Platysolenites antiquissimus Eichwald, 1860

Kouchinsky, Artem, Alexander, Ruaridh, Bengtson, Stefan, Bowyer, Fred, Clausen, Sébastien, Holmer, Lars E., Kolesnikov, Kirill A., Korovnikov, Igor V., Pavlov, Vladimir, Skovsted, Christian B., Ushatinskaya, Galina, Wood, Rachel & Zhuravlev, Andrey Y., 2022, Early-middle Cambrian stratigraphy and faunas from northern Siberia, Acta Palaeontologica Polonica 67 (2), pp. 341-464 : 436-437

Platysolenites antiquissimus Eichwald, 1860

Fig. 67H, I .

Material.—SMNH X11322 and X11323, from sample 15/23, Chuskuna Formation (upper part of the Kessyusa Group), Khorbusuonka River, Siberia, Russia. Watsonella Zone, Cambrian Stage 2.

Remarks.—Somewhat compressed fragments of tubes, 0.5–1 mm long and 0.2–0.3 mm in original diameter, with granular (presumably agglutinated) composition of the wall, ca. 20 μm thick. Similar fossils are described from the Fortunian stage and lower part of Cambrian Stage 2 outcrops of the Nemakit- Daldyn, Manykay, Medvezhya and lower Emyaksin formations on the Anabar Uplift (Kouchinsky et al. 2017).

Stratigraphic and geographic range.—Uppermost Ediacaran? ( Kontorovich et al. 2008; Zhuravlev et al. 2012), Terreneuvian Series of Siberia, Baltica, Laurentia, and Avalonia ; Cambrian Stage 3 of Baltica, Laurentia, Avalonia, and Armorica ( McIlroy et al. 2001; Streng et al. 2005, Kouchinsky et al. 2017).

Problematic tubular fossils

Fig. 69A–I .

Remarks.—Other problematic tubular fossils are represented by silicified tubes, 50–120 µm in diameter and up to 3 mm long. Their walls are smooth but showing occasional swellings probably produced or enhanced by diagenetic silicification. Originally, the tubes were not rigid that is suggested by deformations, such as irregular curvature and obliteration in places. The initial part of the tubes is open and goblet-shaped ( Fig. 69H 2 ).

An array of irregularly curved phosphatised tubes ( Fig. 69A ) loosely arranged in the same direction is found attached to a shell fragment ( Fig. 32A 2 ). The tubes may represent cyanobacterial trichoms. They are 5–10 µm in diameter and up to 200 µm in visible length, smooth, without visible partitioning.

A set of four incompletely preserved straight and smooth phosphatised tubes, 100–150 µm in diameter, attached to each other longitudinally may represent a fragment of tabulatomorph colonial coral ( Fig. 69I ). The fragment is ca. 600 µm long. Distinct septation is not revealed. One of the tubes is apparently closed by a gently concave tabula ( Fig. 69I 1 ).

Phylum Porifera Grant, 1836

Class Hexactinellida Schmidt, 1870

Order and family uncertain

Genus Thoracospongia Mehl, 1996

Type species: Thoracospongia follispiculata Mehl, 1996 ; Florian–Undillan stages (Wuliuan–Drumian stages), Miaolingian Series, Cambri- an; Georgina Basin, Queensland, Australia .

Figures

Fig. 67. Anabaritids, internal moulds (A–F) and other problematic tubes G–I) from the lower Cambrian Kessyusa Group (B–D, H, I) and Erkeket Formation (A, E–G), Khorbusuonka River, Siberia, Russia; samples 11/16.05 (A), 11/2B (E, F), 15/23 (B–D, H, I), and 20/1B (G). A. Anabarites tristichus Missarzhevsky in Rozanov et al., 1969, SMNH X11315. A1, transversal view of the tube; A2, lateral view. B. Anabarites hexasulcatus (Missarzhevsky, 1974), SMNH X11316. C. Selindeochrea ternaria Missarzhevsky inRozanov etal.,1969),SMNHX11317.D.Cambrotubulus sp., SMNH X11318.E, F. Anabarites korobovi (Missarzhevsky in Rozanov and Missarzhevsky, 1966), SMNH X11319 and 11320, respectively. G. Coleolella billinsi (Sysoev, 1962), SMNH X11321. H, I. Platysolenites antiquissimus Eichwald, 1860, SMNH X11322 and 11323, respectively. Scale bar: 250 µm (A) and 500 µm (B–I).

