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Research Article
The relationships of Eunotogramma frauenfeldii (Bacillariophyta) I. An account of its structure and description of the new genus Moralesonia
expand article infoDavid M. Williams‡, Tsvetoslav Georgiev‡, Tanja M. Schuster§, Carlos E. Wetzel|
‡ The Natural History Museum, London, United Kingdom
§ Museum of Natural History Vienna, Vienna, Austria
| Environmental Research and Innovation Department (ERIN), Institute of Science and Technology (LIST), Luxembourg, Luxembourg

Corresponding author: David M. Williams ( dmw@nhm.ac.uk )

Academic editor: Bart Van de Vijver
© 2024 David M. Williams, Tsvetoslav Georgiev, Tanja M. Schuster, Carlos E. Wetzel.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Williams D, Georgiev T, Schuster TM, Wetzel C (2024) The relationships of Eunotogramma frauenfeldii (Bacillariophyta) I. An account of its structure and description of the new genus Moralesonia. Plant Ecology and Evolution 157(3): 270-290. https://doi.org/10.5091/plecevo.121829
Open Access

Abstract

Background and aims – Euodia frauenfeldii has the characteristic ‘semi-circular’ or ‘crescent-shaped’ valves found in most species of Euodia, but as it also has a pair of conspicuous transapical costae, it was later transferred to Eunotogramma. Examination of the structure of its valves and girdle has led to a reassessment of its taxonomic position.

Material and methods – We discuss various aspects of terminology used for the parts of the valve, their abbreviations used throughout the literature and provide a detailed taxonomic background to both Euodia and Eunotogramma.

Key results – A new genus, Moralesonia is described and its relationships discussed.

Keywords

Bacillariophyta, Eduardo Morales (phycologist), Novara Expedition, synapomorphy

Introduction

The species first described and named as Euodia frauenfeldii Grunow (1863: 158, pl. 14, fig. 19, “Habitat ad litus Africae australioris (Flugsand der Kalkbay am Cap der guten Hoffnung, von Herrn v. Frauenfeld auf der Novara-Expedition gesammelt)”) possesses the characteristic ‘semi-circular’ or ‘crescent-shaped’ valves found in most species of Euodia J.W.Bailey ex Ralfs (in A. Pritchard 1861: 852), but also has a pair of conspicuous transapical costae (‘transapical ribs’). As a consequence, it was later transferred to Eunotogramma Weisse: Eunotogramma frauenfeldii (Grunow) Grunow (in Van Heurck 1883: pl. 126, fig. 14, “Golfe de Carpentaria, Pernambuco, etc.”).

Most of the species placed in Euodia since its first description, have been transferred to Hemidiscus G.C.Wall. (Wallich 1860: 42), primarily due to reasons of nomenclatural priority, as Euodia is a junior synonym of Hemidiscus. Euodia J.W.Bailey happens to also be a younger homonym of Euodia J.R.Forst. & G.Forst. (Forster and Forster 1776, Rutaceae) rendering the diatom name Euodia illegitimate for those two reasons.

Other species in Euodia were transferred to different genera, such as Flexibiddulphia Simonsen (= Euodiella P.A.Sims, see Williams and Sims 2022), Leudugeria Temp. ex Van Heurck, Cymatotheca Hendey, Eunotia Ehrenb., and Eunotogramma (see Table 1). In all, ca 12 species remain ‘unknown’ or ‘uncertain’ regarding their placement, making it clear that regardless of its convoluted nomenclature, the genus Euodia was an artificial assemblage to begin with (see also Table 1, ‘Current name’ column), whose species happened to simply share the possession of ‘crescent-shaped’ valves.

Table 1.
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Names of species placed in the genus Euodia J.W.Bailey ex Ralfs from 1861–1987) showing that this was an artificial assemblage composed of several species currently recognised as distinct; table excludes the varieties of Euodia gibba and those of other species. The column ‘Name’ refers to the original assigned to Euodia, followed by the column ‘Date’ when first described. The binomials given in the ‘Current name’ column are those currently accepted. The genus name Hemidiscus has been retained for Hemidiscus cuneiformis rather than Actinocyclus (after Gómez et al. 2017). Names in single quotes were invalidly published. Some notes on the names: Gómez et al. (2017: 26) considered Euodia barbadensis to be Hemidiscus barbadensis (Grev.) Kuntze, and a heterotypic synonym of Actinocyclus cuneiformis (G.C.Wall.) F.Gómez, Lu Wang & Senjie Lin. Greville’s figures (Greville 1861: pl. VIII, figs 6, 7) suggest otherwise, and Sims’s determination of Euodia barbadensis as a species of Medlinia seems more appropriate (Sims 2000: 406). Hustedt made all of Castracane’s species of Euodia taxonomic ‘forms’ of Hemidiscus cuneiformis (Hustedt in Schmidt 1940: pls 435–439), whereas Gómez et al. (2017: 26) made them all synonyms of Hemidiscus cuneiformis (see also Peragallo and Peragallo 1897). The identification of Euodia minima as Cymatotheca weissflogii follows Simonsen (1992: 19–20).

