Arietite ammonite, France (Burgundy, Côte-d'Or, Semur-en-Auxois), Lower Jurassic, Lias, Lower Sinemurian (~189 to 196 million years ago), diam. 50 cm approx.

Symbolic stage of Burgundy, the Sinemurian consists of alternating clay and compact, thick and very hard limestone. It is almost impossible to find large ammonite specimens in Burgundy except in the case of major works or earthworks.