Semionellus
Chamberlin, 1920
Semionellus is a of flat-backed in the Xystodesmidae, established by Chamberlin in 1920. The genus contains at least three described : S. michiganus, S. placidus, and S. tertius. Members are found in the north-central and northeastern United States, including Michigan, Indiana, Ohio, Minnesota, and Maryland. As xystodesmid millipedes, they share the characteristic flattened body form typical of this diverse family of polydesmidan millipedes.
Pronunciation
How to pronounce Semionellus: /ˌsɛmiˈɔnɛləs/
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Identification
Distinguishing Semionellus from other xystodesmid requires examination of , particularly the structure of the male eighth leg pair modified for sperm transfer. Specific diagnostic characters for this genus relative to close relatives such as Nannaria or other Xystodesmini have not been summarized in readily accessible literature. -level identification within the genus relies on subtle differences in gonopod configuration and body counts.
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Distribution
Documented from Indiana, Michigan, Minnesota, Maryland, and Ohio in the United States. The appears restricted to the north-central and northeastern regions of the country.
Similar Taxa
- NannariaBoth are xystodesmid occurring in eastern North America with overlapping distributions; distinguished by and body proportions
- Xystodesmus of the Xystodesmidae; shares the flattened body plan but differs in structure and typically more extensive color pattern
More Details
Taxonomic history
Chamberlin established Semionellus in 1920, with S. placidus (originally described as Polydesmus placidus by Wood in 1864) later designated as a member. The has received limited modern taxonomic revision, and boundaries may warrant further study using molecular and morphological data.