Entogoniopsis grunowii J. Witkowski, P.A. Sims, N.I. Strelnikova & D.M. Williams, 2015

Witkowski, Jakub, Sims, Patricia A., Strelnikova, Nina I. & Williams, David M., 2015, Entogoniopsis gen. nov. and Trilamina gen. nov. (Bacillariophyta): a survey of multipolar pseudocellate diatoms with internal costae, including comments on the genus Sheshukovia Gleser, Phytotaxa 209 (1), pp. 448-450 : 448-450

2. Entogoniopsis grunowii J. Witkowski, P.A. Sims, N.I. Strelnikova & D.M. Williams , nov. sp.

(SEM: Figs 24–30 ; LM: Figs 31, 33–36 )

TYPE (here designated):— ‘ Oamaru , Otago, New Zealand’ (BM46607, holotype! = Fig. 34 ) .

Triceratium morlandii var. aperta Grunow (1888: 40 ; Grunow 1889: 388), nom. nud.

Entogonia davyana sensu Grove & Sturt (1887a: 8) non Entogonia davyana (Greville) Greville (1863: 236 ; basionym: Triceratium davyanum Greville 1862b: 232 , pl. 10, fig. 4).

Valve outline tripolar, with straight or slightly convex sides ( Figs 31, 33–36 ). Valve face undulate, with a triangular depressed central area surrounded by an elevated marginal zone ( Fig. 24 ). Low, stout polar elevations project above the raised zone of the valve face, and bear prominent pseudocelli, with conspicuously flattened summits ( Fig. 24 ). Along each side, the most distal part of the valve face gently slopes toward the mantle, and at the valve face-mantle junction, there is an inconspicuous hyaline marginal ridge extending between the pseudocelli ( Fig. 24 ). Whole valve face is perforated by poroid areolae occluded by external volae ( Figs 26–27 ). The areolae are more loosely arranged within the depressed valve centre (Fgs 31, 33–36). In the marginal zone of the valve face, areolae form parallel rows located within sectors bound by internal costae ( Figs 31, 33–36 ). If more than two rows of areolae are present within a sector, they are differentiated with respect to areola size and density, with the rows adjacent to internal costae comprising larger and more closely spaced areolae, and the rows located away from internal costae comprising smaller and more distantly distributed areolae (e.g., Fig. 33 ). Within the central depression, there is a central ring of rimoportulae, sometimes irregular ( Figs 27–28 ). Internal openings of the rimoportulae are in the form of slits across slightly raised papillae ( Fig. 28 ), and external openings take the form of short, non-buttressed tubes ( Fig. 27 ). Mantle is steep and shallow, with a smooth, hyaline margin that is slightly

ENTOGONIOPSIS GEN. NOV. AND TRILAMINA GEN. NOV. (BACILLARIOPHYTA)

Phytotaxa 209 (1) © 2015 Magnolia Press • 11 expanded inwardly ( Fig. 25 ). On some valves, immediately above the hyaline margin, there is a circumferential furrow extending along each side of the valve ( Fig. 24 ). Mantle is areolate; poroid areolae are arranged in rows generally parallel to the pervalvar axis, but less-well defined than rows on the valve face ( Figs 24–25 ). Mantle areolae also show variable diameters. On the valve interior, there is a prominent network of robust costae that extend between the mantle margin and the margin of the depressed central area ( Figs 25, 29 ). The internal costae define sectors for areolae both on the valve face and on the mantle ( Figs 25 , 31, 33–36 ). Girdle is composed of multiple closed bands. Valvocopula attaches to the internal costae by means of small clasping devices ( Figs 29–30 ), and to the expanded mantle margin by means of a fossa ( Fig. 29 ). The valvocopula is narrow, perforate, with poroid areolae arranged in rows parallel to the pervalvar axis ( Fig. 29 ). A detached closed copula with a fringed pars interior was also observed ( Fig. 29 ), bearing rows of poroid areolae similar to those on the valvocopula ( Fig. 29 ). Measurements (n =14): average side length: 68.43–263.85 µm; 2–4 coarser and 2–5 finer areolae in 10 µm; 2 costae in 10 µm, measured along the valve face margin; number of rimoportulae: 8–20; pseudocelli: 5–7 porelli in 10 µm.

