Ptyoiulus Cook 1895

Shelley, Rowland M. & Smith, Jamie M., 2016, Parajulid milliped studies XII: Initial assessment of Ptyoiulus Cook 1895 and neotype designations for Julus impressus Say 1821 and J. montanus Cope 1869 (Diplopoda: Julida), Insecta Mundi 2016 (522), pp. 1-21 : 5-7

Genus Ptyoiulus Cook 1895

Ptyoiulus Cook 1895: 6 . Silvestri 1897: 650. Chamberlin 1940a: 15. Causey 1952a: 23. Chamberlin and Hoffman 1958: 141–142. Jeekel 1971: 174. Hoffman 1980: 108; 1999: 162. Shelley et al. 2000: 51. Shelley and Golovatch 2015: 4.

Type species. Julus (Julus) pensylvanicus (recte: pennsylvanicus ) Brandt 1841, by original designation. Gervais (1847, 1859) repeated the original spelling, but Wood (1865) and nearly all subsequent authors (see synonymies under Ptyoiulus impressus ) have employed the “two n” spelling. The earliest editions of the International Code of Zoological Nomenclature did not allow such corrections even for unequivocal misspellings; Pennsylvania, after all, is named for William Penn, with the two “n” spelling. However, the fourth edition of the Code, whose provisions took effect on 1 January 2000 and supersede those in previous editions, allows such corrections. Article 33.2.3.1 states “when an unjustified emendation is in prevailing usage and is attributed to the original author and date it is deemed to be a justified emendation,” and article 33.3.1 states “when an incorrect subsequent spelling is in prevailing usage and is attributed to the publication of the original spelling, the subsequent spelling and attribution are to be preserved and the spelling is deemed to be a correct original spelling.” Consequently, “ pennsylvanicus ” is now a justified emendation and the correct spelling for the specific name of the type-species ( Shelley and Golovatch 2015).

Descriptive notes. Adults long-bodied, upwards of 65 rings including collum and epiproct. Anterior rings lightly setose, gradually or abruptly becoming more setose and distinctly more so on caudal rings, epiproct, and paraprocts. Epiproct setose and spiniform, overhanging paraprocts and extending varying lengths beyond their caudal margins. Male first legs greatly enlarged, strongly forcipulate ( Blake 1931, fig. 2 in part), clearly more so than in other eastern family-group taxa. Telopodites of both pairs of gonopods lying entirely outside of aperture in situ, angling caudad over body and extending between leg pairs to level of rings 9–10. Anterior gonopod ( Fig. 5–6 ) comprising long, clavate, and distally hirsute telopodite and longer, glabrous coxal process terminating in laminate apical calyx, latter either slanting laterad, circumferentially entire, and marginally serrate or coaxial with stem of process, marginally smooth and cupulate on medial, lateral, and anterior surfaces (open caudad) ( Fig. 5–6 ); lateral syncoxal process absent. Posterior gonopod subacicular, inconspicuous, closely appressed to medial surface of stem of anterior gonopod coxal process, comprising two branches -- a long, slender major branch and shorter, spiniform, secondary branch arising at 1/4–1/3 of length of former; major branch curving basally then narrowing smoothly and continuously to scoop-like flange around 7/8 length, curving to acuminate tip distal to flange.

Distribution. The distributions of Ptyoiulinae and Ptyoiulus are the same, but we place our commentary with the genus because of doubts as to the merits of the subfamily. Past range descriptions include “Appalachian region from New York southward to Georgia, west to Illinois ” ( Chamberlin and Hoffman 1958), “centered in the Appalachian Mountains, extending north into southern Ontario, west to Arkansas, and south to Florida ” ( Causey 1974, for the redundant Ptyoiulini), and “Eastern North America” ( Hoffman 1999).

Ptyoiulus occupies five areas ( Fig. 4 , 14 ) -- a large one covering most of the US east of the Mississippi River, and four small, detached areas, two east and two west of this watercourse, one of the latter being a point locality. Overall, the known and projected generic range extends, north-south, from Montreal, Québec, to northern Florida and the Gulf Coast of the Panhandle; east-west, it spreads from Plymouth Co., Massachusetts, Currituck and Wilmington, North Carolina, Charleston, South Carolina, and Savannah, Georgia, to the southwestern shoreline of Lake Michigan, northeastern/eastcentral Arkansas, and the northeastern periphery of Louisiana. The known and projected range encompasses parts of two Canadian provinces, Ontario and Québec, and 27 US states and the District of Columbia , including all or essentially all of the following 16 listed from north to south: Rhode Island (projected), Connecticut, New Jersey, Pennsylvania, Ohio, Indiana, Delaware (projected), Maryland, West Virginia, Kentucky, Virginia, North Carolina, Tennessee, South Carolina, Georgia, and Alabama. The only states east of the Mississippi for which Ptyoiulus is neither known nor projected are Maine and New Hampshire; the only states west of the Mississippi where the genus either occurs or is projected are Missouri (projected for the “bootheel”), Arkansas, and Louisiana. Ptyoiulus is dominant in the southern Appalachian Mountains.

In Fig. 4 , the main area is number “1” and the detached ones are numbers 2–5. The first extends, north - south, from Boston, Massachusetts, Lake Ontario and the vicinities of Orillia, Ontario, and Flint, Michigan, to the Florida Panhandle; east - west, it extends from the Atlantic Ocean from Boston to Savannah to northwestern Indiana, the Mississippi River from southern Illinois to southern Tennessee, and 2/3 of the breadth of Mississippi. Maximal dimensions, both north/south and east/west, are around 1,508.0 km (942.5 mi). The detached areas are as follows:

(2). Montreal, Québec, to Franklin/Chittenden cos. in northern Vermont; length around 136.0 km (85.0 mi). We combine Montreal with the northernmost US sites for both the genus and P. impressus because the city is closer to them than to the nearest Canadian locality, Orillia, Ontario.