Name Date Current name [? = assumed] Publication
Euodia gibba J.W.Bailey ex Ralfs 1861 [Hemidiscus cuneiformis G.C.Wall.]
Hemidiscus cuneiformis [var. gibba (J.W.Bailey ex Ralfs) Hust.]		 Hustedt (1930)
Euodia barbadensis Grev. 1861 Medlinia P.A.Sims ? Greville (1861)
Euodia brightwellii Ralfs 1861 Euodiella semicircularis (Brightw.) P.A.Sims = Flexibiddulphia semicircularis (Brightw.) Simonsen Simonsen (1987)
Euodia frauenfeldii Grunow 1863 Eunotogramma frauenfeldii (Grunow) Grunow Grunow (1863)
Euodia chimmoana O’Meara 1869 Hemidiscus G.C.Wall. O’Meara (1869)
‘Euodia hardmaniana (Grev.) H.L.Smith’ 1877 Palmerina hardmaniana (Grev.) Hasle Smith (1877)
Euodia ceylanensis Leud.-Fortm. 1879 Hemidiscus G.C.Wall. ?? Actinocyclus Ehrenb. ?? Leuduger-Fortmorel (1879)
Euodia janischii Grunow 1883 Leudugeria janischii (Grunow) Temp. ex Van Heurck Van Heurck (1896)
Euodia weissflogii Grunow 1883 Cymatotheca weissflogii (Grunow) Hendey Hendey (1957) [1958]
Euodia producta Grunow 1883 Leudugeria Temp. ex Van Heurck ? Van Heurck (1896)
Euodia inornata Castrac. 1886 Hemidiscus cuneiformis G.C.Wall. Castracane (1886)
Euodia orbicularis Castrac. 1886 Hemidiscus cuneiformis G.C.Wall. Castracane (1886)
Euodia radiata Castrac. 1886 Hemidiscus cuneiformis G.C.Wall. Castracane (1886)
Euodia recta Castrac. 1886 Hemidiscus cuneiformis G.C.Wall. Castracane (1886)
Euodia ventricosa Castrac. 1886 Hemidiscus cuneiformis G.C.Wall. Castracane (1886)
Euodia striata Grove & Sturt 1887 Eunotia grovei Desikachary & Sreel. Grove and Sturt (1887)
Euodia atlantica Petit in Perag. 1888 Hemidiscus G.C.Wall. Peragallo (1888)
Euodia rotundus Janisch 1888 ? Janisch (1888)
Euodia margaritacea Brun in Brun & Tempère 1889 Hemidiscus cuneiformis G.C.Wall. Brun and Tempère (1889)
Euodia capillaris Brun 1891 Palmerina (Grev.) Hasle Brun (1891)
Euodia hungarica Pant. 1892 ? Pantocsek (1892)
Euodia cuneiformis (G.C.Wall.) A.Mann 1893 Hemidiscus cuneiformis G.C.Wall. Mann (1893)
Euodia ratabouli Brun in Leuduger-Fortmorel 1898 Cymatotheca weissflogii (Grunow) Hendey ? Leuduger-Fortmorel (1898)
Euodia arcuata B.Schröd. 1900 Hemidiscus G.C.Wall. ?? Actinocyclus Ehrenb. ?? Schröder (1900)
‘Euodia gigantea’ Brun 1907 Hemidiscus G.C.Wall. Tempère and Peragallo (1907)
Euodia subrotundata Azpeitia 1911 ? Azpeitia Moros (1911)
Euodia caballeroi Azpeitia 1911 ? Azpeitia Moros (1911)
Euodia minima Heiden & Kolbe 1928 Cymatotheca weissflogii (Grunow) Hendey ? Heiden and Kolbe (1928)
Euodia semicircularis (Brightw.) Hust. in A.Schmidt 1940 Euodiella semicircularis (Brightw.) P.A.Sims = Flexibiddulphia semicircularis (Brightw.) Simonsen Schmidt (1940)
Euodia udiensis Hust. ex Simonsen 1987 Flexibiddulphia udiensis (Hust. ex Simonsen) Simonsen Simonsen (1987)

The genus Eunotogramma (Weisse 1855a [1854], 1855b) is similar, inasmuch as most of its included species (ca 40 names) have been dispersed to other, more appropriate genera based on morphological studies (Table 5, see ‘Current name’ column). It too is now being recognised as an artificial assemblage of species, which happen to have conspicuous transapical costae (‘transapical ribs’, see below) on the valves.

In this study, we have examined a number of herbarium specimens that have been named Euodia frauenfeldii, including relevant type specimens using LM and SEM. To provide context, as a prelude to a cladistic analysis of the relevant characters that will follow elsewhere, and to demonstrate that Euodia frauenfeldii is neither a species of Euodia nor a species of Eunotogramma, we outline the taxonomic histories of both genera and document the structure of the valves and girdle of E. frauenfeldii. Based on these observations including a putative synapomorphy, we propose a new genus to accommodate E. frauenfeldii, describe one new species, and suggest others that might be described and included in due course.

Material and methods

Terminology

For the most part, the two standard valve and girdle terminology papers have been followed (Anonymous 1975 and its updated version Ross et al. 1979). Additional commentary can be found in Gogorev et al. (2018) and the glossaries in Diatoms of North America (see Spaulding et al. 2022) and Diatom Flora of Britain and Ireland (Jüttner et al. 2022). In many cases, there is no general agreement on the naming of particular valve and girdle parts. In these cases, we have either stated our source or if it is unique to us. In addition, problems with terminology can arise when the same term (name) is used for characters that are demonstrably non-homologous. For example, as Witkowski et al. (2020: 19) recently noted: “The presence of internal transverse costae across the ‘pennate/non-pennate’ diatom categories is hardly surprising, as it is part of a long list of ultrastructural features found in both generalized morphotypes along with apical pore fields, rimoportulae and marginal ridges”. Passing over what “generalized morphotypes” could mean, adopting a particular name for a feature without cladistic analyses does not (necessarily) imply it is homologous across all taxa that bear this character, nor should it be interpreted as such. To try and achieve some clarity, in this paper, we refer to the ‘internal transverse costae’ as ‘transapical ribs’. Nevertheless, our discussion of characters below is made with respect to proposing putative homologues, not simply to achieve terminological consistency, although both are obviously desirable. Most of that discussion will appear later in the companion paper (part II).

Abbreviations

LM = light microscope; SEM = scanning electron microscope; herbarium acronyms are according to Index Herbariorum (Thiers 2024). The exclamation point (!) following material citation means ‘vidi’ (‘We have seen it’). No abbreviations are used for valve and girdle structures.

Taxonomic background

We provide a reasonably detailed but succinct background (i.e. without swamping the text with every historical detail) for both Euodia and Eunotogramma with the aim of presenting evidence that they are artificial assemblages of unrelated taxa (i.e. polyphyletic).

Euodia J.W.Bailey ex Ralfs

The name Euodia was first used for a diatom genus by Ralfs in Pritchard’s History of the Infusoria, it being attributed to J.W. Bailey, as was the only definitely included species, Euodia gibba J.W.Bailey ex Ralfs (Ralfs in Pritchard 1861: 852, “Recent. Gulf Stream”). Ralfs provided a relatively simple description of the genus: “Frustules cellulose or granulate; in lateral view lunate. Euodia agrees with the Eunotieae in the shape of its frustules which can scarcely be called angular; yet, notwithstanding that resemblance in form, its punctate or granulate surface induces us to place it here”. Alongside E. gibba – which was based on “a drawing by Professor Bailey” (Ralfs in Pritchard 1861: 852, pl. viii, fig. 22, see our Fig. 1A) – Ralfs included Euodia brightwellii, albeit with some reluctance (“E? Brightwellii”), suggesting it was a synonym of Triceratium semicirculare Brightw. (Brightwell 1853: 252, pl. IV, fig. 21, “Bermuda Earth”, see our Fig. 1B) and, possibly, of Triceratium obtusum Ehrenb. (Ehrenberg 1844: 88 [1841: 329, “Virginien, Richmond”]; in Ehrenberg 1854: pl. XVIII, figs 48, 49, see Fig. 1C, D). Under his description of Hemisdiscus, Ralfs added: “We doubt whether Hemidiscus be distinct from Euodia, since the only distinction seems to be the marginal nodule of the former, - a character perhaps overlooked by Professor Bailey” (Ralfs in Pritchard 1861: 852–853).

Figure 1. 

