Entogoniopsis polycistinora (Pantocsek ex Tempère) N.I. Strelnikova, P.A. Sims, J. Witkowski

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

3. Entogoniopsis polycistinora (Pantocsek ex Tempère) N.I. Strelnikova, P.A. Sims, J. Witkowski & D.M.

Williams, comb. nov.

(SEM: Figs 37–43 ; LM: Figs 44–49 , see also Figs 50–51 )

BASIONYM: Triceratium polycistinorum Pantocsek ex Tempère (1892 , Le Diatomiste 1: 119), nom. nov. = Entogonia saratoviana Pantocsek (1889: 97 , pl. VI, fig. 105), non ‘ Triceratium polycystinorum [sic] Pantocsek’ sensu Fenner (1985: 741, figs 13.10–13.11 = Entogoniopsis venosa ).

TYPE:— “Kusnetzk” (= Entogonia saratoviana Pantocsek ).

Triceratium globulifer Brun (1891: 47 , pl. XVI, fig. 15);

TYPE:— “Küsnetzk (fossile) Rare”.

Triceratium globulifer var. rotunda Brun (1891: 47 , pl. XVI, fig. 14);

TYPE:— “Küsnetzk (fossile) Rare”.

Triceratium subvenosum Hustedt in Wetzel (1935: 73, pl. 8, fig. 13);

TYPE:— “ Heiligenhafen an der Ostsee” (BRM Zt 1/18, holotype = Simonsen 1987: 184, pl. 294, fig. 1) .

Triceratium reedii Desikachary & Sreelatha (1989: 264) , nom. nov. = Triceratium forresterii Reed (1946: 294) non Triceratium forresterii (forresteri) Tempère in Bergon et al. (1890: 5, pl. 1, fig. 2);

TYPE:— Oamaru Diatomite outcrop at Forrester’s, New Zealand (CHR617491, holotype! of Triceratium forresterii Reed = Fig. 51 ).

Sheshukovia polycystinora [sic] (Pantocsek) Gleser (1984: 294).

Valves subrectangular in girdle view ( Fig. 40 ), valve outline tripolar ( Figs 44–49 ), with low polar elevations that have conspicuously flattened summits bearing prominent pseudocelli ( Figs 37–38 ). A low, sometimes inconspicuous, hyaline marginal ridge extends between the pseudocelli ( Fig. 40 ). Central part of the valve face flat ( Fig. 38 ) or gently depressed ( Figs 37, 39 ). In the central area there is a ring of rimoportulae ( Fig. 43 ), sometimes irregular ( Figs 38, 42 ). In some specimens, there are few rimoportulae also within the ring ( Fig. 43 ). The external openings of the rimoportulae are in the form of short, buttressed tubes ( Fig. 42 ). Rimoportulae open to the interior as slits between slightly raised lips ( Fig. 43 ). Valve face is perforated with poroid areolae, arranged in radial rows, sometimes gently curving toward the margin ( Figs 37, 38 ). Rows of areolae are grouped in sectors bound by internal costae ( Fig. 46 ). Between a pair of adjacent internal costae, there are usually two to four rows of areolae. Areolae within the rows immediately adjacent to internal costae are coarser and more closely spaced. The rows in the central part of a sector comprise smaller areolae that are more widely spaced ( Figs 37 , 51 ). The rows of areolae usually alternate. Areolae are occluded by volae ( Fig. 43 ). Mantle steeply downturned, relatively shallow, sometimes stepped ( Fig. 38 ). Mantle is perforate, except for the smooth hyaline margin, slightly expanded inwardly ( Figs 40–41 ). On the distal faces of the polar elevations, there are small, densely packed porelli, and between the poles, there are divergent rows of poroid areolae, clustered in sectors as on the valve face ( Figs 37–38, 40 ). A prominent network of robust costae, T-shaped in cross-section, is located on the valve interior ( Fig. 41 ). Costae generally radiate from a central hyaline area pierced by the rimoportulae ( Fig. 43 ). Closer to the valve face margin, costae gently curve away from the poles ( Figs 39 ; 44–49 ), and continue down the mantle until they fuse with the inwardly expanded hyaline mantle margin ( Fig. 41 ). A single detached closed copula was observed ( Fig. 39 ), bearing rows of densely packed poroids, parallel to the pervalvar axis. Measurements (n= 14): average side length: 70–178.5 µm; 3–5 coarser and 4–6 finer areolae in 10 µm; 2–3 costae in 10 µm, measured along the valve face margin; number of rimoportulae: 3–14; pseudocelli: 7–9 porelli in 10 µm.

Geographic and stratigraphic distribution ( Fig. 10, sites 1–7, 10–11, 14, 16–18):

(a) specimens:

Late Palaeocene: Kusnetzk, Penza District, Russia: BM61201 ( Fig. 49 ), BM63960, BM coll. Adams: GC3368, M89.

Early Eocene: Kamyshlov, Sverdlovsk District, Russia: BM stub P.1317 ( Figs 37, 39–43 ); BM63691 ( Fig. 47 ), BM63692 ( Fig. 46 ), BM66536 ( Fig. 44 ), BM78395; BM coll. Adams TS748 ( Fig. 45 ); Kirgizskoe diatomite bed, northwestern Kazakhstan: LECB stub 14 ( Fig. 38 ).

Middle-late Eocene transition: Mascarene Ridge, Indian Ocean, dredging DODO-123-D1: CAS 476021.

Late Eocene-earliest Oligocene: Oamaru Diatomite outcrop at Forrester’s, New Zealand: Reed (1946; CHR617491, Fig. 51 ).

Middle Eocene-early Miocene: Barbadoes: BM63693 ( Fig. 48 ).

