Cambrocyathellus sp.

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 : 452

Cambrocyathellus sp.

Fig. 79F .

Material. —A single phosphatised fragment SMNH Sp11543 from sample 21/21, Tyuser Formation, Lena River, Siberia, Russia. Dokodocyathus regularis Zone, Tommotian stage correlated with the upper part of Cambrian Stage 2).

Remarks. —Fragment of the outer wall pierced by relatively large pores of rounded shapes and uneven sizes, 80–140 µm in dimeter. Ridges representing remains of vertical plate-like elements are observed on the inner surface of the wall. Outer walls with irregularly situated pores of variable sizes are more characteristic of archaeocyathids than ajacicyathids, while the presence of septum-like elements infers the affinity to the Loculicyathina (Debrenne et al. 2015). Two vertical rows of pores per each interseptal space is typical of Cambrocyathellus Zhuravleva, 1960 , which is known on the Siberian Platform from the Tommotian and lowermost Atdabanian (correlated with the lower part of the Cambrian Stage 3) strata ( Zhuravleva 1960; Zhuravlev et al. 1983).

Figures

Fig. 79. Archaeocyatha, phosphatized fragments from the lower Cambrian Erkeket (A, D, H, I) and Chuskuna (E) formations, Khorbusuonka River and Tyuser Formation, lower reaches of the Lena River (B, C, F, G), Siberia, Russia; samples 15/23 (E), 20/1B (A, D, H, I), and 21/21 (B, C, F, G). A, H, I. Ajacicyathina family, gen. and sp. indet., fragments of cups with simple rounded pores, SMNH Sp11535–11537, respectively. A1, H1, lateral view; A2, basal view; H2, oblique lateral view showing inner part of the cup. B, E. Cryptoporocyathus junicanensis Zhuravleva, 1960. B. Wall fragments, SMNH Sp11538–11539, respectively. B1, inner surface of the wall. B2, outer surface of the wall. E. Wall fragment, SMNH Sp11540. C. Dictyocyathus sp., fragment of an intervallar dictyonal network, SMNH Sp11541. D. Carinacyathus sp., fragment of a cup wall with geniculate tubular canals, SMNH Sp11542. F. Cambrocyathellus sp., fragment of a cup, SMNH Sp11543. G. Possible archaeocyath pelta (upper covering structure of the cup), SMNH Sp11544. Scale bar: 1.25 mm (C), 500 µm (B, F–I), and 250 µm (A, D, E).