A. Euodia gibba, reproduced from Pritchard (1861: pl. viii, fig. 22), based on “a drawing by Professor Bailey” (Ralfs in Pritchard 1861: 852). B. Euodia brightwellii reproduced from Brightwell (1853: pl. IV, fig. 21, “Bermuda Earth”). C–D. Triceratium obtusum reproduced from Ehrenberg (1854: pl. XVIII, figs 48, 49, “Virginien, Richmond”). E. Eunotogramma Weisse figure reproduced from Weisse (1855a [1854]: pl. III [‘Dritte Tafel’], fig. 37a–e [f–i, k, l] – the latter few figures are not mentioned in Weisses’s legend’s title but f–h are noted in the text; i, k, l are referred to as “Die übrigen [the remainder]”, Weisse 1855a [1854]: 278).

The complex history of the name Euodia has been tackled a number of times (e.g. Hendey 1957 [1958]: 32; Simonsen 1987: 263; Sims 2000; Blanco and Wetzel 2016: 195–196; Gómez et al. 2017). It can be briefly summarised thus: after Ralfs’ initial account in Pritchard, a number of other species were added, all more or less with the ‘lunate’ valve outline (Table 1).

Hustedt transferred Euodia gibba, the generitype, to Hemidiscus under the name H. cuneiformis var. gibba Hust. (Hustedt 1930: 906, fig. 542g; see also Peragallo and Peragallo 1897) and later proposed a change of rank to H. cuneiformis f. gibba Hust. (Hustedt 1940: pl. 435, figs 4–6).

More recently, Gómez et al. (2017: 26) suggested that, using molecular evidence, “[…] H. cuneiformis should be transferred to Actinocyclus Ehrenb. If Hemidiscus is retained as an independent genus, the current placement of Hemidiscus in the SSU rDNA phylogenetic tree makes Actinocyclus paraphyletic. Thus, either Hemidiscus is part of Actinocyclus, or Actinocyclus should be broken up into different genera” – this deserves comment, which is presented elsewhere (Williams in press).

It is worth noting that Ehrenberg’s name Dichomenis Ehrenb. (Ehrenberg 1862: 293; see also Ehrenberg 1873: 264–265) is another junior synonym of Hemidiscus. Only three species were ever transferred to Dichomenis alongside Ehrenberg’s D. subtilis Ehrenb., and all are now in Hemidiscus with the exception of D. janischii (Grunow) Karst., which is Leudugeria janischii (Grunow) Temp. ex Van Heurck (Table 2). Ehrenberg’s D. subtilis may have nomenclatural significance for species in Hemidiscus.

Table 2.
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Names placed in Dichomenis Ehrenb.

Name Date Current name [? = assumed] Publication
Dichomenis subtilis Ehrenb. 1862 Hemidiscus cuneiformis G.C.Wall. ? Ehrenberg (1862)
Dichomenis cuneiformis (G.C.Wall.) Karst. 1928 Hemidiscus cuneiformis G.C.Wall. Karsten (1928)
Dichomenis janischii (Grunow) Karst. 1928 Leudugeria janischii (Grunow) Temp. ex Van Heurck Karsten (1928)
Dichomenis ventricosa (Castrac.) Skvortzov 1932 Hemidiscus cuneiformis G.C.Wall. Skvortzov (1932)

In summary, of the 30+ names in Euodia (Table 1), most are now in Hemidiscus, others are in Flexibiddulphia, Cymatotheca, Leudugeria, or Eunotia Ehrenb., with ca 12 with relationships either ‘unknown’ or ‘uncertain’; Euodia frauenfeldii is of uncertain relationships, but is currently included in Eunotogramma.

Eunotogramma Weisse

Weisse (1855a [1854], 1855b) offered the first description of the genus in the text of a detailed figure legend for the illustrations on his plate III (“Dritte Tafel”), fig. 37a–e [f–i, k, l] (the latter few figures are not mentioned in the legend’s title but f–h are noted in the text; i, k, l are referred to as “Die übrigen” [the remainder], and j is missing; Weisse 1855a [1854]: 278, 1855b: 244, see our Fig. 1E and Table 3). Weisse provided a possible choice of names for the different ‘kinds’ he illustrated: “Will man aus den verschiedenen Formen besondere Abarten bilden, so wären die Beinamen tri-quinque-septem und novem loculata wohl die passendsten” [If one wanted to rank these forms as species, the epithets tri-quinque-septem and novem loculata would likely be the most appropriate] (Weisse 1855a [1854]: 278, 1855b: 244; Ralfs (in Pritchard 1861: 860) appears to accept all of these names).

Table 3.
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Names of taxa in Eunotogramma according to Ehrenberg (1856: 103, 1876: 48–51; in brackets: ‘proper’ names, see Ehrenberg 1855: 298–299); the names are partly derived from his interpretation of Weisse’s taxa (1855a [1854], 1855b). References to Weisse’s plate III are shown in the second column (see our Fig. 1E; where the figures have been re-arranged to correspond to the taxon listing below, so that drawings referring to the same ‘species’ are placed together and in a series for direct comparison). Some notes on the names: Ehrenberg implied that E. weissei is a new species (“[Eunotogramma] Weiſsei n.sp.”, Ehrenberg 1855: 302), but earlier in the same paper he has it as a synonym of Biddulphia tridentata (Ehrenberg 1855: 298) as, later, does Grunow (1884: 59). There is a complex synonymy yet to be disentangled around the name Biddulphia tridentata.

Names in Ehrenberg Reference to Weisse’s plate III
3loculatum (Eunotogramma triloculatum Weisse) Taf. III, fig. 37a, e
5loculatum (Eunotogramma quinqueloculatum Weisse) Taf. III, fig. 37b, f, i, k
7loculatum (Eunotogramma septemloculatum Weisse) Taf. III, fig. 37c, g
9loculatum (Eunotogramma novemloculatum Weisse) Taf. III, fig. 37d, h, l
[β [var.] octonum] [Ehrenberg 1855: 302]
amphioxys n. Taf. III, fig. 36a–d [= Biddulphia tridentata Ehrenb.]
elongatum n. Taf. III, fig. 21 [= ?]
Weissei n. Taf. I, fig. 22a, b [= Triceratium Ehrenb. ?] [Ehrenberg 1855: 299]

Ehrenberg’s (1855: 302) own study of Weisse’s material accounted for eight taxa in Eunotogramma: E. novemloculatum Weisse, E. quinqueloculatum Weisse, E. septemloculatum Weisse, and E. triloculatum Weisse plus four new taxa provided by Ehrenberg: E. amphioxys Ehrenb., E. elongatum Ehrenb., E. septemloculatum β [var.] octonum Ehrenb., and E. weissei Ehrenb. In 1856, this work was summarised again with a list of species names including those in Eunotogramma (Table 3 modified from Ehrenberg 1856: 103; also in Ehrenberg 1876: 48–51).

Ehrenberg published no illustrations for any of his new taxa (nor do any exist in his unpublished drawings as far as we are aware), but his references to Weisse indicate what he had in mind for each (summarised in Table 3). It is still not clear if any of these names have been validly published, by Weisse, Ehrenberg, or anyone else, for that matter.

