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Pandirodesmus rutherfordi, n. sp., represented by 18 individuals including eight adult males, occurs in secondary forests near Charlotteville and Speyside, Tobago, Trinidad and Tobago. Along with the type and second species, P. disparipes Silvestri, from Guyana and known only from females, the segmental legs of P. rutherfordi alternate between long (anterior pairs) and short (posterior ones), spiracular openings are on straw-like tubules, and ozopores are located on paramedian metatergal spines. These features appear to be adaptations for biotopes of loose sand, detritus, or frass, and 17 specimens, including the six juveniles, exhibit coatings of “sand grains” that are loosely cemented together and to the smooth, translucent, grayish-white exoskeleton. The tubules and spines elevate the spiracles and ozopores above the coating, thereby ensuring that they remain open and functional.
The coating, which provides camoufl age and lends strength and rigidity to the poorly sclerotized exoskeleton, is a subuniform “pavement” that covers the entire animal except the labrum/clypeus, tarsal and antennal apices, prozonae, paraprocts, and the gonopods in males. Ramose/dendritic setae, particularly on narrowly rounded podo-/antennomeres, trap “sand grains,” and the ozopore secretions apparently constitute the “glue” that cements the coating, as evidenced circumstantially by layers of “sand” between the spines on the anterior metaterga, where they are physically closest. The alternating segmental leg lengths, in part due to differing ventrolateral and ventromedial origins, appear to be an adaptation for lateral/sideways motion in which the long (anterior) legs extend laterally and pull the body to the level of the short (posterior) ones, which continue the motion while the anterior legs extend to begin the next stroke. The opposing legs perform the complementary pushing motion a fraction after the long legs initiate the pulling stroke and hence are slightly and purposefully out of sync. An adult male paratype lacks the coating, probably because it had just molted and lacked time to amass it; the juvenile female paratype of P. disparipes also is “naked,” as was, according to Silvestri, the now lost adult female holotype. Until fresh material is collected, coatings cannot be confi rmed for P. disparipes even though it shares the anatomical modifi cations that seem adaptions for such. The minute, triramous gonotelopodites of P. rutherfordi are unlike any known for a chelodesmid, so the current generic placement, in a monotypic tribe in the nominate chelodesmid subfamily, is retained. With species in both South America and the southern Antilles, Pandirodesmus/ini had to exist on both the “proto-Antillean” terrane and the adjoining part of Pangaean Gondwana before the former rifted in the Cretaceous/Paleocene, ~66 million years ago, and P. rutherfordi is a remnant of the former population that became isolated on present-day Tobago when the terrane fragmented. Affi nity between Guyanan and southern Antillean platyrhacid millipeds (Polydesmida: Leptodesmidea) suggest that Pandirodesmus/ini may occur sporadically as far north in the island chain as St. Lucia.
Tiphallus torreon n. sp., the fi rst rhachodesmid milliped from Coahuila, Mexico, displays an iridescent turquoise pigmentation with patterned white paranotal markings and a truncated, subapical projection from the broad, non-descript gonopodal acropodite. Four genera – Strongylodesmus Saussure, Mexidesmus Loomis, and Ceuthauxus and Tiphallus, both by Chamberlin – contain forms exhibiting this general condition, but the last is the only one whose type species does. Synthetic treatments are essential to advance familial knowledge beyond the descriptive stage, and revising these four taxa would constitute a meaningful initial study. Rhachodesmidae extend from northern Nuevo León, Mexico, ca. 77 km (48 mi) from the Rio Grande, to central Costa Rica; Glomeridae (Glomerida), Platydesmidae (Platydesmida), and Stemmiulidae (Stemmiulida) show similar distributions whereas Allopocockiidae (Spirobolida) and Rhysodesmus Cook (Polydesmida: Xystodesmidae) traverse the river and occupy southernmost Texas. Tridontomidae, the other component of Rhachodesmoidea, occupies a small enclave in Alta Verapaz, Guatemala. Rhachodesmidae/oidea do not occur in Panama and are initially recorded from Belize; localities are needed from Honduras.
Mimuloria Chamberlin 1928 is revived from synonymy under Nannaria Chamberlin 1918a for Nannariini (Polydesmida: Xystodesmidae) with simple but apically ornamented gonopodal acropodites that arch or lean mediad and cross body midlines and opposing acropodites in situ. It encompasses two assemblages based primarily on the nature of the ornamentations, the castanea and dilatata species groups. The former includes three established species [M. castanea (McNeill 1887) M. missouriensis Chamberlin 1928 and M. davidcauseyi (Causey 1950a)], and the latter contains two new ones (M. dilatata [M. d. dilatata, M. d. sigmoidea], and M.
rhysodesmoides). Castanaria Causey 1950b is returned to synonymy under Mimuloria, and C. depalmai Causey 1950b is placed under M. castanea, thereby constituting a new synonymy. The fi rst illustrations of the holotype gonopods of Fontaria oblonga C. L. Koch 1847 and N. minor Chamberlin 1918a unequivocally establish their identities, and the convoluted nomenclatural tangle involving Oenomaea Hoffman 1964 and O. pulchella (Bollman 1889a) is detailed. Whether in Oenomaea or a new genus, separate generic status seems appropriate for Nannariini with subterminal solenomeres; N. morrisoni Hoffman 1948 and its potential synonym N. shenandoa Hoffman 1949 may also belong here. Initial tribal localities are reported from Alabama, South Carolina, and coastal Virginia and Maryland, and “O. pulchella” occurs in northern Alabama north/west of the Tennessee River; M. castanea is newly recorded from Missouri and Tennessee. A horizontally subtriangular distribution in the eastern and midwestern states is projected for Nannariini, which even occur on South Bass Island, Ohio, in Lake Erie, and may thus inhabit
nearby Pelee Island, Ontario, Canada.