Stenozonium Shelley, 1998

Shelley, Rowland M. & Shear, William A., 2005, A new milliped of the genus Stenozonium Shelley 1998 from Washington State, U. S. A.: first record of the genus and family from North of the Columbia River (Polyzoniida: Polyzoniidae), Zootaxa 1017 (1017), pp. 25-32 : 27-28

Genus Stenozonium Shelley, 1998

Stenozonium Shelley, 1998:12 . Hoffman, 1999:32. Shelley, 2002:92.

Type species. Stenozonium exile Shelley, 1998 , by original designation.

Diagnosis. As presented by Shelley (1998).

Components. Three allopatric species are known; others may exist in moist coastal environments north of San Francisco Bay.

Distribution. Occupying widely segregated areas in the Coast Range of northern California, central Oregon, and the Olympic Peninsula of Washington; the Oregon species also ranges eastward onto the western slope of the Cascades (Fig. 2).

Remarks. While additional species of Stenozonium may yet be encountered and the ranges of the known ones will surely expand with additional samples, the lacunae between the three components will surely never be completely filled because of their sizes (180 & 235 mi (288 & 376 km )). We therefore suspect that Stenozonium truly consists of allopatric species, in contrast to the continuous distributions of species and populations in the other Pacific polyzoniid genera, excepting the Monterey County, California, population of Bdellozonium cerviculatum , and in contrast to the continuous pattern in the Pacific species of Octoglena ( Shelley 1995, 1998). Allopatry patterns are indicators of age, evidence that a taxon has existed long enough for extinctions to generate anatomical and geographical discontinuities and isolate populations and species from each other. That Stenozonium alone among west­Nearctic polyzoniidan genera exhibits allopatry suggests greater age and that it antedates the other genera. We cannot hypothesize time periods, but the geographic evidence suggests that Stenozonium is a product of an early dichotomy in the Polyzoniidae and that both Bdellozonium and Buzonium / Buzoniini are comparatively "young" taxa.