Hyolithida, Sysoev, 1957

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 : 455

Hyolithida sp. indet. 1

Fig. 25A .

Material.—Over twenty internal moulds, including SMNH X 4656, from sample 7/36.7 and several additional moulds from samples 7/54 and 7/55. Emyaksin Formation, Bol’shaya Kuonamka River; correlated with the Delgadella anabara and Judomia zones, Atdabanian Stage.

Description.—Conch slightly dorso-ventrally curved, with convex, arched dorsal and slightly convex ventral sides and lateral longitudinal ridge between them. Cross-section is rounded triangular. The aperture has a slight dorsal sinus and a protruding prominent ventral lip. Shallow dorsal sinus just inside aperture. Apical angle ca. 20º.

Figures

Fig. 25. Hyolith conchs from lower Cambrian Emyaksin Formation, Bol’shaya Kuonamka River, Anabar Uplift, Siberia; sample 7/36.7. A. Hyolithida sp. indet. 1, SMNH X 4656; lateral (A1), dorsal (A2), and apertural (A3) views. B. “Lenatheca groenlandica (Poulsen, 1932)”?, initial part, SMNH X 4640; apertural (B1), dorsal (B2), and lateral (B3) views. C. Microcornus? sp., SMNH X 4655; lateral (C1), apertural (C2), and dorsal (C3) views. D. Loculitheca? sp., SMNH X 4634; D1, oblique apical view, septum; D2, plan view of the conch. E–G. Conotheca cf. C. mammilata Missarzhevsky in Rozanov et al., 1969. E. SMNH X 4625; lateral view. F. SMNH X 4626; dorsal view. G. SMNH X 4627; lateral view. Scale bar 600 μm.