Lucinid bivalves - Miocene of the Styrian Basin, Austria

[FranzBernhard]

Hello,

 

again a question from the Styrian Basin of Austria. I think these are three lucinid bivalves. They are middle miocene in age (ca. 15 Ma) and come from the "Florianer Schichten" of the Styrian basin in Austria.

I don´t think that they are Loripes dujardini (= Lucina dujardini), but that is the closesd match compared with the bivalves in Hörnes (1870). They also resemble in many aspects Linga columbella, but the bivalves in question are much flatter. They are associated with "true" Linga columbella, Divaricella ornata and Codakia leonina and various molluscs ("Tellina", Callista, Athleta, Amalda and much more). Size is 13 mm each.

 

Thank you very much for your suggestion!

Franz Bernhard

[FranzBernhard]

New thoughts: Could these be juvenile Linga columbella?

About the wide/thickness-ratio:

Wide     Thickness    W/T-Ratio

Three examples above:

13.5        4.5-5            2.7-3

The two "true" L.c. from the same locality:

14-15      9-11             1.4-1.6

However, the abundant L.c. from nearby localities have these measurements:

16.5-20   7.5-10           2-2.2

Which is close to the typical sphaerical appearance of L.c.

 

Any thoughts?

Best regards and thank you!
Franz Bernhard

[abyssunder]

How did Hornes distinguished them in his work, or what is the difference between Lucina columbella and Lucina dujardini?

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The beak is more prominent and curved in L. columbella than in L. dujardini.

here is a specimen registered in MNHN ( MNHN.F.J14456 ) to see the difference:

 

link to source

 

Also, in Harzhauser et al., 2013 is stated that: " Lucina columbella is easily identified from other Lucinidae by its almost circular, strongly globose shell with a large, distinct lunule and a broad area, which is set off from the main shell portion by a deep a relatively deep radial sulcus, and extends over ca 20% of the total shell surface. The shell is ornamented with regular commarginal ribs. "

 

[FranzBernhard]

Hello abyssunder,

 

thank you very much for your help, the photo and the link to the paper. The beak of the bivalves in question is clearly not that of L. dujardini. (Very good that the specimen on you photo is nearly the same size as the bivalves in question!).

 

For L. dujardini, Hörnes writes: "Shell nearly circular, compressed, nearly flat; surface is covered with fine, concentric growh rings. Lunula small. Two lateral teeth, well developed, especially the frontal one. Rim is smooth."

 

Except the bivalves in question are "small" (13 mm vs. 20-22 mm) and a bit flatter than usual, every other aspect speaks for (juvenile) L. columbella.

 

Thanks again!
Franz Bernhard