Pseudopolydesmus minor, MINOR (BOLLMAN, 1888)

Sierwald, Petra, Hennen, Derek A, Zahnle, Xavier J, Ware, Stephanie & Marek, Paul E, 2019, Taxonomic synthesis of the eastern North American millipede genus Pseudopolydesmus (Diplopoda: Polydesmida: Polydesmidae), utilizing high-detail ultraviolet fluorescence imaging, Zoological Journal of the Linnean Society 187 (1), pp. 117-142 : 135-136

PSEUDOPOLYDESMUS MINOR ( BOLLMAN, 1888)

( FIGS 21–25 )

Polydesmus minor Bollman, 1888: 2 , ♂ ST (USNM, non vidi, type lost). – Chamberlin, 1942b: 19, fig. 32.

Pseudopolydesmus minor – Chamberlin, 1943c: 18. – Chamberlin & Hoffman, 1958: 70. – Loomis, 1959: 161, fig. 9. – [ Withrow, 1988: 120, figs 62, 79, 97, 101, 105, 117, 119, 122–126, map 9, tables 9–11.] – Hoffman, 1999: 444.

Polydesmus neoterus Chamberlin, 1942b: 10 , figs 30, 31, ♂ HT (USNM, vidi), synon. nov.

Pseudopolydesmus neoterus – Chamberlin, 1943c: 18. – Chamberlin & Hoffman, 1958: 70.— Hoffman, 1999: 445.

Polydesmus euthetus Chamberlin, 1942b: 11 , fig. 36, two ♂ / ♀ ST (USNM, vidi), synon. nov.

Pseudopolydesmus euthetus – Chamberlin, 1943c: 18. – Chamberlin & Hoffman, 1958: 70.— Hoffman, 1999: 444.

Diagnosis

Size: Small, with body length ranging from 8.8 to 12.7 mm and an average body length of 10.5 mm (N = 31; Withrow, 1988: 124, 199). Comparable in size to Ps. caddo and Ps. paludicolus . Clearly smaller than all other congeneric species.

Paranota and tergal sculpture ( Figs 21 , 22 ): Corners of paranota forming a narrow parallelogram, with medial and lateral edges roughly twice as long as anterior and posterior edges. Anterior lateral and posterior lateral corners posterior to AMC and PMC, respectively, giving characteristic swept-back appearance. Leading and distal margins highly variable, ranging from moderately to weakly curved. Anterior lateral corners and denticles ranging from moderate to obliterated. Trailing margin concave, strongly curved. Anterior blister row as thick as MB and PB rows combined. Individual MBs and PBs subequal in area. Central paranotal blisters occupying two-thirds of paranotal breadth. Lateral blisters unusually distinct, extending anteriorly past all setiferous denticles, aligned with longitudinal axis.

Gonopod ( Figs 23–25 ): Gonocoxa ventral lobe with two gonocoxal plates stacked dorsoventrally ( Fig. 25A ). Telopodite uniformly curved. Pulvillus elongate, pointed, much closer to base of acropodite than terminus. Processes e1, e3 and m3 absent. Process e2 very small, lobe-like ( Fig. 25A ); e4 medium-sized, unusually prominent, basal to terminal bristles. Ectal surface also with large flange (possibly homologous to e3) between processes m2 and m4 ( Figs 23A , 24A , 25A ). Process m1 unusually large, subtriangular, proximal to pulvillus; m2 large, subtriangular, midway between base and terminus of acropodite; m4 small ( Figs 23B , 24B , 25B ).

Type notes

Polydesmus minor (♂ ST, USNM, non vidi, type lost): Bollman (1888) described an unspecified number of specimens from Little Rock, Pulaski Co., AR, USA . He made no mention of female specimens. No type specimens of Ps. minor were located in the USNM collection (Sierwald, November 2015).

Polydesmus neoterus (♂ HT and two ♂ PT, USNM, vidi): From New Orleans, LA, USA, collected 17 April 1936 by L. Hubricht . Type lot: contains two ♂ PT, ♂ HT with gonopods removed, distal extremities of one broken gonopod (without pulvillus). The gonopod remains do not allow unequivocal identification of the specimen. However, paranota shape and tergal sculpture is distinct from that in the types of Ps. caddo (= Ps. bidens ), the only small-bodied congener that occurs in Louisiana.

Polydesmus euthetus (one ♂ and one ♀ ST, USNM, vidi): From Buder Park , Fenton, St. Louis Co., MO, USA collected 15 March 1936 by L. Hubricht . Type lot contains ♂ ST erroneously labelled ‘HT’ with a single dissected gonopod and ♀ ST labelled ‘Lectoallotype’.

Distribution

Southern Arkansas northward through Missouri and Illinois to Lake Michigan. Most commonly collected near the Mississippi River and its tributaries.

Additional specimens examined

FMNH INS7107 * .

Figures

Figure 21. Pseudopolydesmus minor, metatergite and paranota of body ring 10. Holotype, Polydesmus euthetus (USNM, ultraviolet enhancement).

Figure 22. Pseudopolydesmus minor, metatergite and paranota of body ring 9. Paratype, Polydesmus neoterus type series, adult female (USNM, ultraviolet enhancement).

Figure 23. Gonopodof Pseudopolydesmus minor. Holotype, Polydesmus euthetus (USNM). A, right gonopod, ectal view. B, right gonopod, medial view.

Figure 24. Gonopodof Pseudopolydesmus minor. Holotype, Polydesmus euthetus (USNM, ultraviolet enhancement). A, right gonopod, ectal view. B, right gonopod, medial view.

Figure 25. Gonopod of Pseudopolydesmus minor (FMNH INS7107, scanning electron micrograph). A, right gonopod, ectal view. B, left gonopod, medial view (image mirrored to match right gonopod).