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

Phytotaxa 209 (1) © 2015 Magnolia Press • 13

(b) records:

Late Campanian (Late Crateceous): Ust’ Man’ya, Severnaya Sos’va river, Tyumen’sk District, Pre-Polar Urals, Russia: Strelnikova (1974: 90, pl. XXXVII, figs 1a–d).

Late Palaeocene: Kusnetzk, Penza District, Russia: Pantocsek (1889: 97, pl. VI, fig. 105), Brun (1891: 47, pl. XVI, figs. 14–15).

Early Eocene: Kamyshlov, Sverdlovsk District, Russia: Hustedt (1959b: taf. 478, figs 23–24); ‘Eastern Slopes of Urals’, Berezovo, Khanty-Mansi Autonomous District, Russia: Krotov & Schibkova (1959: 118, figs 2.4–2.5).

Early-middle Eocene: North Atlantic Ocean: DSDP Site 552, Core 552-10: Baldauf (1984: pl. 13, fig. 9).

Middle Eocene : Lake Ashchikol’, South Kazakhstan: Schibkova (1968: 24); Staroverovka and Bolshaya Babka, Northern Donets Basin, Ukraine: Gleser et al. (1965: 81).

Late middle Eocene: Western North Atlantic Ocean: ODP Site 1051A, Core 1051A-13H; Site 1051B, Cores 1051B-7H through 1051B-16X: Witkowski et al. (2014).

Late Eocene: Heiligenhafen an der Ostsee: Wetzel (1935: 73, pl. 8, fig. 13), Hustedt (1959b: taf. 478, fig. 22); Western Siberia: Gleser et al. (1974: pl. XXIII, fig. 7).

Observations:— Triceratium polycistinorum was originally proposed by Pantocsek (1889) under the name Entogonia saratoviana from Kusnetzk. Earlier, a morphologically distinct species named Triceratium saratovianum Pantocsek (1889: 94 , pl. VII, fig. 122) was published precluding the transfer of E. saratoviana to Triceratium . Thus, Pantocsek proposed the replacement name Triceratium polycistinorum Pantocsek (in Tempère 1892: 119). Although we have not examined type material for E. saratoviana or T. saratovianum ( Pantocsek 1889: 94) , the line drawing of Triceratium saratovianum in Pantocsek (1889: pl. VII, fig. 122) shows distinct costae, presumably located on the valve interior, and a trifolium in the central part of the valve strongly suggesting that T. saratovianum should be transferred to Entogoniopsis . This action is taken below.

Brun (1891) also based his species Triceratium globulifer (and the variety rotunda ) on material from Kusnetzk. Considering the range of morphological variation documented here, Brun’s diatom is indistinguishable from Entogonia saratoviana Pantocsek. However , Brun’s taxonomic concept was relatively narrow: he considered the strongly produced poles and convexity of valve sides greater than that of Pantocsek’s species and took these to be a character supporting their separation. Nonetheless, Brun (1891: 47) commented on E. saratoviana that it cannot belong in Entogonia , and that it is most likely related to T. venosum Brightwell , with which we concur.

We have examined the holotype of Triceratium reedii (Reed) Desikachary & Sreelatha (1989) , originally published as T. forresterii by Reed (1946). Reed (1991) acknowledged that this species is a synonym of T. polycistinorum , and this view is supported here. Notably, however, Reed (1946) is the only record of Entogoniopsis polycistinora from southern mid-latitudes ( Fig. 10, site 18), and it extends the verified stratigraphic range of this species from the late Campanian to the Eocene-Oligocene transition, which is considerably longer than all other species of this genus.

Figures

FIGURES 37–43. Scanning electron micrographs of Entogoniopsis polycistinora from Kamyshlov, Russia (Figs 37, 39–43), and Kirgizskoe, Kazakhstan (Fig. 38). Fig. 37: Oblique external view. Location of the ring of rimoportulae indicated by the white arrowhead. Note spinules at the distal faces of the pseudocelli (white arrow). Black arrowhead indicates coarse areolae, and black arrow shows fine areolae in between rows of coarse ones. Fig. 38: Oblique external view of a specimen with a stepped mantle (arrow). Rimoportulae indicated by arrowhead. Fig. 39: Oblique internal view of a specimen with a ring of 14 rimoportulae located on a prominent central area (arrowhead). Fig. 40: Specimen in girdle view. Note the low relative height of the polar elevations, and the location of the hyaline marginal ridge (arrow). Fig. 41: Detail of a fractured valve revealing Tshaped cross-sections of the internal costae (arrowhead). Fig. 42: Detail of the specimen in Fig. 37, showing fractured buttressed external tubes of the rimoportulae. Fig. 43: Detail of the specimen in Fig. 39, showing internal openings of the rimoportulae, in the form of slits across slightly raised papillae. Note well-preserved volae (arrowhead).

FIGURES 44–49. Light micrographs showing the range of morphological variation in Entogoniopsis polycistinora. Fig. 44: BM66536, Kamyshlov, Russia. Fig. 45: BM coll. Adams TS748, Kamyshlov, Russia. Fig. 46: BM63692, Kamyshlov, Russia. Fig. 47: BM63691, Kamyshlov, Russia. Fig. 48: BM63693, Barbadoes. Fig. 49: BM61201, Kusnetzk, Russia.

FIGURES 50–51. Fig. 50: Reproduction of the line drawing of Entogonia saratoviana from Pantocsek (1889: pl. VI, fig. 105), not to scale. Fig. 51: Light micrograph of Triceratium reedii (Reed) Desikachary & Sreelatha, holotype, Forrester’s, Oamaru, New Zealand, slide CHR617491 (coll. Allan Herbarium, Landcare Research, New Zealand).