Sometimes you get a fossil with some added interest in the form of epibonts or odd growth patterns. This Pseudogarantina ammonite has something a little different, a pelecypod that was embedded it in during deposition or compaction of the sediments.
You only notice the pelecypod once you turn the ammonite around. I believe it's a species called Astarte minima based on the book "Sengenthal - Ein Eldorado für Fossiliensammler - Die Muscheln des Bajocium von Sengenthal" by Matthias Weissmueller from whom I also purchased this specimen from.
You can see that it was pushed into the ammonite shell by the current or waves during a storm. The ammonite shell itself may have been broken during a storm event or had just been exposed on seafloor for a while and was starting to break down.
I like that you can see the teeth along the edges of the pelecypod shell
The fossils found at Segenthal, Germany are found in rocks from the middle Jurassic (Bajocian stage). I purchased my fossils from Matthias Weissmueller's E-bay store.