(3). Along the southwestern margin of Lake Michigan from Milwaukee, Wisconsin, to Lake Co., Illinois, north of Chicago, a distance of some 83.0 km (50.0 mi). We do not know how far inland this area extends.

(4). From the northeastern corner of Arkansas, and doubtlessly in the adjacent Missouri “bootheel,” to Cleburne Co., eastcentral Arkansas, a distance of 193.3 km (120.8 mi). The sites in Clay and Greene cos., adjacent to the “bootheel,” are in Crowley’s Ridge physiographic feature, which may have originated as an island between the Mississippi and Ohio Rivers that became a ridge of low hills on the west side of the former after their courses changed ( Shelley et al. 2012). Consequently, these populations of both species lie west of the Mississippi River and are detached from the rest of the generic range located east of the watercourse. The Cleburne Co. locality, the westernmost for the genus and P. impressus , is detached to the west-southwest and in the eastern Ozarks, suggesting more widespread occurrence in this region of the state.

5). A point locality in Morehouse Co., Louisiana, just south of the Arkansas state line, represented only by females. Latitudinally equivalent records in Mississippi, Alabama, Georgia, and Florida suggest that the species is P. impressus .

Remarks. In general, the species are anatomically stable with insignificant variation, the antithesis of Gosiulus conformatus Chamberlin 1940 (Gosiulini) , in which the gonopods of every male differ ( Shelley and Smith 2016). Such stability reflects age, and Ptyoiulus is clearly an old taxon that has occupied today’s North American land mass for a long time, perhaps since ancestral diplopods penetrated Euramerica after Baltica + Avalonia merged with Laurentia in the early Silurian Period, Paleozoic Era, 440 mya ( Shelley and Golovatch 2011). Gosiulus conformatus , however, is a young species that could not have arisen until after the Western Interior Seaway receded and the Texas lowlands became available for occupation. Insufficient time has passed since it arose for the gonopodal structure to stabilize.

The species of Ptyoiulus intermingle in the narrow east-west band of the generic range where P. montanus occurs ( Fig. 4 , red lines; 14). This distribution pattern suggests an old species, P. montanus , being displaced by the younger, more adaptable, and ecologically superior P. impressus . Sizeable populations of apparently pure P. montanus still exist, particularly in the central Carolinas and northeastern Mississippi, and both species seem to be abundant in the GSMNP and the Blue Ridge Mountains of southwestern North Carolina, where they tend to occur side-by-side. Otherwise, only small, isolated, and even point populations of P. montanus exist, some surrounded by primarily or exclusively P. impressus . The northernmost locality of the former is in Gallatin Co., Illinois, and a moderate-size population of the species occurs along the Ohio River in the southeast of this state. The northernmost population of P. montanus in the east is in Montgomery/ Giles Cos. , Virginia ( Fig. 14 ); P. impressus alone occurs from there northward, in formerly glaciated territory and in the following states with definite records plus the District of Columbia : Vermont, Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, Ohio, Indiana, Michigan, Wisconsin, Maryland, West Virginia, and Kentucky although records of P. montanus exist in Illinois and Tennessee that border Kentucky. Ptyoiulus impressus is also the only species in Florida and the southern halves of Georgia, Alabama, and Mississippi, which were inundated by the Western Interior Seaway in the late Cretaceous, approximately 60–80 mya. That impressus alone dispersed that far from refugia to the north testifies to its greater motility and adaptability. It is a substantially more successful species than P. montanus , whose populations are gradually dwindling and apparently relictual or nearly so in Virginia, Georgia, and Alabama.

Figures

Figure 4. Distributions of Ptyoiulus/Ptyoiulinae plotted against the maximal extent of the Western Interior Seaway during the Cretaceous Period, Mesozoic Era. All land areas shown are in the eastern land mass, Appalachia, which was separated from western Laramidia by the vertical, latitudinal arm of the Seaway (not shown), which segregated Ptyoiulus from bollmaniulinines in Laramidia but is irrelevant to Ptyoiulus itself. The Seaway spread eastward south of Appalachia and when it receded, P. impressus spread southward into the formerly inundated area. 1, large, contiguous main range area. 2, small, disjunct northernmost population extending from Montreal, Québec, to northern Vermont. 3, disjunct population along the southwestern coast of Lake Michigan. 4, disjunct area in northeastern/eastcentral Arkansas. 5, point locality in northeastern Louisiana vouchered by females. The transect denoted by the red lines near the center of the distribution is the band occupied by both P. montanus and P. impressus; the latter occurs alone to the north and south.

Figure 14. Distributions of species of Ptyoiulus. Black dots, P. impressus. Open black circle in southeastern Pennsylvania, denoted by the black arrow, is the neotype locality. Red dots, P. montanus. Open red circle in central North Carolina, denoted by the red arrow, is the neotype locality. Blue dots, geographically significant samples lacking adult males and presently unidentifiable to species.

Figures 5–6. Ptyoiulus spp. anterior gonopods, caudal views. 5) P. impressus. 6) P. montanus. at, anterior gonopod telopodite; ca, calyx; cp, coxal process stem.