Ribbed Saddle-Oyster, Pododesmus patelliformis

Pododesmus patelliformis, also known as ribbed saddle-oyster, is a species of bivalve mollusk within the family Anomiidae. It can be found in the northeast Atlantic Ocean.

This oyster has a thin asymmetric shell up to 4 centimeters in length which is white, occasionally with brown markings. The outline is roughly circular and the beaks are central but set further back from the margin. The upper valve is sculptured with up to 60 weak radial riblets, and the inside is glossy white or tinged yellowish-green with two distinctive furrowed muscle scars on the upper valve. The lower valve is flat, thin, transparent, and hyaline and has one muscle scar.

Pododesmus patelliformis can be found on the northwest fringes of Europe extending from Norway to the Mediterranean Sea. It resides on coarse sand and gravel, attached to rocks or other shells by its byssus. It’s found in intertidal zones and down to around 200 feet.

Image Caption: Pododesmus patelliformis. Credit: Jan Johan ter Poorten/Wikipedia (CC BY-SA 3.0)