Expanded concept of the milliped family Spirobolidae (Diplopoda: Spirobolida: Spirobolidea): Proposals of Aztecolini n. tribe and Floridobolinae/ini and Tylobolini n. stats.; re)descriptions of Floridobolus and F. penneri, both Causey, 1957, and F. orini n. sp.; hypotheses on origins and affinities
Date of this Version
Insecta Mundi 0357: 1–50
The endemic Floridian milliped genus, Floridobolus Causey, 1957, more closely related to tylobolinines in the western United States (US), Mexico, and Guatemala than syntopic spirobolines, is incorporated into Spirobolidae (Spirobolida: Spirobolidea). With taxonomic priority by one year, its monotypic family is reduced to Floridobolinae, n. stat., comprising Floridobolini and Tylobolini, n. stats., the counterpart to Spirobolinae, comprising Spirobolini and Aztecolini, n. tribe; relationships are Floridobolini + (Tylobolini + (Aztecolini + Spirobolini)). Like F. penneri Causey, 1957, 208 km (130 mi) to the south in the Lake Wales Ridge, Polk and Highlands counties (cos.), F. orini n. sp., inhabits “Big Scrub” environments in the Ocala National Forest, Marion Co. Biogeographic reconstructions, compatible with broader hypotheses on the class’ evolutionary history, indicate that, from a presumptive source area in northern Mexico where the subfamilies overlap, spirobolid stock penetrated the “proto-US” four times, once per tribe, before the Western Interior Seaway developed in the Cretaceous Period, Mesozoic Era. Three expansions headed northeastward into future “Appalachia,” from which taxa spread southward as the Seaway receded. Floridobolini, the fi rst invader, had to be in “proto-Georgia” and positioned to penetrate Florida when the sand dunes that comprise the “Central Highlands” emerged from the sea in the Oligocene (Cenozoic), ~25 mya. As sea levels rose and fell, the dunes fragmented into islands and the subcontinuous Floridobolus population was partitioned. The southernmost became F. penneri; F. orini inhabited a northern island; and a graduate student is investigating other insular remnants for additional species. Shortly after Floridobolini began spreading, Hiltonius/ Tylobolini arose and expanded both southward to Guatemala and northwestward to California; Tylobolus Cook, 1904, diverged in the latter area and dispersed northward to Washington and eastward to Utah/Arizona. The third invader, and the second to disperse northeastward, was Aztecolini, which probably eradicated Floridobolini from some of its established range and was partitioned into Mexican (Aztecolus Chamberlin, 1943) and US (Chicobolus Chamberlin, 1947) taxa by the Seaway. The fi nal invader, Spirobolini, dispersed northwestward and northeastward to both the Pacifi c and Atlantic coasts; instead of Trans-Beringia, we prefer penetration of the Asian part of “Asiamerica,” when it temporarily formed during the Cretaceous, to explain the Mongolian fossil genus, Gobiulus Dzik, 1975, herein assigned to Tylobolini, and the occurrence of Spirobolus Brandt, 1833, in China and Taiwan today. In the east, Narceus Rafi nesque, 1820, spread across Appalachia, eradicated most remaining populations of Floridobolus and Chicobolus, and expanded to Maine and Québec after retreat of the Wisconsin glaciation. Chicobolus and Narceus also penetrated earliest Florida; the former established itself in the Central Highlands, spread through the widening peninsula as sea levels fell, and remained on insular refugia when waters rose. Apparently fueled by the different Floridian environments, Narceus underwent time-consuming speciation; consequently, Floridobolus and Chicobolus still survive on the peninsula, and an allopatric population of the latter inhabits coastal South Carolina. However, N. gordanus (Chamberlin, 1943) occurs syntopically with both in peninsular Florida and may be actively eradicating them from their last stronghold. Trigoniulus niger, takahasii, and segmentatus, all by Takakuwa, 1940, are removed from Spirobolidae and returned toTrigoniulidae (Trigoniulidea). New records in the Appendix include the fi rst of Aztecolus from Durango and Jalisco, Mexico.