Cambria sibirica Neckaja and Ivanova, 1956

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 : 424

Cambria sibirica Neckaja and Ivanova, 1956

Fig. 61D .

Material.—Two conjoined deformed valves of a phosphatised carapace, SMNH Ar75001, from sample 21/57.75, Tyuser Formation, Ulakhan-Ald’yarkhay, lower reaches of Lena River, Siberia, Russia. Delgadella anabara – Nevadella Zone, Atdabanian Stage (correlated with the Cambrian Stage 3).

Description.—Carapace (dorsal shield) is ca. 3.2 mm long. Prominent anterior lobe situated in the anterior cardinal area of each valve and forms a granulated cone with a blunt tip. Posterior lobe is lower, more extended and gently curved. Connecting lobe indistinct. Continuous admarginal ridge confluent with valve margin. The valve outer surface with granulose ornament.

Remarks.—For description of C. sibirica and comparison with other species see Williams et al. (1994), Vannier et al. (2005), Hinz-Schallreuter et al. (2008). Cambriid bradoriids are the oldest bradoriids known from Cambrian Stages 3 and 4 of Siberia, Gondwana and Laurentia (e.g., Melnikova et al. 1997).

Stratigraphic and geographic range.—Atdabanian stage (Cambrian Stage 3), Siberian Platform, Russia.

Figures

Fig. 61. Lobopodian (A) and bradoriid (B–D) calcium phosphatic fragments, from the lower Cambrian Erkeket Formation, Khorbusuonka River (B, C) and Tyuser (D), and Sekten (A) formations, lower reaches of the Lena River, Siberia, Russia; samples 19/3.25 (C), 19/31.75 (B), 21/57.75 (D), and 22/67 (A). A. Microdictyon robisoni Bengtson, Matthews, and Missarzhevsky, 1986, sclerite, SMNH X11294. B. Mongolitubulus spinosus (Hinz, 1987), spine, SMNH Ar75002. C. Mongolitubulus reticulatus Kouchinsky, Bengtson, Clausen, Gubanov, Malinky, and Peel, 2011, spine, SMNH Ar75003. D. Cambria sibirica Neckaja and Ivanova, 1956, carapace, SMNH Ar75001; D1, anterior view; D2, D3, dorsal view. Scale bar: 250 µm A–C) and 1.25 mm (D).