Monoportula uralensis (Strelnikova) Williams, David M., Sims, Pat A. & Witkowski, Jakub, 2023

Williams, David M., Sims, Pat A. & Witkowski, Jakub, 2023, Notes on the rare Cretaceous species Syndetocystis uralensis Strelnikova leading to the description of a new monotypic genus Monoportula P. A. Sims et D. M. Williams nov. gen., Phytotaxa 595 (2), pp. 219-224 : 220-222

Monoportula uralensis (Strelnikova) P.A.Sims & D.M.Williams nov. comb.

Registration: http://phycobank.org/103662

Basionym:— Syndetocystis uralensis Strelnikova 1974, p. 79 , tab. XXVII, figs 1–9

Type:— RUSSIA, Tyumen Oblast: Ust-Manya, N. Sosva River , “Eastern slopes of Pre-Polar Urals, Severnaya Sos’va River, Ust’-Man’ya Core 82, 145– 149.5cm […] diatomite; Campanian, plate XXVII, fig. 4” ( Strelnikova 1974, p. 79), Upper Cretaceous (Campanian), Paleofitol. Lab., VNIGRI (Leningrad), no. 137/3, holotype = Strelnikova (1974, p. 79, pl. XXVII, fig. 4, reproduced as our Figure 1 ); SEM images: “Core 82, Ust’Man’ya, basin of river Severnaya Sos’va, Tyumen’sk oblast”, Brigger ex Strelnikova (isotype specimens?), Stub P. 827 [“Pre-Polar Urals”, see Ross & Sims 1985, p. 279] .

Localities:— RussIA, BM 100282–4!: “Pre-polar Urals #8, Campanian, USSR ”; BM 99746: “Pre-polar Urals #10, Campanian, USSR ” (see Chambers 1997, p. 295, “Lwr. [=Lower] to Upr. [=Upper] Camp. [=Campanian] ( Strelnikova, 1974, Pre-Polar Urals)”, no illustration); BM 82242–3!: Kuril Islands, Russia (selected specimens, one per slide, Figs 2, 3 = specimen on BM 82242!: “ U.S. S. R. #1”; BM 82243!: “ U.S. S. R. #8”); SEM images: “ R 122 (ex Strelnikova)”, “ R 116 (ex Strelnikova)”, “ USSR #8”, “ USSR #10” https://doi.org/10.5519/qd.kep3mgsb, Natural History Museum 2022); In Strelnikova: “Occurrence: Polar Urals, River S’inya, aleuritic diatom clays, lower Campanian, single specimens. Pre-Polar Urals, Severnaya Sos’va River, aleuritic diatom clays, lower Campanian, diatomites and diatom clays, upper Campanian, single specimens” ( Strelnikova 1974, p. 79).

Illustrations:— Sims et al. (2006, p. 379, fig. 38, “ Syndetocystis uralensis Strelnikova. Core 82, Ust’Manya, Severnaya Sos’va, Campanian” = our Figure 6 and 10c).

Frustules cylindrical ( Figs 5, 6 ), valve face circular, flat ( Figs 1–6 ), diameter 40–90µm ( Strelnikova 1974: 49–94 µm diameter, 27–29μm deep including mantle). Valve face bordered by expanded marginal ridge separating it from vertical mantle, 15–33µm deep ( Figs 5, 6 ). Areolae poroid, on valve face arranged in interrupted radial and sub-radial rows extending from off-centre hyaline area from which a stout spine extends ( Figs 4–7 ). Scattered spinules cover valve face disturbing areolar arrangement ( Figs 5, 7 ). Mantle areolae in vertical rows situated between conspicuous hyaline marginal ridge up to 5µm deep and hyaline valve margin up to 7µm deep on valve exterior ( Fig. 7 ). Mantle areolae covered by network of anastomosing costae ( Figs 5, 6 ). Internally areolae sunk in rows between hyaline ribs ( Figs 8, 9 ) with ca. 14 areolae in 10µm within each row ( Strelnikova 1974: 15–16 in 10µm), areolae becoming more numerous towards valve margin ( Figs 5–7 ). One rimoportula present, its external opening through stout tube expanded at its summit, internally as slit, ca. 6µm long, between raised lips ( Figs 4–7 , arrow in Fig. 4 , LMs Figs 1–3 , arrow, Fig. 1 reproduced from Strelnikova 1974, tab. XXVII, fig. 4 = holotype), internally as slit between raised lips, situated obliquely relative to the valve face ( Figs 8, 9 , arrows in each).

Figures

FIGURES 1–7. Monoportula uralensis. Figures 1, reproduction of holotype image of Syndetocystis uralensis from Strelnikova (1974, p. 79, tab. XXVII, fig. 4), “Eastern slopes of Pre-Polar Urals, Severnaya Sos’va River, Ust’-Man’ya Core 82, 145–149.5cm […] diatomite; Campanian, plate XXVII, fig. 4” (Strelnikova 1974, p. 79), Upper Cretaceous (Campanian), rimoportula arowed; Figures 2, 3, LM specimen of Monoportula uralensis from BM 82242, Kuril Islands, Russia, “U.S.S.R. #1” (selected specimen, single mount, rimoportula arrowed); Figures 4–7, SEM, Figure 4, external view of whole valve, rimoportula arrowed, Figures 5, 6, external girdle view of frustule with mantle areolae covered as network of anastomosing costae, Figure 7, detail of Figure 5 showing the long extended tube of the rimoportula, bending towards mantle. Scale bars = 20μm (Figs 4, 5, 6), = 5μm (Fig. 7); Figs 4, 5, 7 from “R122”, Russia (BM Stub P1190), Figure 6 from “R116” (BM Stub P1100) both ex Strelnikova, possibly specimens from type material.

FIGURES 8, 9. Monoportula uralensis. Figures 8, 9, SEM, internal view of valve with rimoportula arrowed, Scale bars = 10μm (Figs 4, 5, 6), specimens from “Pre-polar Urals #8, Campanian, USSR” ex Strelnikova. FIGURE 10. Figure 10a, drawing of Syndetocystis uralensis from Van Heurck (1896, p. 432, fig. 155, after Chase & Walker 1887, pl. 4, fig. 13); Figure 10b is the same drawing modified to remove most of the periplekton leaving just a “thick, hyaline, tubular process”; Figure 10c, the same image as in Figure 5 but reversed, reduced in size and rotated 1800 to aid comparison with Figures 10a and 10b.