Parailsanella 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 : 377

Parailsanella sp.

Fig. 24G, H .

Material.—Several calcium phosphatic internal moulds from sample 21/54, Tyuser Formation, Delgadella anabara – Nevadella Zone, Atdabanian stage , 22/0 from top Tyuser Formation, Bergeroniellus micmacciformis –Erbiella Zone, lower Botoman stage (correlated with the lower Cambrian Stage 4), and 22/50 from the Sekten Formation, upper Toyonian stage (correlated with the Cambrian Stage 4) and including two figured specimens, SMNH Mo194707 and 194708, from sample 22/50. Ulakhan-Ald’yarkhay, lower Lena River. Siberia, Russia.

Remarks. —Slightly cyrtoconic, laterally moderately compressed conical calcium phosphatic internal moulds with oval aperture (length/width ratio ca. 2), regular transverse ribs and bulbous apex. Those steinkerns may represent different species, but their overall morphology is compatible with species of Parailsanella , notably Parailsanella sp. 2 from the lower Cambrian Stage 4 (herein) of Siberian Platform ( Kouchinsky et al. 2015a: fig. 7) and Parailsanella luonanensis Li, Zhang, Skovsted, Yun, Pan, and Li, 2019 , from Series 2 of North China.

Figures

Fig. 24. Molluscs from the lower Cambrian Erkeket Formation, Khorbusuonka River (A–F, J–N) and Sekten Formation, lower reaches of the Lena River (G–I), Siberia, Russia; samples 11/2B (E, F, J), 11/16.1 (K, M, N), 19/12.75 (A), 19/11.75 (B), 20/1B (L, O, P), 20/6B (C, D), and 22/50 (G–I). A, B. Davidonia anabarica (Parkhaev, 2005), internal moulds, SMNH Mo194701 and 194702, respectively. C. Mellopegma sp., internal mould, SMNH Mo194713. D. Stenotheca cf. drepanoida (He and Pei in He et al., 1984), silicified shell, SMNH Mo194714. D1, lateral view; D2, oblique apertural view. →