Orthothecida, Marek, 1966

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 : 451

Orthothecida ? sp. indet. 2

Fig. 26I, J.

Material.—Ten internal moulds, including SMNH X 4644 and 4645, from sample 7/70 and eight from sample K1-3B; uppermost Emyaksin Formation, Bol’shaya Kuonamka and Malaya Kuonamka rivers (respectively); Calodiscus -Erbiella Zone, lower Botoman Stage. Several internal moulds from sample 7/54; Emyaksin Formation, Bol’shaya Kuonamka River; correlated with the Judomia Zone , upper Atdabanian Stage.

Description.—Conchs, 2–4 mm long, slightly curved dorso-ventrally, with apical angle ca. 10º. Initial part gradually narrows towards the apex (Fig. 26J). Cross-section rounded triangular (Fig. 26I 3, I 4). Apertural part expands in a funnel-like fashion. Surface of internal mould is smooth, covered with faint discontinuous transversal striae.