Subsequently, however, Grunow (in Van Heurck 1883) published a further six names in Eunotogramma: E. producta Grunow, E. laevis Grunow, E. variabilis var. quinqueloculare Grunow, E. variabilis var. septemloculare Grunow, E. frauenfeldii Grunow, and the questionable “E? debilis” Grunow (Table 4). Eunotogramma producta and these two varieties of E. variabilis were recorded from fossil material, “Dépôt de Simbirsk, Siberie”, the same locality as Weisse’s earlier study.

Table 4.
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The six names of Eunotogramma according to Grunow (in Van Heurck 1883); the first three (producta, laevis and debilis) are new to Grunow, the two varieties of variabilis, although derived from Weisse’s taxa, are nomenclatural status changes made by Grunow, where he attributed the original name to Ehrenberg rather than Weisse. Finally, Eunotogramma frauenfeldii is derived from Euodia frauenfeldii Grunow. Eunotogramma producta and E. variabilis (and its varieties) are all from “Dépôt de Simbirsk, Sibérie”, the same locality as Weisse’s taxa (found in W0164932: Grunow sample 3090).

Names by Grunow (in Van Heurck 1883) Locality
Eunotogramma producta “Dépôt de Simbirsk, Siberie”
Eunotogramma laevis “Caroline du Nord, Floride […]”
E.[unotogramma]? debilis “Baie de Campèche […] de I’lle Bartolomée […] d’Ostende (Belgique)”
Eunotogramma variabilis var. septemloculare “Dépôt de Simbirsk”
Eunotogramma variabilis var. quinqueloculare “Dépôt de Simbirsk”
Eunotogramma frauenfeldii (= Euodia frauenfeldii) “Golfe de Carpentaria, Pernambuco, etc.”

Witt (1885: 24, 1886: 160) recognised only E. variabilis and E. weissei.

No generitype was designated for the genus Eunotogramma until Boyer (1927: 143) chose E. triloculatum Weisse, which may still be unacceptable as it has yet to be validly described. Round subsequently designated Eunotogramma laevis Grunow as such, but, that too may be inappropriate as it is not associated with any material from the original publication (in Round et al. 1990: 288).

Table 5 is a selected list of taxon names in the genus Eunotogramma (from its creation in 1855 to the most recent addition in Witkowski et al. 2020; as in Table 1, for brevity’s sake, varieties have been omitted – but there are probably no more than four). Overall, there are roughly three groups: a distinct set of robust fossils, a distinct set of species that (probably) belong in Drepanotheca (Williams et al. in prep.; distinctions within Eunotogramma have previously been recognised by Sims 2000 and Witkowski et al. 2020: 21; a review of these species is in preparation), and a group of species ‘similar’ to Eunotogramma laevis, the generitype according to Round et al. (1990: 288; see Amspoker 2011, 2016), leaving only two species not fitting these broader categories: Eunotogramma rectum Salah (1955: 88) and, as in Euodia, Eunotogramma frauenfeldii.

Table 5.
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Selected list of names currently in, or that have been in, Eunotogramma; there are, roughly, three groups: *Fossil = a distinct fossil group of species, *Eunotogramma = those species ‘similar’ to Eunotogramma laevis (‘laeve’) (the generitype according to Round et al. 1990: 288, see Amspoker 2011, also Amspoker 2016), and species in Drepanotheca H.-J.Schrad. ex Crawford, Round & D.G.Mann; many species named by Ehrenberg were never illustrated and their interpretation relies upon his comparisons with Weisse (Table 3), most here being interpreted as ‘*Fossil’ (these will be dealt with in a subsequent contribution). Species names in single quotes are invalidly published. Some notes on the names: Boyer (1900: 737) noted that E. amphioxys is “equivalent to Biddulphia ? lunata E. […]”. An illustration of Biddulphia lunata can be found in Ehrenberg (1844: 77, 1854: pl. XVIII, fig. 53, “Richmond”, see also Ehrenberg 1855: 302). ‘Eunotogramma bicornigerum’ is given in Chambers (1997, nom. inval.). The illustrations in Simonsen suggest that Eunotogramma dubium may be a species of Ceratanaulus Górecka et al. (Simonsen 1987: pl. 374, figs 1–6). ‘Eunotogramma vittatum De Toni (1894: 892)’ is an error for Eunotogramma bivittata. De Toni refers to “Grun. et Pant. Foss. Bacill. Ung. I, p. 48, t. XXVI, f. 247”, which is the original description and figure of Eunotogramma bivittata (Pantocsek 1886: 48), and to “Grove & St. J.Q.M.C. 1887, p. 77, t. 6, 24”, which is a drawing of ‘Eunotogramma ? ? bivittata’ (Grove and Sturt 1887). De Toni notes the name ‘Anaulus tenuis’, an invalidly published name of Grove and Sturt (1887), which they refer to in their account of Eunotogramma ? ? bivittata. There are two Grove slides in BM with specimens labelled ‘Anaulus tenuis’. Both are specimens of Eunotogramma bivittata (BM Adams G80 and BM Adams G111, “Oamaru”; Mills’s notebook for Grove’s slides has ‘Anaulus tenuis Gr.’ and also refers to ‘Eunotogramma rigida’, another unpublished name, from “Oamaru”).

Species Current name or group (*Fossil/*Eunotogramma/Drepanotheca)
Eunotogramma amphioxys Ehrenb. ? ‘*Fossil’
‘Eunotogramma bicornigerum’ Flexibiddulphia Simonsen
Eunotogramma bivittata Grunow & Pant. Drepanotheca bivittata (Grunow & Pant.) H.-J.Schrad.
Eunotogramma cretacea Streln. ‘*Fossil’
Eunotogramma debile Grunow Anaulus debilis (Grunow) Van Heurck
Eunotogramma dubium Hust. ? Ceratanaulus Górecka et al.
Eunotogramma elongatum Ehrenb. ? ‘*Fossil’
Eunotogramma enorme Krotov ‘*Fossil’
Eunotogramma frauenfeldii (Grunow) Grunow This study (see taxonomic section below)
Eunotogramma fueloepi Hajós ‘Drepanotheca’
Eunotogramma fugei Chenev. ‘*Fossil’
Eunotogramma gibbosa Streln. ‘*Fossil’
Eunotogramma laevis Grunow *Eunotogramma
Eunotogramma lunatum Ashworth *Eunotogramma
Eunotogramma marginopunctatum J.A.Long, Fuge & Js.Smith ‘Drepanotheca’
Eunotogramma marinum (W.Sm.) Grunow Smithiella marina (W.Smith) H.Perag. & Perag. [*Eunotogramma]
Eunotogramma novemloculata Weisse ‘*Fossil’
Eunotogramma polymorpha Streln. ‘*Fossil’
Eunotogramma productum Grunow ‘*Fossil’
Eunotogramma quinqueloculatum Weisse ‘*Fossil’
Eunotogramma rectum Salah ?
Eunotogramma rostratum Hust. *Eunotogramma
Eunotogramma trioculata Weisse ‘*Fossil’
Eunotogramma variabilis (Ehrenb.) Grunow ‘*Fossil’
‘Eunotogramma vittatum’ ‘Drepanotheca’
Eunotogramma weissei Ehrenb. ‘*Fossil’

With respect to both Euodia and Eunotogramma, Eunotogramma frauenfeldii belongs in neither, as both genera are not defined with respect to any unique character of their own. Eunotogramma frauenfeldii has a central area with radiating areolae (a putative generic synapomorphy), and hence a new genus is proposed for it (Eunotogramma rectum will be investigated in due course). In addition, this is also based on a cladistic analysis, which will be published separately. The relationships of E. frauenfeldii, in comparison to the other relevant genera where former species of Euodia and Eunotogramma are now placed, will be discussed in detail.

