Revision of the milliped genus Pleuroloma (Polydesmida: Xystodesmidae)

Abstract

The rhysodesmine xystodesmid milliped genus, Pleuroloma, is unique to the family in its great age, extensive range, high ecological adaptability, and aggregating and migrating behavior. Four species are recognized, two of which, P. pinicola, in coastal North and South Carolina, and P. plana, ranging from piedmont South Carolina to the Gulf Coast of north Florida, are described herein. Of the 12 nominal species in Pleuroloma today, 10 are synonyms of the type species, P. flavipes Rafinesque, which occurs from the eastern Atlantic Coast of the United States to the central Great Plains. The fourth species, P. cala (Chamberlin), occurs in peninsular Florida south of the Suwannee River. Specific differences in Pleuroloma are subtle, and characters useful in making determinations include segmental profile, configuration and degree of pubescence of the sterna, and aspects of the male gonopods. Identifications are most reliable when based on characters in combination. The tendency to aggregate in masses and migrate is important behavior for Pleuroloma, especially P. flavipes, and appears to at least partly explain its great range. The other three species appear to have arisen from two successful penetrations of the southeastern Coastal Plain by P. flavipes during the Pliocene and early Pleistocene. Generically Pleuroloma appears most closely related to Cherokia, but their distinctly different gonopods suggest an early dichotomy.