The correct use of the names Synedra Ehrenberg and Catacombas Williams & Round, a note on the name ‘Hystrix Bory 1822’, and some suggestions how to tackle the taxonomic relationships of Synedra

Abstract

The genus name Synedra should now be used only for a group of marine species previously included in Catacombas, the latter name becoming a junior synonym. From a purely nomenclatural point of view, as numerous names remain in Synedra when they clearly do not belong there, a problem exists in how to treat those names. Two suggestions are made. One might explore existing names and their associated data; or one may treat the matter as a scientific problem, the problem of taxon relationships at various levels in the taxonomic hierarchy (genus, family, order, etc.), and explore the issue via systematic treatment of groups of species from the point of view of their monophyly. Monophyletic classifications at all ranks and supported by evidence (characters) allows a more scientific approach to understanding the relationships among various groups of species.

Keywords:

• Synedra
• Catacombas
• monophyly
• classification

Acknowledgements

A Synthesys. It is an EC research programme. award (EC-funded programme, 2017) to DMW made it possible to examine Bory’s diatom collections in the Muséum national d’Histoire naturelle, Paris. Ours thanks to Linda Medlin for guidance with the identification of Synedra koganii, Bart Van de Vijver for information on ‘Fragilaria’ famelica, Pat Kociolek for advice and comment, Eduardo Morales for clarifying his approach to the classification of these diatoms, two reviewers and Becky Bixby for numerous constructive comments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 For this date see below.

2 The proposal by Williams and Round was rejected without publication. The rejected manuscript can be made available on request.

3 The term aphyletic was proposed for situations when a few species sharing a newly proposed synapomorphy were removed from a larger named taxon. The group of species removed would be considered monophyletic, hence the latter, the residue, would become aphyletic, rather than paraphyletic, with their removal, as they would have no unique character(s) of their own (Ebach & Williams 2010, Williams & Ebach 2017).

4 The name Synedra helvetica was also used by Brutschy as the name preceding the Latin description. It might have been used in error, although rather confusingly, for the three illustrations the name Synedra cyclopum is used for Figures 11, 12a and 13, Synedra helvetica for Figure 12b. The name Synedra cyclopum is used in the final summary; ‘Neu ist Synedra cyclopum Brutschy als passiver Planktont auf den Cyclops-Arten’ (Brutschy 1922, p. 295).

5 There is also an entry for Ulnaria, which includes Synedra goulardii, its proper home (Williams & Karthick, unpubl.).

6 ‘It is not the intention of a cladistic analysis to recognize paraphyletic groups. However, since this study is done primarily at the generic level, genera that are not monophyletic may have groups of species assignable to other monophyletic groups, leaving the remainder as a paraphyletic assemblage at the most plesiomorph position of the more inclusive monophyletic group. In these cases, the traditional generic name will be retained, and recommendations for a species-level revision will be made’ (Parenti 1981, p. 346).

7 We leave aside the issue of ‘open nomenclature’, a set of procedures used mostly by palaeontologists and mostly applicable to questionable species identification (Bengtson 1988, Sigovini et al. 2016).

8 1986 was picked as a start date for this survey as this was the first time the genus was specifically defined by synapomorphies rather than simply described (Williams 1986).

9 This has been the result of nomenclatural decisions rather than taxonomic decisions (see Compère 2001 and Williams 2011).

10 But see Williams (Unpubl.) on Synedra curvata Østrup.

11 These numbers differ from those reported in Guiry & Guiry (2020) as we eliminated a few obvious duplications. By way of contrast, DiatomBase, which does not distinguish between accepted and rejected names, yields an astonishing 1272 names.

12 A later combination of Neodelphineis indica (F. J. R. Taylor) Hasle in Hasle & Syvertsen 1996, p. 309, figs 35–41, invalid

13 Synedra pelagica Hendey (1937, p. 335, pl. 17, fig. 11) was a new name for Synedra spathulata Schmiper non Synedra spathulata O’Meara.