Thumia Cleve ex F.B. Taylor 1926: 228

Williams, David M., 2021, Notes on the diatom collection of the Natural History Museum, London (BM) II- IV. Some type specimens in the genus Aulacodiscus Ehrenberg and nomenclatural notes on Thumia Cleve ex F. B. Taylor, Phytotaxa 480 (2), pp. 152-162 : 157-160

The genus Thumia Cleve ex F.B. Taylor 1926: 228

There are some differences of opinion as to the original publication of the diatom genus name Thumia . Before that can be established, three species names require consideration.

The first is Thumia oceanica Mereschkowsky (ex F. W. Mills 1935a: 1611). Mills writes “[ Thumia ] oceanica, Mer. Actinocyclus stictodiscus = STICTOCYCLUS ” ( Mills 1935a: 1611) and in an earlier part of his Index , he included the same taxon under the name Stictocyclus oceanica (Mereschkowsky ex F. W. Mills) F.W. Mills (1935b: 1491) . Mills probably added the name Thumia oceanica to his Index from one of the Thum slides in his possession. This would have been BM Adams J4132 ( Figure 27 , one of four specimens). This slide is dated (in pen) as 1913. The earliest appearance in print of the name Thumia oceanica , but without description or illustration, can be found in Nuckowski’s Catalogus Diatomearum, a not particularly well-known publication: […]: “266 Thum—SSel [= “praeparatum singulare cum aliquot diatomeis sełectis = Einzelpräparate = Single-Slides]—Südsee [South Pacific]—RM [Recent, marine]— Thumia oceanica Meresk. — Genus? species? ” ( Nuckowski 1917: 38). This is not a validly published name.

The second name is Thumia elegans Cleve ex Lefébure & Chenevière (1938: 11 , pl. 1, fig. 4, see Figure 28). Lefébure & Chenevière write: “Cette jolie forme a été mentionnée par Cleve dans sa correspondence de 1896 à 1900: il l’a dédiée au repute préparateur Thum 1 mais n’a donné aucune figure” ( Lefébure & Chenevière 1938: 11). Other citations can be found that refer simply to ‘ Thumia elegans Cleve ex Thum Slides’.

The third name is ‘ Thumia speciosa Cl. ’, a name that has never appeared in print and found only on the label of one slide in BM.

1 For biographical information on Eduard Thum (1847–1926) see http://microscopist.net/ThumE.html and http://www.microscopy-uk.eu/diatomist/ADvol21.pdf

First, what of the genus name? Most references cite Lefébure & Chenevière (1938: 11, pl. 1, fig. 4, see Figure 29) as its first place of publication. Fourtanier & Kociolek (2011) proposed an earlier validation to Lefébure & Chenevière found in Taylor’s still excellent little book Notes on Diatoms ( Taylor 1929: 228). Here Taylor writes:

Thumia Cleve in litt. M.f. 3a. I have a slide by Thum of a beautiful species of Aulacodiscus marked Thumia elegans Cl. from Pansram in Moravia. Thum wrote that Cleve has so named it. The center is flat, square or triangular, sloping down to the border. Radiating lines of fine, distinct beads run to the margin, with the usual intervals or furrows to the feet. A second slide by Thum, labelled Thumia oceanica Mer. is Actinocyclus stictodiscus (D.T.4768. V.H.S. 118.4) = Stictocyclus Mann ( Taylor 1929: 228; D.T. refers to De Toni 1894: 1173 [the 4768 refers to the species number for Actinocyclus appendiculatus Rattray , not the page number in De Toni]; V.H.S. refers to Van Heurck’s Synopsis des Diatomées de Belgique, 1883).

Of the two published species names, Thumia oceanica is certainly invalidly published as there is no description and in any case Mills referred it to another genus altogether, thus appearing to not accept it as a potentially valid name. Fourtanier & Kociolek (2011) concluded that as Taylor considered Thumia oceanica to be a synonym of Actinocyclus stictodiscus , the genus was validly described in Taylor (1929) and typified by the sole remaining species: Thumia elegans . But at that time (1929) Thumia elegans was not validly published either, so Taylor would be the first place of publication for the name Thumia elegans as well. Additionally, although the observation has never been published it was recognised by many that Thumia elegans is a synonym of Aulacodiscus gutwinskii Pantocsek (1909: 20 , pl. 1, fig. 1), both species being described from Pouzdřany (= Pausram), in the Czech Republic ( Pantocsek 1909: 20, pl. 1, fig. 1, see Figure 30; for details on the Pausram fossil deposit, see Ross and Sims 1985: 282). For example, the index card for Thumia elegans in the BM Adams collection was annotated by Robert Ross, who corrected the name to Aulacodiscus gutwinskii Pant. ; the Ferguson slide with a specimen of Thumia elegans (BM 66401) has the label corrected to Aulacodiscus gutwinskii and Ferguson’s reprint of the Lefébure & Chenevière 1938 paper has been corrected to Aulacodiscus gutwinskii (in pencil) as well.

If the genus name Thumia is accepted, the nomenclatural summary is as follows:

Figures

FIGURE 27. Thumia oceanica, BM Adams J4132; Figure 28: Reproduction of drawing of Actinocyclus stictodiscus (Grunow in Van Heurck 1883: pl. 118, fig. 4); Figure 29: Reproduction of drawing of Thumia elegans Cleve ex Lefébure & Chenevière (1938: 11, pl. 1, fig. 4); Figure 30: Reproduction of drawing of Aulacodiscus gutwinskii Pantocsek 1909: 20, pl. 1, fig. 1); Figure 31: Thumia gutwinskii (Pantocsek), Pouzdřany (= Pausram), South Moravia, BM Adams GC 3120 (‘Thumia elegans Cl., Mährer [Moravia]’), lectotype FIGURES 32–34. Thumia gutwinskii (Pantocsek), Pouzdřany (= Pausram), South Moravia, BM Adams J 4109 (‘Thumia elegans Cleve, Pausram, Moravia [Thum slide]’, with det. slip from Robert Ross added: ‘Aulacodiscus gutwinskii’).