What could have left these marks?

[Alexander D.G]

Hi everyone,

 

Found this gryphaea a while ago and have been pondering about what could have left these marks on this fossil, anybody want to take a crack at what it could be?

 

I had at first assumed that they were modern marks left by a tool of a fellow fossil collector but as can be seen in the first picture the shell 'bends' into the marks, which can only have happend while the shell was still growing. Thoughts?

 

Some general info:

- Location found: Vaches Noires

- Age: ~150 million years old

 

- Fotos:

[Ludwigia]

Might be percussion marks.

[Mark Kmiecik]

They look recent to me.

[Alexander D.G]

3 hours ago, Mark Kmiecik said:

They look recent to me.

If it were then why would the shell seem to have grown around the crack? If it were recent I would expect the lines of the shell to be continues, instead of the more M shape it has now with the crack in the middle.

 

Edited June 28, 2023 by Alexander D.G
Typo

[Kane]

Maybe it got tumbled along some rocks prior to fossilization 

[Alexander D.G]

4 hours ago, Ludwigia said:

percussion marks

New to this terminology. If I understand it right you theorize that shell got hit by rocks either pre or post fossilisation?

[Ludwigia]

36 minutes ago, Alexander D.G said:

New to this terminology. If I understand it right you theorize that shell got hit by rocks either pre or post fossilisation?

yup

[ynot]

5 hours ago, Ludwigia said:

Might be percussion marks.

 

4 hours ago, Mark Kmiecik said:

They look recent to me.

 

1 hour ago, Alexander D.G said:

If it were then why would the shell seem to have grown around the crack? If it were recent I would expect the lines of the shell to be continues, instead of the more M shape it has now with the crack in the middle.

 

 

I have to go with growth interruption, either by damage or blockage. The normal growth lines before the marks and the deformed lines in line with and after the marks could not happen after the animal died - pre or post fossilization.