Ralfsiella smithii, P.A.Sims, D.M.Williams & Ashworth, 2018

Sims, Pat A., Williams, David M. & Ashworth, Matt, 2018, Examination of type specimens for the genera Odontella and Zygoceros (Bacillariophyceae) with evidence for the new family Odontellaceae and a description of three new genera, Phytotaxa 382 (1), pp. 1-56 : 42

Ralfsiella smithii (Ralfs in Pritchard) P.A. Sims, D. M. Williams & Ashworth, comb. nov. ( Figs 148–151 )

Basionym:— Cerataulus smithii Ralfs in Pritchard (1862: 847)

Synonyms:— Eupodiscus radiatus W. Smith (1853: 24 , pl. 30, fig. 255) non Eupodiscus radiatus Bailey (1851: 39) . Biddulphia radiata (W. Smith) Roper (1859: 9 , pl. 2, figs 27–29) Biddulphia smithii (Ralfs in Pritchard) Van Heurck (1885: 207) Biddulphia hemitropa L.W. Bailey (1862: 344 , pl. 2, figs 71–73) = Zygoceros hemitropus L.W. Bailey (1862: 344 , pl. 2, figs 71–73), nom. illegit.

Type:— Barking Creek (joining the river Roding to the River Thames), Roper ( BM 21225, specimen at Q41 4, England Finder), neotype, designated here.

Valve outline circular ( Fig. 148 ), lying opposite each other, a barely raised narrow elevation with a circular ocellus at summit ( Fig. 149 ). Valve face almost flat with a narrow slightly convex valve mantle bordering expanded hyaline valve margin ( Fig. 150 ). Valve face, mantle and elevations covered in irregular network of false pseudoloculi. Lying within each “loculus” a single, small poroid areola occluded by a velum, identical throughout valve, no specialised pores present ( Fig. 151 ). Equidistant between the elevations an external opening of rimoportula in submarginal position. Opening via a long slender tube, slightly wider at base than summit, while interior opening a slit across a papillus. Girdle bands with vertical rows of poroid areolae, valvocopula and remaining copulae open.

Observations:— Smith described his Eupodiscus radiatus from a few localities in England. Of these localities, Smith wrote: “…Detected by Mr. West among other Diatomaceae from the rivers Orwell and Thames” ( Smith 1853: 24). No relevant specimens could be found in either the in BM or BR William Smith collections (Van der Vijer, pers. comm.). Smith’s name, however, was a junior homonym of Eupodiscus radiatus Bailey (1851: 39) .

Roper transferred Smith’s species to Biddulphia as Biddulphia radiata (W. Smith) Roper (1859: 19 , pl. 2, figs 27–29) but this too is illegitmate as Smith’s Eupodiscus radiatus is invalid. Roper noted the same localities as Smith in his account, but added “…Barking Creek, Roper; Gorleston, Col. Baddley” ( Roper 1859: 9). A search of Roper’s collection yielded a number of slides that could be considered possible neotypes, in particular BM 21225 and BM 21231, both from Barking Creek. Of these, BM 21225 is preferred as it is marked as a type, the label makes reference to Roper’s Biddulphia paper and a specimen is indicated with coordinates. Thus, we have proposed this specimen as neotype.

Cerataulus smithii was proposed by Ralfs as a new name for Smith’s Eupodiscus radiatus .

Loren Bailey first named his species—described from Para River, Brazil —as “ Zygoceros hemitropus, Bail. , nov. sp.?” ( Bailey 1862: 344, pl.2, figs 71–73) but at the same time added the alternative name “ Biddulphia hemitropa L.W. B.” ( Bailey 1862: 344, pl.2, figs 71–73) and went on to note that these specimens should, indeed, belong in the genus Eupodiscus ( Bailey 1862: 344) . Later, in a final note, he wrote that “Mr. Stodder is inclined to think that the species here figured is a new one, and that the name Biddulphia hemitropa should be retained” ( Bailey 1862: 352). Given that a species cannot have two names, Bailey’s latter note suggests he favoured the genus Biddulphia . He goes on to compare Biddulphia hemitropa to Roper’s B. radiata distinguishing the two by the presence or absence of spines (slides are available in the Bailey collection, http://www2.huh.harvard.edu/diatom/baileycat.htm).

This description is based on specimens from Beaufort, South Carolina, USA.

At this time, two further species should be included in Ralfsiella but because of some complex nomenclatural issues, we offer below just the two new combinations. Details of both species will follow in a separate contribution.

Figures

FIGURES 148–152. Ralfsiella smithii (=Cerataulus smithii Ralfs in Pritchard) (Beaufort, South Carolina, USA). Fig. 148. Circular valve face with opposing narrow submarginal elevations; positioned midway submarginal hollow spines, the exterior openings of rimoportulae; valve surface covered in a mostly radial pattern of false pseudoloculi, valve mantle slightly indented where it joins narrow hyaline valve margin; scale bar = 10 μm. Fig. 149. Summit of elevation with rimmed ocellus; scale bar = 2 μm. Fig. 150. Frustule with attached girdle bands, flat valve face merging into rounded mantle, barely raised elevations; scale bar = 10 μm. Fig. 151. Irregular false pseudoloculi, basal layer with a single poroid areola occluded by a simple raised cribrum; scale bar = 1 μm.