Taxonomic treatment

Moralesonia D.M.Williams, Ts.Georgiev, T.M.Schust. & C.E.Wetzel, gen. nov.

Type species

Moralesonia frauenfeldii (Grunow) D.M.Williams, Ts.Georgiev, T.M.Schust. & C.E.Wetzel, comb. nov.

Etymology

Named for the late Eduardo Morales (1968–2023, https://diatoms.org/news/in-memoriam-eduardo-a-morales).

Registration

http://phycobank.org/104544

Description

Valves lunate, each with two transapical ribs dividing valve into three ± equal parts. Transapical ribs evident, extending to mantle, internally raised, tapering towards mantle edge. Areolae ± round, radiating from eccentric hyaline centre, sometimes elongated. Rimoportulae absent. Few simple pores on valve surface. Cribra with well-developed, complex volate structure. External surface of valve ornamented. Girdle composed of few bands, all (presumed) copulae. ‘Central area with radiating areolae’ is the proposed (putative) synapomorphy (diagnostic character) for this genus.

Notes

We have included all specimens from various parts of the African continent in Moralesonia frauenfeldii and omitted those from other localities for the time being, except from two samples from the Nicobar Islands as they present a similar morphology. These specimens may not be Moralesonia frauenfeldii but, as yet, detailed examination has not been possible (see below). Of these, we have documented them according to the details available to us. The specimens from Australia have been given a specific name, while the others are left without names as relevant characters have yet to be identified. We have SEM details for some specimens from Île Rodriguez, but no LM specimen, so are unable to assign a holotype other than the SEM stub, which we are reluctant to do at this time as their longevity cannot be established with any certainty (Fig. 10A–F).

Moralesonia frauenfeldii (Grunow) D.M.Williams, Ts.Georgiev, T.M.Schust. & C.E.Wetzel, comb. nov.

Figs 2, 3, 4, 5, 6

Euodia frauenfeldii Grunow (basionym), Verhandlungen der Kaiserlich-Königlichen Zoologisch-Botanischen Gesellschaft in Wien 13: 158, pl. 14, fig. 19a–d (= our Fig. 2A) (Grunow 1863). Also described in Grunow (1864: 119) and Grunow (1878: 24).

Eunotogramma frauenfeldii (Grunow) Grunow (in Van Heurck 1883: pl. 126, fig. 14, reproduced here as Fig. 4J–K).

Type locality

South Africa, Kalk Bay [Kalkbaai] (“Habitat ad litus Africae australioris [occurs on the South African coast] (Flugsand der Kalkbay am Cap der guten Hoffnung, von Herrn v. Frauenfeld auf der Novara-Expedition gesammelt [airborne sand from Kalkbay at the Cape of Good Hope, collected by Mr. von Frauenfeld during the Novara Expedition])”), (Grunow 1863: 158; “Im Flugsande der Kalkbai am Cap der guten Hoffnung, Frauenfeld [in airborne sand from Kalkbaai at the Cape of Good Hope, Frauenfeld].” “Auch im Strandsande der Nikobaren-lnsel Kamortha beobachtete ich neuerdings diese Art [I have recently also observed this species in coastal sand from the Nicobar island Kamortha] (Sandstrand von Kamortha), (Sandstrand von Kamortha, Nicobaren I.)”, (Grunow 1867: 24; for the Nicobar Island specimens, these refer to two separate slides, see below); see Leuduger-Fortmorel 1898: 26, pl. V, fig. 7, [“Congo”] = our Fig. 2D), W: Grunow sample 790 (W0164898!, W0164899!) [Grunow kept two slides, which still exist: “Kalkbay”, cream-coloured original label, round cover slip (W0164898) and “Kalkbai”, green original label, square cover slip (W0164899), see Fig. 3B].

Figure 2. 

A. ‘Euodia Frauenfeldii Grunow’ (= Moralesonia frauenfeldii) reproduced from Grunow (1863: pl. 14, fig. 19a–d). B–C, E–G. Moralesonia frauenfeldii, specimens from Grunow sample 790 [2 slides, W0164898 (lectotype), W0164899, scale bar = 20 µm for all images]. D. ‘Eunotogramma Frauenfeldii’ (= Moralesonia frauenfeldii) reproduced from Leuduger-Fortmorel (1898: pl. V, fig. 7, “Congo”).

Figure 3. 

‘Eunotogramma Frauenfeldtii [sic]’ (= Moralesonia frauenfeldii), reproductions from Grunow’s drawings (C), notes in his catalogue (A), and slides in W for his sample 790 (B).

Lectotype (designated here)

Slide “Kalkbay” of Grunow sample 790 (W0164898!) lectotype designated here (= Fig. 2B, C, E–G, Grunow’s drawings, catalogue notes, and slides: Fig. 3A–C); BR [VI-41-B10 = Grunow sample 790 duplicate from W].

Isolectotypes (designated here)

SEM in Fig. 5A from subsample of the Kalk Bay raw material (Grunow sample 790 in BR); BM 57572! (Wynne Baxter 2943 = Grunow sample 790, duplicate from W = Fig. 4A–F), W [W0164899! = Grunow sample 790 “Kalkbai”], BRM HB-20 and BRM 24460, BM 10889! (“Kalkbai Cap d. g. Hoffn.”, L. H.[ardman] | 1132” (= Fig. 4G–I), BM 55989! (“Kalkbay”, ex Wynne Baxter 1361), BM 26220! (H.L. Smith, Diat. spec. typ. No. 659, “Cape of Good Hope original”; “In mare”), ANSP Febiger 3099, H.L.S.O A-98, H.L.Sm. EX 659 (Mahoney and Reimer 1997: 146).

Figure 4. 

A–F. Moralesonia frauenfeldii, specimens from BM 57572, isolectotype (scale bar = 20 µm); note that it is a slide made form Grunow sample 790. G–I. Moralesonia frauenfeldii, specimens from BM 10889 (“Kalkbai Cap d. g. Hoffn.”, L. H.[ardman] | 1132” (scale bar = 20 µm), isolectotype. J–K. Moralesonia frauenfeldii reproduced from Van Heurck (1883: pl. 126, fig. 14) and a reproduction in Grunow’s drawing collection for his sample 790 in W. L, M. specimens from BM Adams D875 (“Fundort? [locality?]”).

