Hyolithellus isiticus Missarzhevsky

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 : 431

Hyolithellus isiticus Missarzhevsky in Rozanov et al., 1969

Fig. 65B–E .

Material.—Several fragmentary tubes in calcium phosphate, including figured SMNH X11295–11298, from samples 11/19.5, lower Erkeket Formation, Khorbusuonka River and 21/21, Tyuser Formation, Lena River. Siberia, Russia; Dokidocyathus regularis Zone, Tommotian stage (correlated with the upper part of Cambrian Stage 2).

Remarks.—The tubes described by Rozanov et al. (1969: 150) have a smooth initial part similar to Hyolithellus tenuis Missarzhevsky in Rozanov and Missarzhevsky, 1966, intermediate part with faint transversal ribs as in Hyolithellus vladimirivae Missarzhevsky in Rozanov and Missarzhevsky, 1966, and well-developed flanges inclined towards the aperture at later growth stages. The available fragments suggest a diameter ca. 1 mm. External surface with faint transverse folds perpendicular to the longitudinal axis of the tube. The holotype derives from section Isit’ in the middle reaches of the Lena River, from the Dokidocyathus regularis Zone. Hyolithellus insolitus Grigor’eva in Voronin et al., 1982 (see Kouchinsky et al. 2015a) differs in having weaker concentric ribs without flanges and faint undulating longitudinal ridges and furrows between the ribs.

Stratigraphic and geographic range.— Dokidocyathus regularis Zone, Tommotian stage (correlated with the upper part of Cambrian Stage 2) through the Botoman stage (correlated with the Cambrian Stage 4), Siberia, Russia and equivalent beds in Mongolia, South China, India, Antarctica and Britain ( Rozanov et al. 2010: 59).

Figures

Fig. 65. Calcium phosphatic tubes of hyolithelminths from the lower Cambrian Erkeket Formation, Khorbusuonka River (A–C, G–J) and Tyuser Formation, lower reaches of the Lena River (D–F, K, L), Siberia, Russia; samples 11/19.5 (B, C), 19/3.25 (H, J), 19/4.25 (I), 19/5.5 (G), 19/16 (A), 21/21 (D, E, K), and 21/22 (F, L). A, F, H. Hyolithellus sp., SMNH X11299–11301, respectively. B–E. Hyolithellus isiticus Missarzhevsky in Rozanov et al., 1969, SMNH X11295–11298, respectively. G, I–L. Torellella spp., SMNH X11302–11306, respectively. Scale bar: 1 mm (D, L), 500 µm (A–C, E, F, H, I–K), and 250 µm (G).