Early Ordovician molluscs with preserved colour pattern from the Timan-Pechora Basin of Russia

Abstract

Unique preservation of the oldest colour pattern ( ≈ 490 Ma) of a molluscan shell and the first record of colour pattern in monoplacophorans are reported from a well that penetrated Early Ordovician strata in the Timan-Pechora Basin of Russia. The unusual preservation reflects low subsidence temperatures and minimal tectonic deformation. A colour pattern in the form of radial stripes coincides with the pattern of multiple muscle attachments to the shell, which obviously influenced the mantle margin responsible for the shell formation and pigment deposition. We assume that this type of colour pattern is one of the most ancient to have appeared in molluscan evolution.

Keywords::

• colour patterns
• Kirengella
• monoplacophoran molluscs
• Early Ordovician
• Timan-Pechora
• Russia

Acknowledgements

The authors thank S.N. Rozov (Novosibirsk) who supplied fossiliferous rock specimens, J.S. Peel (Uppsala) and A. Warén (Stockholm) for discussion, and H. Mutvei (Stockholm) and M. Calner (Lund) for their careful evaluation of the manuscript. All samples are stored in the Museum of Evolution, Uppsala, Sweden.