Ajacicyathina

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 : 450

Ajacicyathina family, genus, and species indet.

Fig. 79A, H, I .

Material. —Three phosphatised fragments, SMNH Sp11535– 11537, from sample 20/1B, Erkeket Formation, Khorbusuonka River, Siberia, Russia. Lower Botoman stage (correlated with the lower part of Cambrian Stage 4).

Remarks. —Phosphatic crusts replicating up to 6 mm long fragments of double walled initial parts of cups with simple rounded pores on the outer and inner walls and on the straight septa (vertical plate-like elements connecting the walls). Even distribution of rounded pores in combination with strait septa in the intervallum (cup space limited by walls) and absence of tabulae (horizontal plate-like intervallar elements) are indicative of the suborder Ajacicyathina . This suborder existed during the Tommotian–Toyonian stages (correlated with the Cambrian stages 2–4) and most of its representatives are known to have simple and almost undistinguishable morphologies at early stages of growth.

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).