Figure 5. 

Moralesonia frauenfeldii, specimens from isotype material, a subsample of the Kalk Bay raw material (Grunow sample 790) from BR (none available any longer at W). A. Whole external view of valve, arrows indicate ‘unadorned’ holes, scale bar = 10 µm. B. Detail of external view of valve (as in Fig. 5A), scale bar = 5 µm. C. External view of valve with ribs evident by clear area, extending through to entire mantle, indicating it as part of valve, dividing valve into three ± equal parts, scale bar = 20 µm. D. Detail of cribra with well-developed, complex volate structure, usually with 2–4 pegs supporting complex (contorted) closing plate, scale bar = 5 µm. E. Internal view showing ribs, with detail in Fig. 5F, scale bar = 5 µm. G. Detail of valve surface with ‘unadorned’ holes (arrows), scale bar = 4 µm.

Registration

http://phycobank.org/104545

Analysed material

MOZAMBIQUE • Lourenço Marques [Maputo]; BM Adams TS 751! (figured in Desikachary 1988: pl. 583, fig. 8).

SIERRA LEONE • ‘Freetown’ (“The site at Freetown was in Fura Bay, which is on the south side of the estuary at a point where it is about 10 km wide”, Hendey 1957 [1958]: 29; one micrograph exists in the Hendey collection (specimen dimensions: 80 × 27 μm, Fig. 7G), slide not identified).

CONGO • Leuduger-Fortmorel (1898: 26, pl. V, fig. 7 = Fig. 2D; [“Cette petite Diatomée, très commune de la côte du Congo, a été determinée et nommée par M. le professeur Brun”, Leuduger-Fortmorel 1898: 24].

NICOBAR ISLANDS • Kamorta Island; “Auch im Strandsande der Nikobaren-lnsel Kamortha beobachtete ich neuerdings diese Art [I have recently also observed this species in coastal sand from the Nicobar island Kamortha”], W0164901! (“Sandstrand von Kamortha”), W0164902! (“Sandstrand von Kamortha, Nicobaren I.”), where the latter two designations in parentheses regarding locality refer to the two slides kept by Grunow for his sample 792 and are labeled as such; Grunow 1867: 24).

COUNTRY UNKNOWN • s.loc.; BM 59207! (I.[J.]D. Möller slide, Wynne Baxter 4591).

Description

Valves lunate, occasionally fusiform, length 32–62 μm, width 20–22 μm [measurements of type specimens from Grunow sample 790 (W0164898)], smaller valves tending towards ca 30 μm, width ± constant, forming less convex ventral margin. Each valve with two transapical ribs dividing valve into three ± equal parts. Ribs evident externally by clear area, extending through to entire mantle, indicating it as part of valve. Internally raised by 2–3 μm tapering towards mantle edge. Areolae ± round, radiating from eccentric hyaline centre, sometimes elongated. Rimoportulae absent. Few simple pores observed, randomly distributed on valve, notably near hyaline centre, absent elsewhere. Cribra with well-developed, complex volate structure, usually having 2–4(–6) pegs supporting complex (contorted) closing plate. External surface of valve finely ornamented. Girdle composed of few bands (3–4?), valvocopula and copulae, each with one curved row of areolae. Species synapomorphy: denser striation, less ornamented areolae.

Notes

In Grunow’s later description he notes that aside from the Kalk Bay locality (Grunow 1863: 158), “Auch im Strandsande der Nikobaren-lnsel Kamortha beobachtete ich neuerdings diese Art” (Grunow 1867: 24). Those specimens have been examined and, for the moment, are considered Moralesonia frauenfeldii (W0164901 & W0164902, slides for Grunow sample 792, Fig. 6A–F). Although not examined in detail here, Euodia gibba var. africana M.Perag. (in Tempère and Peragallo 1908: 83, nos 152–153, sample from ‘Algérie, Village-Négre, Oran, Terre fossile tertiaire’), the specimens are fragmented, but might possibly be interpreted as a species of Hemidiscus.

Figure 6. 

Moralesonia frauenfeldii. A–D. Specimens from Kamorta Island, Nicobar Islands, W0164902 (“Sandstrand von Kamortha, Nicobaren I.”). E. Slide W0164902 from W. F. Grunow’s catalogue notes on slides W0164901 & W0164902 (Grunow sample 792).

Moralesonia australis D.M.Williams, Ts.Georgiev, T.M.Schust. & C.E.Wetzel, sp. nov.

Fig. 7

Type locality

Australia, Carpentaria Bay (Arafura sea), BM 12829! (= Fig. 7E–F), holotype (= Cleve & Möller Diatoms [no.] 61, “Carpentaria Bay”, as Euodia Fraunfeldii Grunow), and BM Adams ‘Cleve & Möller [no.] 61’!, isotype. BM 31718! [Comber 927], “Carpentaria Golf”, Australia, J.D. Möller [no. 896, 1889]; BM 6481! (‘Euodia Fraunfeldii Grun. | Australien | J.D. Möller’, Fig. 7G), BM 60070! (J.D. Möller ex Wynne Baxter 6992); BM 74090! (J.D. Möller ex Wise [no.] 1918, “Australie”); BM 26837! (as “Eunotogramma frauenfeldii Grun. | Australie”, Van Heurck 1885: 118, sér. XXII, no. 526 = Fig. 7A–E) and BM Adams HVH 526!; W0164933! (Grunow sample 1484) (J.D. Möller, “Carpentaria Golf, Australia”), isotype, Fig. 7D, H–I, Grunow’s drawings, catalogue notes, and slide; BRM HB-19–20.

Figure 7. 

Moralesonia australis. A–C. Moralesonia australis, BM 26837 (as “Eunotogramma frauenfeldii Grun. | Australie.”, Van Heurck 1885: 118, sér. XXII, no. 526), scale bar = 20 µm. D, H, I. Grunow’s drawings, catalogue notes on his sample 1484 (W0164933), and slides. E, F. BM 12829 (Australia, Carpentaria Bay (Arafura Sea), holotype (= Cleve and Möller Diatoms [no.] 61, “Carpentaria Bay”, as Euodia Fraunfeldii Grun.)), scale bar = 20 µm. G. BM 6481 (“Euodia Fraunfeldii Grun. | Australien | J.D. Möller”), scale bar = 20 µm.

Registration

http://phycobank.org/104548

Description

Valves lunate, occasionally fusiform, length 55–65 μm, width 20–25 μm, width ± constant, forming less convex ventral margin. Each valve with two transapical ribs dividing valve into three ± equal parts. Ribs evident externally by clear area, extending through to entire mantle, indicating it as part of valve. Internally raised by 2–3 μm, tapering towards mantle edge. Areolae ± round, radiating from eccentric hyaline centre. Rimoportulae absent. Cribra detail not visible or preserved. Girdle unknown. Species synapomorphy: large and diffuse areolae.

