Friday, August 19, 2016

Gibbirhynchia amaltei brachiopod from France

This internal mold of a brachiopod is Gibbirhynchia amaltei from the Marginatus zone of the lower Jurassic (Pliensbachian). It comes from a site near Tournadous in the Aveyron region of southern France. The fossil looks like a Limonite replacement (or maybe lining) of the shell interior and retains just a small amount of the calcitic shell. The fossil is broadly ovate with valves that are mildly convex. When viewed from the front or back it looks somewhat flat or squat. Both valves have numerous and regular plications with a gentle fold and sulcus that is most evident along the anterior margins.

Brachial valve
Pedicle valve (note the cast of the channel where the pedicle muscle would have been)

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