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David in Japan

Santonian Bivalve ID (probably veneridae)

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David in Japan

Hi everyone, 

It's been a while. Here are two picture of a bivalve I found in Himenoura formation Japan.

I have been hunting these place regularly for 2 years but it is the first time I found such large bivale there.

 

I looked into my local documentation to put a name on it but I didn't found anything.

 

Here is some information about the beast:

Formation: Himenoura

Age: late Cretaceous, santonian

size: 13cm long / 9cm width

 

I think it is a kind of veneridae because the hinge teeth (even if difficult to see on the picture and worn) looks like Mercenaria mercenaria teeth.

 

If someone have any idea about the clam shell, I would be gratefull to hear about.

 

20161113_203123_001.jpg

 

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David in Japan

20161113_203106.jpg

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fossiling

Looks like acrosterigma.

Let's see others' opinion !

 

1479039524919.jpg

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tmaier

The prominent umbo and fairly close bilateral symmetry makes it look like it is in the cockle family. But then it seems to also be pretty thick and have a smooth outer surface... not like something in the cockle family. I don't see the hinge teeth, they seem to be under some matrix or broken away, so that is not a help.

Venus shells can have a thick shell and smooth outer surface, but then they often are not nicely symetrical and normally don't have such a large umbo. A Mercenaria clam like you mention is a Venus.

So this seems to be half Venus and half Cockle (half Veneridae and half Cardiidae). That makes us back up the taxonomy tree and say it is in the the order Veneroida, but according to Wikipedia, the cockles have been thrown out of that order.

Mmmm... this one is confusing.


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abyssunder

Although I'm not familiar with Japan, from what I have read the Upper Cretaceous Himenoura is a Group of formations, for example in the eastern part of the Amakusa - Kamishima Island, where it is exposed, it is devided into the Hinoshima and Amura Formations (Santonian - Campanian) - according to  Yuki Kojo et al. 2011. Stratigraphy and detailed age of the Upper Cretaceous Himenoura Group in the eastern part of Amakusa - Kamishima Island, Kumamoto, Japan. Jour. Geol. Soc. Japan, Vol. 117, No 7, p.398-416. pdf

 

Compared the data from the mentioned document with your specimen, I think that could be an inoceramid, like Sphenoceramus.

 

1.jpg

 

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David in Japan

Thank you Abyssunder,

 

The inoceramid that could a "little bit" looks like to this shell would be Inoceramus higoensis or Sphenoceramus elegans pseudosulcatus but they are still pretty different.

I don't want to put away the inoceramid but I don't think it is one.

 

Picture with an Inoceramus higoensis fragment

 

20161113_225118.jpg

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abyssunder

The variants for Inoceramus might be : Inoceramus (Inoceramus), Inoceramus (Sphenoceramus), Inoceramus (Mytiloides), Imceramus (Retroceramus), Inoceramus (Mytiloceramus), Inoceramus (Cataceramus).
You may need this document : I. Hayami. 1975. A systematic survey of the Mesozoic Bivalvia from Japan. The University Museum, The University of Tokyo, Bulletin (10) Here

 

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David in Japan

Arg, I waited too long before looking at the link you shared Abyssunder. the link is dead now.

 

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abyssunder

You're right, the link is dead. That is a good reference, unfortunately was not a downloadable document...wait, maybe is just a server problem. :(

In this moment the link is working. :)

Edited by abyssunder
Update

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David in Japan

Thank you very much to all of you for helping me to ID this fossil.

 

Just a short message to say that I had been able to put a name on the shell thank to the help of the professor Masayuki Tashiro.

 

It is a thorny oyster called Spondylus pseudocalcaratus.

 

Here a link for those who want to have further information concerning this fossil (page 61) and bivalve yielded by the Himenoura formation.

 

http://www.palaeo-soc-japan.jp/download/SP/SP19.pdf

 

 

 

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abyssunder

The first thing that caught my eye was those spiny shapes visible on the surface of the specimen. I thought it could be Spondylus, but I excluded this because of the very large dimensions. Your specimen is almost double in size compared to the usual ones, also compared with the dimensions presented by Masayuki TASHIRO in BIVALVE FAUNAS OF THE CRETACEOUS HIMENOURA GROUP IN KYUSHU.

 

Measurements (in mm):-
Specimens                               Length        Height     Thickness
KE 2115, left valve                     70.0            65.0         10.0
KE 2116, left valve                     56.0            54.0
KE 2117, left external mould       23.5            23.0           3.0
KE 2118, left internal mould        20.0            18.5
KE 2119, left external mould       52.0            48.0           7.0
KE 2120, right external mould     45.0+          38.5         20.0

 

0002.jpg

0001.jpg

 

It's a good document. Thanks for sharing. :)

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David in Japan

Yes he told me that it was one of the biggest he ever seen. this formation is so exciting, so much to discover.

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