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Abstract
Rhoicosphenia is a relatively small genus with about 30 species and 30 infraspecific varieties. Over the past decade there has been a renewed interest in describing previously undocumented diversity in Europe, Asia and North America, from fossil and extant material, and from marine and freshwater environments. Of the ca. 60 Rhoicosphenia taxa, one species, R. lesothensis, has already been transferred out of the genus. During a literature review of the genus, a passage by Hustedt suggesting the need to transfer another species, R. vanheurckii, out of the genus was examined. Our morphological investigations result in the transfer of R. vanheurckii to the genus Planothidium. Although this diatom does not bear the cavum or sinus typical of most Planothidium species, it fits with the other characters of the genus and will retain the specific epithet, as P. vanheurckii (Grunow) E.W. Thomas, Van de Vijver & Kociolek comb. nov.
Acknowledgements
The authors would like to thank Dr. Marina Potapova of the Academy of Natural Sciences of Drexel University in Philadelphia for hosting EWT as a Jessup Awardee where the idea for this paper was conceived.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
Evan W. Thomas http://orcid.org/0000-0003-0432-3109