Notes

It is quite possible that all the material cited above is from the same source: Carpentaria Bay (Arafura Sea), Australia, which is a reasonably large area. The notes on the material for Cleve and Möller slide no. 61 simply state “Comm.[unicavit] I.D. Möller [= Johann Diedrich Möller]” (Cleve and Möller 1878: 2).

Moralesonia sp.

Figs 8, 9A–I

Analysed material

ECUADOR • Galápagos Islands, Punta Espinosa, beach from Fernandina (Narborough) Island; 27 Jan. [19]67; I.L. Wiggins in Hendey (1971: 385, figs 16–18, CAS 211014–6, hypotypes 20032–20034, acc. no. 40287); BM 105488! (= Hendey 6702), BM 105494! (= Hendey 6708 = Fig. 8E, F), BM 105495! (= Hendey 6709), BM 105516! (= Hendey 6730) (Fig. 8C, D) • “Galápagos Islands, Santa Cruz […] 16th Aug. 1986, J.A. Broadhead” in Stidolph et al. (2012: pl. 24, fig. 58 = our Fig. 8B, https://pubs.usgs.gov/of/2012/1163/pages/Plates/24_Galapagos.pdf and https://planktonnet.awi.de/index.php?contenttype=image_details&itemid=60816#content).

Figure 8. 

Moralesonia sp. A. Hendey’s unpublished drawings of the specimens found in the Galápagos Islands. B. Reproduced from Stidolph et al. (2012: pl. 24, fig. 58 [inverted], Ecuador, “Galápagos Islands, Santa Cruz […] 16th Aug. 1986, J.A. Broadhead”), scale bar = 30 μm. C–F. Some of Hendey’s specimens. C–D. Ecuador, Galápagos Islands, Punta Espinosa, beach from Fernandina (Narborough) Island, 27th Jan. [19]67, I.L. Wiggins, BM 105516 (Hendey 6730). E–F. BM 105494 (Hendey 6708). G. “Eunotogramma frauenfeldii”, image from Hendey ms collection; specimen dimensions: 80 × 27 μm, scale bar = 20 µm.

BRAZIL • Pernambuco; J.D. Möller no. 893 [Möller 1889]; BM 31716! (Fig. 9A–C, one specimen), BRM HB-21.

Figure 9. 

A–I. Moralesonia sp. A–C. BM 31716, Brazil, Pernambuco, J.D. Möller [no. 893, 1889], one specimen, scale bar = 20 µm. D, H, I. Fossil material, BM 41317, Payne 7818, United States, California, “Patos guano”, specimen 71 × 25 µm, scale bar = 20 µm. E. BM Adams GC1451, Tempère, Nottingham, specimen 64 × 29 µm, scale bar = 20 µm. F. BM Adams H885, F. Adams, Hungary, Castel, specimen 72 × 23 µm, scale bar = 20 µm. G. BM10790, L. H.[ardman]| no. 4001, Philippines, Cebu [“Zebu”], one specimen, specimen 64 × 29 µm, scale bar = 20 µm. J. Moralesonia frauenfeldii, BM Adams GC 1450, East Africa, Ibo, ex W.A. Firth, scale bar = 20 µm.

PHILIPPINES • Cebu (“Zebu”); L. H.[ardman]| no. 4001 (Fig. 9G, one specimen); BM 10790!.

SOUTHERN PACIFIC OCEAN • J.D. Möller no. 24 [Möller 1892: 139: “Südlicher Stiller Ocean”] • J.D. Möller no. 832 [Möller 1897: 17].

PACIFIC OCEAN • Bahía Magdalena, sediments (BMS) [López Fuerte et al. 2010: pl. 14, figs 1, 2, smaller valves with two bars, not quite joining at centre].

COUNTRY UNKNOWN • s.loc.; BM Adams D875! (“Fundort? [locality?]”; many selected specimens, valve and girdle views, Fig. 4L, M); BM 104871! (Hendey 6060, 3 specimens).

Analysed fossil material

UNITED STATES • California, ‘Patos guano’; BM 41317! (Payne 7818) (Fig. 9D, H–I).

UNITED KINGDOM • Nottingham; BM Adams GC1451! (Tempère) (Fig. 9E).

HUNGARY • Castel; BM Adams H885! (F. Adams) (Fig. 9F).

Notes

Hendey’s unpublished drawings of the specimens found in the Galápagos Islands are reproduced here as Fig. 8A and some of the specimens are illustrated in Fig. 8C–F. Again, these have a superficial ‘similarity’ to the African specimens but, as yet, no specific character has been identified to associate them with Moralesonia frauenfeldii or to describe these specimens as a separate taxon. The three unpublished drawings are said to be from slides ‘Hendey 6701’ (= BM 105487), ‘Hendey 6708’ (= BM 105493), and ‘Hendey 6730’ (= BM 105516). Slide ‘Hendey 6701’ (= BM 105487) must be an error for 6702 (6701 is from San Diego; 6702 is labelled Eunotogramma frauenfeldii). In addition to the notebook, there are a series of unpublished Icones Diatomaceaearum documenting the Galápagos Islands study (Hendey 1971).

Moralesonia ? frauenfeldii

Figs 9J, 10

Analysed material

MOZAMBIQUE • East Africa, Ibo; BM Adams TS 457! (E. Leonard, no. 7); BM Adams TS 459! (E. Leonard, two specimens) (figured in Desikachary 1988: pl. 583, figs 2–4, 6, 7); BM Adams F16! (ex W.A. Firth) (figured in Desikachary 1988: pl. 583, fig. 1); BM Adams GC 1450! (ex W.A. Firth) (Fig. 9J).

MAURITIUS • Rodriguez (Île Rodriguez); Stub NHM I6 (see Fig. 10A–F).

Figure 10. 

Moralesonia sp., SEM images, specimens from Mauritius, Rodriguez (Île Rodriguez), stub NHM I6. A. Whole external view of valve, arrows indicate ribs, evident by clear area, extending through to entire mantle, indicating it as part of valve, dividing valve into three ± equal parts, scale bar = 10 µm. B. External view of pole, detail with absence of any pore-field, etc., scale bar = 1 µm. C. Detail of centre of valve, arrows indicating ‘unadorned’ holes, scale bar = 1 µm. D. Centre of valve with radiating ‘annulus’ (shown within white box), scale bar = 2 µm. E. External view of pole, with detail of cribra with well-developed, complex volate structure, scale bar = 1 µm. F. Additional external view of pole, with detail of cribra with well-developed, complex volate structure, scale bar = 2 µm.

Description

Valves lunate, occasionally fusiform, length 60–65 μm, width 20–25 μm, width ± constant, forming less convex ventral margin. Each valve with two transapical ribs dividing valve into three ± equal parts. Ribs evident externally by clear area, extending through to entire mantle, indicating it as part of valve. Internally raised by 2–3 μm tapering towards mantle edge. Areolae ± round, radiating from eccentric hyaline centre. Rimoportulae absent. Cribra detail not visible or preserved. Girdle unknown.

