Halkieria sp.

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 : 456

Halkieria sp.

Fig. 33 .

Material.—Single phosphatised sclerites from samples 7/25.6 SMNH X 4666), 7/27.5, and 7/36.7 (SMNH X 4667). Emyaksin Formation, Bol’shaya Kuonamka River; correlated with the interval of Profallotaspis jakutensis – Delgadella anabara zones, Atdabanian Stage.

Description.—Asymmetrical, elongated, blade-like and curved sclerites with transversely convex lower and upper sides. The base of sclerites has a rounded triangular, broad ( Fig. 33A 1 ) or extended narrower ( Fig. 33B 2 ) aperture surrounded by undulating walls with auricules. Wall microstructure consists of aciculate elements assembled in broad laths, arranged in transversal rows ( Fig. 33A 3 ; see also Bengtson et al. 1990; Porter 2008).

Figures

Fig. 33. Halkieriid Halkieria sp. from lower Cambrian Emyaksin Formation, Bol’shaya Kuonamka River, Anabar Uplift, Siberia. A. SMNH X 4667, sample 7/36.7; A1, plan view on the lower side of sclerite and its aperture; A2, oblique lateral view; A3, close-up of A2, fibrous microstructure. B. SMNH X 4666, sample 7/25.6; B1, lateral view; B2, plan view on the lower side of sclerite and its aperture. Scale bar 300 μm, except A3, 30 μm.

Fig. 1. Map showing location of sections 1, 3, Malaya Kuonamka River; 6, 7, Bol’shaya Kuonamka River.

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).

Fig. 3. Helcionellid mollusc Yochelcionella cf. Y. greenlandica Atkins and Peel, 2004 internal moulds from lower Cambrian Emyaksin Formation, Bol’shaya Kuonamka River, Anabar Uplift, Siberia; sample 7/36.7. A. SMNH Mo 160417; lateral (A 1, A5), sub-apical (A 2), upper (A 3), and supra-apical (A 4) views; A 6, polygonal texture on the surface of snorkel mould. B. SMNH Mo 160418; lateral (B 1), sub-apical (B 2), and upper (B 3) views; B 4, enlargement of B 2, with a shallow groove between the snorkel and aperture; B 5, apical part of the mould with tubercles; B 6, close-up of B 5. C. SMNH Mo 167648; lateral (C 1), sub-apical (C ), and upper (C ) views. D. SMNH Mo 167649; lateral view. Scale bar 600 μm, except A , 60 μm; B , 150 μm; B , 300 μm; B , 120 μm.