Gyrocylindrus Strelnikova & Nikolaev 1995: 93

Gyrocylindrus Strelnikova & Nikolaev 1995: 93 .

Type: Gyrocylindrus antiquus Strelnikova & Nikolaev 1995: 94

Heterotypic synonyms “ Pyxilla multiseptata ” Gleser, 1995 : [132] pl. 1: fig. 16, nom. inval.

Cylindrospira simsiae f. simsiae Mitlehner 1996: 323 (‘ simsi ’)

Cylindrospira simsiae f. homanniae Mitlehner 1996: 325 (‘ simsi ’)

Type locality: Russia: “ Regio Volgensis , prov. Ulianovsk, opp. Sengilei, mons Granoe Ucho dictus ” […] [Sengiley, mountain Granoe Ukho]”

Holotype: “ Collectio in cathedra Botanicae facultatis Edaphobiologicae Universitatis Petropolitanae conservatur ”, sample 58 ( Strelnikova & Nikolaev 1995, figs 2–7, holotype).

Other material: Denmark: Knudeklint: Island of Fur, sample level ‘D 292’ [“Knudeklint/Stolleklint (Steilufer) | Cementsteine | zwischen A-22 und A-29”] ( Homann 1991 [p. 18)]” ( BM 82367 [missing], holotype specimen of Cylindrospira (‘ simsi ’) simsiae f. simsiae at England Finder N 34.3, lost); BM 82366, two selected specimens: specimen 1, to the left = Mitlehner [‘1995’] 1996, figs 12, 13, 16, 17 = lectotype (designated here); specimen 2, to the right = Mitlehner [‘1995’] 1996, figs 14, 15, isolectotype; “SEM stub D 292” holotype of Cylindrospira simsiae f. homanniae , lost = Mitlehner [‘1995’] 1996, figs 6, 7 = lectotype (designated here).

† Although not effectively published, Mitlehner in his thesis, initially recognized two species of Cylindrospira rather than two forms of one species and provided BM numbers for the type of each. These numbers ( BM 82284–6) were subsequently assigned to other specimens in the BM collection unrelated to Mitlehner’s study (1995). Mitlehner illustrated Cylindrospira simsiae Mitlehner (‘ simsi ’) with eight figures (pl. 11, figs 1–8) and a line drawing (that remained unpublished, Mitlehner 1995: 149) and ‘ Cylindrospira homannii ’ with three figures (pl. 11, figs 9–11). The published holotype figure of Cylindrospira simsiae f. simsiae in Mitlehner [‘1995’] 1996: figs 12, 13, 16, 17 = Mitlehner 1995: pl. 11, figs 1, 5, 6, 8; the published holotype figure of Cylindrospira simsiae f. homanniae in Mitlehner [‘1995’] 1996, fig. 7 = Mitlehner 1995: pl. 11, fig. 9 (oriented differently).

‡ This stub cannot be found, thus the published images will be the holotype.

Gleser, S.I. (1995). Diatom and silicoflagellate assemblages as indicators of synchronous occurrence of diatomites of Middle Volga region, Denmark and Lower Palaeogene oceanic bottom sediments. In: Barash M. S. (ed.), Recent and fossil microplankton of the World Ocean. Nauka, Moscow (in Russian, with English title), pp. 57–63.

Homann, M. (1991). Die Diatomeen der Fur–Formation (Alttertiär, Limfjord/Dänemark). Geologisches Jahrbuch Reihe A 123: 1–285.

Khokhlova I. E. & Oreshkina T.V. (1999). Early Palaeogene siliceous microfossils of the Middle Volga Region: stratigraphy and palaeogeography. In Crasquin-Soleau, S. & De Wever, P. (eds), Peri-Tethys: stratigraphic correlations 3. Geodiversitas 21 (3): 429–451.

Mitlehner, A.G. (1995). The occurrence and preservation of diatoms in the Palaeogene of the North Sea Basin. Doctoral thesis, University College London.

Available at: https://discovery.ucl.ac.uk/id/eprint/10104683/

Mitlehner, A.G. (1996 ‘1995’). Cylindrospira, a new diatom genus from the Palaeogene of Denmark with palaeoecological significance. Diatom Research 10: 321–331.

Oreshkina, T.V. & Oberhänsli, H. (2003). Diatom turnover in the early Paleogene diatomite of the Sengiley section, Middle Povolzhie, Russia: A response to the Initial Eocene Thermal Maximum? In Wing, S.L., Gingerich, P.D., Schmitz, B. & Thomas, E., eds., Causes and Consequences of Globally Warm Climates in the Early Paleogene, Geological Society of America Special Paper 369, pp. 169–179.

Oreshkina, T.V. & Aleksandrova, G.N. (2007). Terminal Paleocene of the Volga Middle Reaches: Biostratigraphy and Paleosettings. Stratigraphy and Geological Correlation 15: 206–230.

Strelnikova, N.I. & Nikolaev, V.A. (1995, post 17 th Oct.). Novy rod Gyrocylindrus (Bacillariophyta) iz paleogenovich otlozeny Rossiii i Danii. (A New Genus Gyrocylindrus (Bacillariophyta) From Paleogene Deposits of Russia and Denmark). Botanicheskii Zhurnal 80 (8): 93–98.

Witkowski, J. (2022 In review). Early Paleocene-Late Eocene diatoms from the Blake Nose, western North Atlantic Ocean.