The genus Karllangia Noodt, 1964, formerly included in the family Ameiridae, has been recently removed to Parastenheliidae Lang, 1944 (Willen, 2000). The genus presently shows a scattered distribution, suggesting a circumtropical-subtropical distribution but, as Mielke (1994) suggest, "any statement on its biogeography is surely premature".

* syn. Karllangia psammophila Wells, 1967 (Wells & Rao, 1987)

** incertae sedis according to Gee, 2006 [PDF]

*** questionable taxon

"The genus Rhizothrix Brady & Robertson, 1875 has a complex history. Brady & Robertson (1875) created the genus to accommodate R. curvata Brady & Robertson, 1875, the type species, but they did not include any description of the species. Later, Brady (1880) offered a detailed description of R. curvata. Pennak (1942) created the genus Adelopoda Pennak, 1942 and assigned it to the family Canthocamptidae Sars, 1906. Bodin (1997) was of the opinion that Adelopoda should have been assigned to the Cletodidae. Bozˇic´ (1953) considered Adelopoda a subgenus of Rhizothrix. Wells (1963) considered Adelopoda a synonym of Tryphoema Monard, 1926 and suggested that Tryphoema had to be considered a subgenus of Rhizothrix. Lang (1965) considered Rhizothrix and Tryphoema distinct, and reallocated the genus Adelopoda into the genus Tryphoema.

Por (1986) allocated the genera Rhizothrix and Tryphoema to the family Rhizothricidae Por, 1986. with other members of the genus. A key to

Currently, 12 species and subspecies are included within Rhizothrix. The type species of the genus, Rhizothrix curvata, was reported from British coasts.

Later, Scott (1903) reported R. minuta (T. Scott, 1903) and R. gracilis (T. Scott, 1903) from Scotland. Wilson (1932) described R. tenella (Wilson, 1932) from the Atlantic coast of North America, and Lang (1936) reported R. scotti (Lang, 1936) from the Arctic Ocean. Since Lang’s (1948) monograph, six species and subspecies have been added: R. reducta Noodt, 1952; R. reducta noodti Galhano, 1970; R. pubescens Por, 1959; R. quadriseta Wells, 1967; R. spinosa Coull, 1971; and R. wilsoni Bodin, 1979. Most recently, Arlt (1983) reported R. cf. minuta from the Baltic Sea and discussed the differences observed between his R. cf. minuta and R. minuta" (from: Nam & Le, 2005).