern in Pseudopolydesmus less distinct than the strongly impressed pattern of Polydesmus . Unlike Po.inconstans and Po. complanatus, tergal setae not usually visible under dissecting microscope except in Ps. paludicolus, but may be visible with UV enhancement.

Gonopod: Gonocoxae large, with two long setae at the ventromedial margin. Posterior margin of gonocoxa divided into ventral and dorsal plate-like lobes that partly surround the telopodite basally. Ventral lobe with one or two gonocoxal plates stacked dorsoventrally. Telopodite falcate. Seminal canal originating medially before looping laterad, debouching at ectal base of pulvillus. Pulvillus entirely covered in bristles (Fig. 3). Seminal chamber large, with an associated duct (duct of the telopodite gland according to Verhoeff, 1931). Acropodite bearing between four and eight dentate to laminar processes along its ectal and medial surfaces; subterminally bearing from about ten to 60 terminal bristles (Fig. 5A, not socketed like true setae) similar in appearance to a toothbrush; terminally bifurcating into small ectal and medial processes or laminae too small to distinguish under dissecting microscope (Fig. 5B).

Somatic male characters: Prefemora of all walking legs beginning with leg pair 3 (body ring 4) strongly swollen dorsad in Pseudopolydesmus males (Fig. 6A), much more than in Polydesmus males (Fig. 6C). Male sterna with prominent paired lobes or tubercles of various shapes between leg pairs of body rings 5, 6, 7 and 8 (Fig. 7), which carry stiff, peg-like setae, differing from the unmodified setae of the walking legs. Leg pair 3 (body ring 4) with a pair of low lobes in some species; leg pairs 4 and 5 (body ring 5) with prominent lobes; leg pair 6 (anterior legs of body ring 6) with strongly elongated tubercles; leg pair 7 with small tuft of peg-like setae; leg pair 9 (directly posterior to gonopods) with tubercles flattened into longitudinal ridges (Fig. 8); leg pair 10 (anterior leg pair of body ring 8) with prominent ventrad-directed tubercles. This is unlike male Polydesmus, in which tubercles of leg pairs 9 and 10 (the first two leg pairs directly posterior of the gonopods) are absent or very slight. In some species (e.g. in Ps. erasus) there is an additional pair of lobes at the base of leg pair 11.

The species entries that form the remainder of the taxonomic section are presented in the order they appear in the above key to species. Each species name is given a comprehensive bibliography of published literature, including its junior synonyms and instances in which the name was misapplied. Notes are provided on the disposition of type material for each nominal species. Type abbreviations are as follows: HT, holotype; PT, paratype (s); ST, syntype (s). Names of states in the USA and provinces of Canada are shortened to their standard two-letter postal abbreviations. Specimen numbers of millipedes pictured in this paper that are not part of a type series are notated in bold with an asterisk, e.g. FMNH INS312685 *.

KEY TO SPECIES OF PSEUDOPOLYDESMUS MALES

1 a. Large recurved e2 process or fused recurved e2+e3 process ………………………………………………… 2 b. e2 notrecurved………………………………………………………………………………………………………4

2(1) a. Large recurved e2 not fused with e3 (Figs 10–12) …………………………………………………… Ps. erasus b. Fused e2+e3 process (Fig. 7) …………………………………………………………………………………… 3

3(2) a. m3 process distolaterad of m2; e1 elongate (Fig. 14) ………………………………………… Ps. canadensis b. m3 absent; e1 absent or severely reduced (Fig. 16) ……………………………………………… Ps. collinus

4(1) a. e3 large, spike-shaped; pulvillus large, rounded (Figs 18–20) ………………………………… Ps.pinetorum b. Ectal processes subtriangular or flanged; pulvillus pointed …………………………………………… … 5

5(4) a. Ectal surface strongly flanged, m4 process present ……………………………………………………………6 b. Ectal surface not flanged, with or without strongly flanged medial surface ………………………………7

6(5) a. Ectal flange smooth; large triangular m2 between flange and pulvillus (Figs 23–25) ………… Ps. minor b. Ectal flange bearing e3; no process between flange and pulvillus (Figs 27–28) ………………… Ps. caddo

7(5) a. Strongly flanged medial surface bearing m2 and m3 (Figs 30–31) ………………………… Ps. paludicolus b. Not flanged, with pronounced transverse ridge connecting e2 and m2 (Figs 8, 33) …………… Ps. serratus