Geographic and stratigraphic distribution ( Fig. 10, sites 12, 18–20):

(a) specimens:

Late Eocene: Falkland Plateau, South Atlantic: Vema Cruise 17, Core 107: BM stub P.1275 ( Figs 26, 28–30 ); South Tasman Rise, Southwestern Pacific Ocean: DSDP Site 281, Cores 281-14 through 281-16: SZCZ15073, 21078, 22054–22056, 22057 ( Fig. 33 ).

Late Eocene-earliest Oligocene: Oamaru , Otago, New Zealand: BM46607 ( Fig. 34 , holotype), BM63654 ( Fig. 36 ); BM coll. Adams: J671, G86; Oamaru Diatomite outcrops at: Allan’s Farm: BM coll. Adams TS426 ( Fig. 31 ); Jackson’s Paddock: BM coll. Adams F1348; ‘Railway Cutting 1’: BM coll. Adams G68 ( Fig. 35 ).

Early Oligocene: Falkland Plateau, South Atlantic: Vema Cruise 18, Core 112: BM stub P.1350 ( Figs 24–25, 27 ).

(b) records:

Late Eocene-earliest Oligocene: Oamaru , Otago, New Zealand: Reed (1991: pl. 17, fig. 215, as T. morlandii ); Desikachary & Sreelatha (1989: 260, pl. 63, fig. 3, as T. morlandii var. aperta ).

Observations:— Grove & Sturt (1887a: 8) reported a diatom they provisionally identified as Entogonia davyana (Greville) Greville (1863: 236 ; basionym: Triceratium davyanum Greville 1862b: 232 , pl. 10, fig. 4) from the fossil deposit in Oamaru , New Zealand. They provided no illustration and suggested that their specimens differed from E. davyana sensu stricto ( Fig. 32 ) by the absence, in the Oamaru specimen, of “the transverse lines [i.e., internal costae] in the central compartment, and the clear spaces at the base of each process [i.e., openings of the internal coil next to the proximal sides of polar elevations, see Fig. 4 ]”.

Subsequent to the series of papers published by Grove & Sturt (1886, 1887a,b,c) on the diatoms from Oamaru, Grunow (1887b , 1888) offered comments on numerous taxa proposed by them. With respect to Triceratium morlandii, Grunow (1888) wrote:

“ Tr. Morlandii Gr. et St. var. sub . aperta Grun. Formen, bei denen der Ring von Meschen, die das Centrum umgeben, an 3 Stellen mehr oder weniger geöffnet ist. Sehr ähnlich solchen Formen ist Entogonia Davyana Gr. et St. (nec Grev.), die Ref. vorläufig als var. aperta bezeichnet. Tr. venosum kommt bisweilen mit dreieckiger, erweiterter Mitte vor, und hat dann eine gewisse Aehnlichkeit mit letzterer. Die Autoren erwähnen noch brieflich eine dem Tr. venosum verwandte Form mit convexen Seiten und gebogenen Rippen, die sie als var. flexuosa bezeichnen. Vielleicht kann man alle diese Arten zu Entogonia ziehen” ( Grunow 1888: 40–41; spelling as in original).

Grunow’s views appeared in an English translation by G.C. Karop, with further annotations by Grove ( Grunow

1889: 388). The relevant paragraph of the translation reads:

“ Tr. Morlandii, Gr. and St. Herr Grunow proposes to add var. sub-aperta, Grun., for varieties in which the ring of meshes round the centre is more or less incomplete in three places. Such forms generally resemble Entogonia davyana, Gr. and St. (nec Grev.), which Herr Grunow provisionally designates var. aperta .”

