Pratherodesmus Shear

Shear, William A., Taylor, Steven J., Wynne, Judson & Krejca, Jean K., 2009, Cave millipeds of the United States. VIII. New genera and species of polydesmidan millipeds from caves in the southwestern United States (Diplopoda, Polydesmida, Macrosternodesmidae), Zootaxa 2151, pp. 47-65 : 50

Pratherodesmus Shear , new genus

Type species: Pratherodesmus voylesi Shear , new species.

Etymology: Named for the late John W. Prather, former lead scientist and spatial ecologist for the ForestERA Project, and professor at Northern Arizona University, Flagstaff, Arizona.

Diagnosis: Small (<10.0 mm length) polydesmidan millipeds with 20 trunk segments, lacking pigment; metatergites smooth, with three transverse rows of short, acute or clavate setae, rows sometimes strongly recurved. Collum ovoid, narrower than head and first leg-bearing segment. Paranota low, margins toothed, posteriolateral angles sharply drawn out. Pygidium blunt, nearly hemispherical when viewed dorsally, sparsely setose, with usual four spinnerets (Shear 2008) arranged in a square and set in individual depressions; pygidial process blunt, decurved. Males with pregonopodal legs unmodified or encrassate. Gonopods with coxae globular, fixed, entirely filling gonostome, tightly appressed or fused in midline; prefemora sparsely setose, strongly transverse, articulating with coxae by process fitting into coxal notch. Exomere small or absent, endomerite large, bulky, dominating gonopod. Acropodite short, solenomere nearly sessile, opening of seminal canal widened, subtended by cuticular teeth and two processes, one proximal and one distal (distal process=tibiotarsus?).

Pratherodesmus differs from Tidesmus Chamberlin 1943 ( Shear & Shelley 2007) in having a much smaller tibiotarsus of the male gonopod and in its smooth or nearly smooth metazonites. Sequoiadesmus Shear & Shelley 2008 occurs near the type locality of P. despaini , though at a much higher elevation and in a different cave group (see map in Shear & Shelley 2008); the gonopod of the single known species has an extremely long solenomere and lacks an exomere. Sequoiadesmus krejcae Shear & Shelley 2008 is also much smaller (5.8 mm long vs. 9.0 mm for P. despaini ) and has densely scattered, acute metzonital setae rather than short, clavate ones ranged in rows.

Distribution: Known from caves in northwestern Arizona and the Sierra Nevada of California.

Notes: The genus presently consists of three species of small, white, presumably troglobitic, millipeds found only in caves in the states of Arizona and California. We surmise that the species are in effect cavelimited (troglobionts), because the habitats surrounding the caves are inimical to small millipeds ( Fig. 38 ). The caves of the southwestern part of the United States have not been well-investigated for cave life, with the exception of limited studies of bats; and some investigations of caves where arthropods were opportunistically collected. Notable exceptions are cave-specific inventories of Carlsbad Caverns National Park, New Mexico ( Barr and Reddell 1967) and Karchner Caverns, Arizona ( Welbourn 1999). Broader surveys were published by Peck (1973, 1981, 1982). Given this, we expect more species of Pratherodesmus to be discovered in the future.

Figures

FIGURES 37, 38. Fig. 37. Living example of Nevadesmus ophimontis, photographed in Snake Creek Cave; length of animal is about 5 mm. Fig. 38. Great Basin pinyon-juniper woodland of the Snake Mountains seen from just inside the entrance to Snake Creek Cave (photos by J. Krejca).