This structure is not rare in mid-Miocene shallow water samples, associated with bryozoans and segrass-related molluscs - all specimens are very homogeneous in outline and shape.
I would say molluscs, but the answer would not be so easy, I supposed. Otherwise you will not asking, aren't you?
But the microstructures on shell anyway show high similarity with mollusc skeletons. How the cross section of the shell looks like?
What about two different animals, one gastropod (1c) and the second parasitic bivalve? Anyway interesting found, I didn’t see such fragments in my samples…
Hi Mathias,
one possibility (not a certainty) is that they are accessory plates of pholadid bivalves. There are several types (protoplax, mesoplax, metaplax, callum/callus), some are paired and mirror-images of each other, others are single and bilaterally symmetric. In some species an individual has multiple plates of different types, in other species only one or one pair.
Which is the chemistry composition of their shells? Are they calcitic? If it is shells!!!
Hi Mathias,
These look very pholadid. Maybe not the accessory plates as Enrico suggested, but more likely the broken-off apophyses from inside the valves?
Hi Mathias - I don't thik to be one mollusck, mabye, (but maybe) it could be something sckeleton part of arcaic Cyrripedia (Lepadomorpha s.l.). I send to you an important work maybe it could help you.
Cordially Gianluigi
Microstructures on shells show good correlation with mollusc skeletons. But I'm not sure!
1C is not an Ostracoda, because do not have the typical hinge neither other internal structures as muscle scars, etc
Dear All,
thanx for the many responses. It turned out to be the apophysis of a pholadid bivalve!
mathias
Hi Mathias,
I just stumbled upon your question (also forwarded to me by Steve Tracey for unknown reasons) and do not believe that these fragments are apophyses of a pholadid bivalve.
I found such fragments in mica clay deposits of middle Miocene age (Reinbekian) in Twistringen (NW Germany), where they are excellently preserved (still glossy). I have always considered these to be fragments of the right valve of Heteranomia squamula (Linné, 1758), the part on the right-hand side next to the byssus hole (seen from inside). One clearly sees the ridge (crus) and on the outside, just on top of the ligament (your fig. 1c !) one can recognize the prodissoconch.
I am sorry for the quality of the attached pictures - I don't have proper equipment at my disposal now. I also add a picture of two specimens from the Karaman basin.
Looking forward to your reaction with the greatest interest.
Jaap van der Voort
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