Aetholicopalla

Kouchinsky, Artem, Bengtson, Stefan, Clausen, Sébastien & Vendrasco, Michael J., 2015, An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia, Acta Palaeontologica Polonica 60 (2), pp. 421-512 : 506

Aetholicopalla adnata Conway Morris in Bengtson et al., 1990

Fig. 73A

Material.— One specimen, SMNH X 4823 , from sample 7/70; uppermost Emyaksin Formation , Bol’shaya Kuonamka River ; Calodiscus-Erbiella Zone, lower Botoman Stage .

Description.—Phosphatised globule, ca. 1 mm in diameter. The surface is semi-spherical, densely covered with bumps, 20–40 μm wide, having open or broken-off tips. The other side is smooth and slightly concave, with rare bumps and a curved channel-like cast in the middle ( Fig. 73A 2 ).

Remarks.—While otherwise similar to Aetholicopalla adnata, the fossil does not display a double-wall or tubular pillars. The fossil also resembles single-walled Archaeooides in having a regular pustulose surface, but has a flattened portion typical of Aetholicopalla adnata and presumably related to an encrusting habit. Globules frequently occur in the samples, but their preservation prevents identification. Globules, 0.5–1 mm in size, with sphaerical or distorted wall often bearing tubercles occur in samples K7-6.3B, 6/16, 3/8, 3/11, 3/16.5, 3/23, 3/34, 3/40, 3/53.5, from the Emyaksin Formation of the Malaya Kuonamka and Bol’shaya Kuonamka rivers, ranging from the Dokidocyathus regularis Zone, Tommotian Stage to the Delgadella anabara Zone, Atdabanian Stage. Smaller globules of unknown affinity, 0.15–0.3 mm in size, of which deformation often produces a tri-lobate shape ( Fig. 73B ), occur in samples 3/29, 3/49, 3/50, 3/62.5, 6/59.3, K7-6.3B, 7/27.5, and 7/34.7 from the Tommotian and Atdabanian strata of the same localities.

Stratigraphic and geographic range.— Aetholicopalla adnata is also described from Cambrian Series 2 of the Montagne Noire, France ( Kerber 1988) and the Görlitz Syncline, eastern Germany ( Elicki and Schneider 1992; Elicki 1998), Australia ( Bengtson et al. 1990; Gravestock et al. 2001), Antarctica ( Wrona 2004), and from the Series 2–3 boundary interval of Sardinia ( Elicki and Pillola 2004).

Figures

Fig. 73. Globules from lower Cambrian Emyaksin Formation, Bol’shaya Kuonamka River and Malaya Kuonamka River, Anabar Uplift, Siberia. A. Aetholicopalla adnata Conway Morris in Bengtson et al., 1990, SMNH X 4823, sample 7/70; lateral (A 1) and upper (A 3) views; A 2, view on the flattened side presumably representing attachment surface. B. Globule showing symmetrical tri-lobate deformation, SMNH X 4824, sample 3/50; plan (B ) and lateral (B ) views. Scale bar: A, 600 μm, B, 300 μm.

Fig. 2. Derivation of fossiliferous samples (arrows with numbers) and chemostratigraphic correlation of sections 1 and 3 (Malaya Kuonamka River) with sections 6 and 7 (Bol’shaya Kuonamka River). Correlation with carbon isotope features II–VII from stratotypes of south-eastern Siberian Platform (Brasier et al. 1994) according to Kouchinsky et al. (2001). Note that the zero level in all sections corresponds to the water level above which the sections were exposed in 1996. Description of fauna from the lower part of the Emyaksin Formation in complementary outcrops at the Bol’shaya Kuonamka River (below that zero level) will be published elsewhere. Fauna from the overlying Kuonamka Formation is published by Gubanov et al. (2004) and Kouchinsky et al. (2011).