Neither the German nor English text makes it clear whether Grunow was proposing his new variety for T. morlandii or E. davyana . In spite of the ambiguity in the German and English versions of Grunow’s accounts (1888, 1889), it has generally been accepted that Grunow meant Triceratium morlandii var. aperta : VanLandingham (1969; 1978) and the online Catalogue of Diatom Names ( Fourtanier & Kociolek 2011) list T.

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WITKOWSKI ET AL.

morlandii var. aperta rather than E. davyana var. aperta . Additionally, the Catalogue of Diatom Names identifies the name T. morlandii var. aperta as invalid but no discussion of its taxonomic status is evident.

Regardless of these nomenclatural issues, our observations indicate that Entogoniopsis morlandii sensu stricto differs from what we identify as Grunow’s var. aperta , and therefore the latter should be recognised as a species. Since the full name of the new variety was not explicitly stated by Grunow (1888, 1889), the name ‘ T. morlandii var. aperta ’, as far as we can tell, has never been validly published. As no valid name exists, these specimens constitute a new species, for which the name Entogoniopsis grunowii is proposed here.

Figures

FIGURES 24–30. Scanning electron micrographs of Entogoniopsis grunowii from Vema Cruise 18, Core 112 (Figs 24–25, 27) and Vema Cruise 17, Core 107 (Figs 26, 28–30), South Atlantic Ocean. Fig. 24: Oblique external view. Note the location of the hyaline marginal ridge below the highest level of the valve face (black arrow), and the central ring of rimoportulae (arrowhead). White arrow indicates the furrow above the hyaline margin of the mantle. Fig. 25: Oblique internal view, showing the location of the central ring of rimoportulae (arrowhead), bifurcations of costae on the mantle, and the inwardly expanded hyaline margin of the mantle. White arrow indicates the furrow above the hyaline margin of the mantle. Fig. 26: Detail of the specimen in Fig. 29, showing well-preserved volae. Fig. 27: Detail of the specimen in Fig. 24, showing fractured non-buttressed external tubes of the rimoportulae (arrow). Fig. 28: Detail of the specimen in Fig. 25, showing internal openings of the rimoportulae arranged in a regular ring. Fig. 29: Oblique internal view of a hypovalve with attached valvocopula (VC), and a detached band of the epicingulum showing a fimbriate edge (arrow). Fig. 30: Detail of the specimen in Fig. 29, showing clasping devices that attach the valvocopula to the internal costae (arrow).

FIGURES 31–36. Light micrographs showing the range of morphological variation in Entogoniopsis grunowii (Figs 31, 33–36) in comparison to Entogonia davyana (Greville) Greville (Fig. 32). Fig. 31: BM coll. Adams TS426, Allan’s Farm, Oamaru, New Zealand; Fig. 32: BM63959, Joe’s River, Barbadoes. Fig. 33: SZCZ15073, DSDP sample 29-281-16CC, South Tasman Rise. Fig. 34: BM46607, Oamaru, New Zealand, holotype. Fig. 35: BM coll. Adams G68, Railway Cutting 1, Oamaru, New Zealand. Fig. 36: BM63654, Oamaru, New Zealand.

FIGURES 1–5. An overview of valve morphology in Triceratium Ehrenberg sensu stricto and Entogonia Greville. Figs 1–2: Triceratium sp. aff. T. favus Ehrenberg. Fig. 1: Oblique external view showing rows of pseudoloculi on the valve face, marginal rows of rimoportulae (arrowhead), and polar ocelli (arrow). Fig. 2: Oblique internal view, showing internal openings of rimoportulae aligned in marginal rows (arrowhead). Fig. 3: Entogonia sp. Holmes & Brigger, oblique external view of a frustule with attached valvocopula. Note the polar and lateral exit pores of the internal coil, indicated by the arrow and arrowhead, respectively. Fig. 4: Entogonia davyana Greville in external valve view, polar exit pore indicated by the arrow. Fig. 5: Entogonia cloudi Holmes & Brigger, internal valve view, showing a well-preserved internal coil (arrow), and prominent internal costae (arrowhead).