Lumbriculus genitosetosus was described by Holmquist in 1976 from almost 2,000 individuals collected in Northern Alaska. Initially, Holmquist revived the genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Thinodrilus (previously established by Smith in 1895 for Th. inconstans) for L. genitosetosus, Lumbriculus inconstans and Lumbriculus ambiguus

Lumbriculus ambiguus

Lumbriculus ambiguus was described by Holmquist in 1976, based on material collected in northern Alaska. Like L. genitosetosus, L. ambiguus was initially placed in the genus Thinodrilus along with L. inconstans, but this genus is generally not recognised today...

on the basis of the Lumbriculus

Lumbriculus

Lumbriculus is a genus of oligochaetes....

-species having only one pair of vas deferens

Vas deferens

The vas deferens , also called ductus deferens, , is part of the male anatomy of many vertebrates; they transport sperm from the epididymis in anticipation of ejaculation....

 and sperm funnels per atrium, whereas the Thinodrilus-species have two (one in the anterior end and one in the posterior); this division is, however, not generally recognised today, even if Thinodrilus may be a valid subgenus.

L. genitosetosus, as the name suggests, can be recognised by its modified male genital setae, unique within the Lumbriculidae

Lumbriculidae

The Lumbriculidae are a family of microdrile oligochaetes common in fresh-water environments, including streams, lakes, marshes, wells and ground-water. They should not be confused with the earthworm family Lumbricidae. Many species and even genera are highly endemic, mainly in Siberia and the...

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