Archive for October 6th, 2017

Wooster’s Fossil of the Week: A terebratulid brachiopod from the Upper Cretaceous of southwestern France

October 6th, 2017

Yes, we’ve had a run of French Cretaceous fossils here. This is because we’re in the midst of a major project stemming from summer fieldwork in the Type Campanian of southwestern France. The fossils are delicious, and they are before us every day in the lab.

The above terebratulid brachiopod was found by Macy Conrad (’18) at our Caillaud South locality in the Biron Formation. It is so beautifully symmetrical that it just had to be a Fossil of the Week. I’ve apparently felt this way before about terebratulid brachiopods since I’ve previously written about Triassic, Jurassic and Miocene examples before in this blog. A Cretaceous example at least completes the Mesozoic set.

The above view of our articulated specimen shows the fragmentary smooth dorsal valve of the terebratulid, with the posterior portion of the ventral valve extending upwards at the top. The ventral valve has the characteristic round pedicle opening.

This is the flip side showing only the exterior of the ventral valve. A bit of chalky matrix adheres in the lower left, and the darker circles at the top are a form of silicification called beekite rings.

Here is the side view of our terebratulid, with the dorsal valve on top and larger ventral valve below. You can see why brachiopods were given the common name “lamp shells” because of the resemble to a Roman oil lamp.

References:

Coquand, H. 1858. Description physique, géologique, paléontologique et minéralogique du département de la Charente. Besançon, Dodivers, 420 p.

Platel, J.-P. 1996. Stratigraphie, sédimentologie et évolution géodynamique de la plate-forme carbonatée du Crétacé supérieur du nord du basin d’Aquitaine. Géologie de la France 4: 33-58.