A new milliped of the genus Metaxycheir from the Pacific coast of Canada (Polydesmida: Xystodesmidae), with remarks on the tribe Chonaphini and the western Canadian and Alaskan diplopod fauna

Abstract

Metaxycheir pacifica, a new chonaphine xystodesmid milliped from Vancouver Island, British Columbia, inhabits decidous spots in the forests along the Pacific Ocean from Bamfield to China Beach Provincial Park. It displays a subcylindrical body, imparted by reduced paranota caudal to segment 4; an acropodite in the form of a broad, open loop; and an acicular prefemoral process with minute subapical barbules. It is segregated from the type species, M. prolata Buckett and Gardner, in northern Idaho, by over 600 km, and is the second western Canadian xystodesmid. The tribe Chonaphini occupies five areas of allopatric populations: that of M. pacifica; from central Oregon to western Montana; and three areas in the north central and eastern states. The Pacific coastal region harbors the most diverse fauna of western Canada, and a second center of diversity lies around Mount Revelstoke and Glacier national parks. The diplopod fauna of Alaska and western Canada consists of at least 5 orders, 13 families, 22 genera, and 24 species; of these, 5, 10, 16, and 17 are indigenous forms and 2, 4, 6, and 7 are introductions, respectively. The chordeumatoid family Rhiscosomididae and the genus Rhiscosomides are new to Canada; five allochthonus species, Cylindroiulus caeruleocinctus (Wood), Ophyiulus pilosus (Newport), Oxidus gracilis (C. L. Koch), Brachydesmus superus Latzel, and Polydesmus inconstans Latzel, are new to the western provinces; and the Polyxenidae (Polyxenida) and Caseyidae (Chordeumatida) are new to Alaska.