Fig. 69. Problematic fossils from the lower Cambrian Erkeket Formation, Khorbusuonka River, Siberia, Russia; samples 11/16.1 (K), 19/11.75 (A, I), 19/12.75 (B), 19/16 (D, F, G, H), 19/18 (C, E), and 19/5B (J). A. Tubular diagenetically phosphatised cyanobacterial trichomes, SMNH X11337. B–H. Problematic silicified tubes, SMNH X11338–11344, respectively. H2, enlargement showing presumably initial part of the tube. I. Problematic phosphatized tubes longitudinally merged, SMNH X11345. I1, close-up of I2, showing apertures of the tubes. J. Globula, SMNH X11346. K. Disk-like fossil, SMNH X11347. K1, plain view; K2, lateral view. Scale bar: 500 µm (B–G, H1), 250 µm (I2, J, K), 125 µm (I1), 50 µm (A, H2).

Fig. 2. Stratigraphic columns of sections 96-1 and 96-2, Malaya Kuonamka River and section 96-8, Bol’shaya Kuonamka River, Siberia, Russia (after Kouchinsky et al. 2011: fig. 2). Arrows with numbers indicate derivation of fossiliferous samples. Botoman Stage is correlated herein with the Cambrian Stage 4, in accordance with Geyer (2019).Asterisk A, indicates occurrences of Davidonia anabarica, Enigmaconus? pyramidalis, Pelagiella sp. 1 and 2, Majatheca tumefacta, Tetratheca clinisepta, “Lenatheca groenlandica”, Conotheca cf.mammilata, Parkula cf. esmeraldina (see Kouchinsky et al.2015a). Asterisk B, indicates occurrences of Anabaroconus sibiricus, Eotebenna viviannae, Kuonamkaella oliva, Leptostega cf. hyperborea, Pelagiella sp. cf. Cambretina mareki, Pelagiella sp. cf. Costipelagiella zazvorkai, Pojetaia dentifera, Protowenella sp., Pseudomyona queenslandica, and Yochelcionella angustiplicata (see Gubanov et al. 2004b and Kouchinsky et al. 2011). Abbreviations: Ac., Acadoparadoxides; An., Anabaraspis; B., Bergeroniellus expansus; P., Paramicmacca; Fm., Formation; H., Homotreta; O-S, Ovatoryctocara–Schistocephalus; T., Triplagnostus.

Fig.32.Problematic shell 2, from the lower Cambrian Erkeket Formation,Khorbusuonka River, Siberia,Russia;samples 19/11.75 (A–C,E) and 19/10.25(D). A–E. Phosphatised fragments of shells with spines, SMNH X11039–11043, respectively.A1, D1, plain view; A2, lateral view of the shell fragment with cyanobacterial filaments (SMNH X11337, see Fig. 69A) attached to its inner side (bottom); A3, close-up showing spines; D2, lateral view. C, E, fragments of presumably subapical part of the shell. E1, E2, view on the same fragment, ca 90º rotated around the longitudinal axis. Scale bar: 250 µm (C, E), 165 µm (A1, A2, B1, D), and 50 µm (A3, B2).

Fig. 1. Locality maps. A. Map of the Siberian Platform. B. Khorbusuonka River. Localities referred to in the main text: 96-1, 96-2, 96-3, Malaya Kuonamka (MK) and 96-6, 96-7, 96-8, Bol’shaya Kuonamka (BK) rivers, eastern flank of the Anabar Uplift; 3, 11, 15, 19, 20, Khorbusuonka River, Olenyok Uplift; 21, 22, Lena River lower reaches, Ulakhan-Ald’yarkhay Brook; Le, Lena River middle reaches, Tiktirikteekh and Bydyangaya Brooks; Al, Aldan River, between sections “Dvortsy” and Ulakhan- Sulugur. Margin of the Siberian Platform is shown by a dashed line in A.