Ceratoconus aff. striatus Chen and Zhang, 1980

Kouchinsky, Artem, Bengtson, Stefan, Landing, Ed, Steiner, Michael, Vendrasco, Michael & Ziegler, Karen, 2017, Terreneuvian stratigraphy and faunas from the Anabar Uplift, Siberia, Acta Palaeontologica Polonica 62 (2), pp. 311-440 : 355-357

Ceratoconus aff. striatus Chen and Zhang, 1980

Fig. 28 .

Material.—About 50 phosphatic internal moulds, including figured SMNH Mo Mo160413, 182307–182313, from samples 3/12, 3/12.2, K2/25, and K2/26 (section 3, Fig. 3), Medvezhya

Formation, western Anabar Uplift, Siberian Platform, Russia. Correlated with the uppermost Fortunian Stage.

Description.—Long narrow conical shell, curved up to 90º in one plane, with bulbous apex and rounded aperture. Protoconch not clearly separated from the rest of the shell. Inner shell surface (as replicated in internal moulds) with low transverse folds bent towards the apex on the convex margin of the conch ( Fig. 28B 1, C 1).

Remarks.—With its more rapidly expanding shell and a larger, more bulbous apex, Ceratoconus aff. striatus has a more robust habit than C. striatus .

Figures

Fig. 28. Mollusc Ceratoconus aff. striatus Chen and Zhang, 1980, internal moulds, from early Cambrian Medvezhya Formation, Kotuj River, western Anabar Uplift, Siberia, Russia; samples 3/12.2 (A–C, E), 3/12 (D), and K2/25 (F–H) from section 3. A–H. SMNH Mo182307–182313 (A–G respectively), SMNH Mo160413 (H) (compare H with Kouchinsky 2000a: fig. 7A–G). A1–D1, supra-apical; A2–D2, E–H, lateral; D3, subapical views; A3, apertural area with polygons enlarged. Scale bar 200 μm (A3), 500 μm (A1, A2, B–H).