Discussion

With the description of Moralesonia and a preliminary estimate of its included species (ca 4–5), the relationships of the genus can be explored and the higher-level classification expanded, if applicable. As a starting point, the short history of the ‘Biddulphiées’ is worth recalling.

With the publication of the text accompanying his Atlas, Van Heurck (1885) revised his view on the status of Eunotogramma. None of the taxa described and noted in 1883 were discussed, with the exception of E. ? debilis Grunow (Grunow in Van Heurck 1883: pl. 126, figs 17–19; Van Heurck 1885: 202), for which Grunow had originally appended the name with a question mark. In 1885, Van Heurck’s order ‘Biddulphiées’ included a total of eight genera, of which Anaulus Ehrenb. was but one (Van Heurck 1885: 201; our Table 6, column 1). By 1896, Van Heurck’s classification appeared more complex than his earlier effort, the later version having four sub-families and numerous additional genera (Van Heurck 1896: xvi–xvii; our Table 6, column 2).

Table 6.
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Composition of Biddulphiaceae in Van Heurck (1885: 202), Van Heurck (1896: xvi–xvii; those genera marked * are sub-divided further, but these divisions are not discussed separately by Van Heurck) and Simonsen (1979: 50).

Biddulphiées (Van Heurck 1885) Biddulphiaceae (Van Heurck 1896) Biddulphioideae (Simonsen 1979)
I. Isthmieae
Isthmia C.Agardh Isthmia Isthmia
II. Hemiaulidieae
Terpsinoë Ehrenb. Terpsinoë* Terpsinoë
Anaulus [Eunotogramma] Anaulus [Eunotogramma]* Anaulus [Eunotogramma]
Hemiaulus Heib. Hemiaulus* Hemiaulus
+ seven other genera
III. Eucampieae
Lithodesmium Ehrenb. Lithodesmium
Eucampia Ehrenb. Eucampia*
Bellerochea Van Heurck Bellerochea
+ two other genera
IV. Eubiddulphieae
Biddulphia S.F.Gray Biddulphia* Biddulphia
+ eight other genera + 7 other genera

At first, Anaulus included only A. debilis (Grunow) Van Heurck (= Eunotogramma debile Grunow in Van Heurck 1883: pl. 126, figs 17–19). This species was assigned to the sub-genus (‘sous-genre’) Eunotogramma, but no other subgenera were recognised (or named) at that time (Van Heurck 1885: 202). This arrangement was modified in Van Heurck’s later book in which he explained: “I divide this genus [Anaulus] into the sub-genera Eu-Anaulus and Eunotogramma Auct., the latter being distinguished by the form of the valve being lunate (more or less crescent-shaped)” (Van Heurck 1896: 454). He included an illustration of Anaulus birostratus (Van Heurck 1896: 454, fig. 179, “California, Peru, Oamaru, the Balearic Islands, &c”), as an example of a “true Anaulus” (a member of Eu-Anaulus) and some illustrations of Anaulus debilis (from Ostend, Van Heurck 1896: pl. 19, fig. 626, pl. 34, fig. 892).

Anaulus debilis has many cross-members, similar to that seen in E. laevis, which was placed in Anaulus by Boyer (1901 [1900]: 737), now the type of the genus Eunotogramma (Amspoker 2011). Within the genus Eunotogramma, Boyer (1901 [1900]: 735) excluded all the larger species (those recognised above as ‘*Fossil’ in Table 5), suggesting that E. amphioxys is “equivalent to Biddulphia ? lunata E. […]” (another member of the ‘*Fossil’ group) and he divided Anaulus into two groups, one with “Valves elliptical” and the other “Valves lunate”, the latter equivalent to Eunotogramma. Van Heurck’s key appears more perplexing that his classification, but is illuminating with respect to characters used (Van Heurck 1896: 450, and page 510 regarding his concept of Euodia and Leudugeria, where he uses valve shape and the kinds of ‘puncta’ for Leudugeria, and shape and ‘a small pseudo-nodule’ for Euodia).

Simonsen’s classification differs little from Van Heurck’s (Table 6, column 3). His family Biddulphiaceae has three sub divisions. One of them, sub-family b, Biddulphioideae, includes 12 genera in all, Isthmia C.Agardh, Terpsinoë Ehrenb., Anaulus [Eunotogramma], Hemiaulus Heib., and Biddulphia S.F.Gray being amongst them (Simonsen 1979: 50).

Recent classifications are not much help. For example, Cox (2015) includes a number of redundant categories (following Round et al. 1990: 127), but still resulting in a classification similar to that of Van Heurck. The Order Anaulales has but one family, Anaulaceae, which has three genera: Anaulus, Eunotogramma, and Porpeia J.W.Bailey ex Ralfs (in Pritchard 1861: 850, 6–10 species, fossil). Nikolaev and Harwood proposed much the same, with the family Anaulaceae (placed within the order Biddulphiophycidae) composed of four genera: Anaulus, Eunotogramma, Porpeia, and Terpsinoë (Nikolaev and Harwood 2000: 52; Nikolaev et al. 2001: 41; Nikolaev and Harwood 2002: 78; Terpsinoë: Ehrenberg 1843: 402, with 20–30 species, fossil and extant). More recently, Anaulaceae has been modified in some online resources: both DiatomBase and AlgaeBase (19 Oct. 2023) include in Anaulaceae, along with Anaulus and Eunotogramma, Ceratanaulus Górecka et al. (in Witkowski et al. 2020: 14, a monotypic genus erected for Ceratanaulus creticus (Drebes & Schulz) Górecka et al., basionym: Anaulus creticus Drebes & Schulz (Drebes and Schulz 1981: 166); it is possible that Eunotogramma dubium maybe a second species of Ceratanaulus, see Table 5). Yet, the cladogram in Witkowski et al. (2020) places Ceratanaulus as sister to some species of Biddulphia (which divides into two separate groups, for further details see Sims et al. 2022 [2023]), and Terpsinoë plus Neocalyptrella Hern.-Becerril & Maeve, with other species of Biddulphia sister to Attheya T.West. Anaulus australis and Eunotogramma lunatum are sister to the Thalassiosirales.

Although not all major classifications have been discussed here, those from the 19th, 20th, and 21st century, more or less, follow one another (with the exception of the molecular cladograms) and base their relationships on the possession of ‘transapical ribs’ (‘costae’) and valve shape. In terms of formulating hypotheses of relationships, the data are limited, except to note that the genera Euodia, Eunotogramma, and Anaulus are all at present clearly non-monophyletic (as earlier noted for Anaulus by Drebes and Schulz 1981, and for Euodia and Eunotogramma by Sims 2000) and (most) monophyletic higher taxa are seemingly either non-existent or inconsistent. Thus, somewhat unsurprisingly, for Moralesonia, the currently most informative classification is still that of Van Heurck (1896). By informative, we mean, accounts for the potential synapomorphies of the included taxa at whatever rank. This will be explored in more detail in Part II of a series of papers around these taxa.

References

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