What is that stain ?

[fifbrindacier]

Hi everybody. In my collection i have some fossils i inherited a few years ago. In those ones i have that little goniolina hexagona from the Kimmeridgian of Angoulins sur mer, in the department of Charentes-Maritimes.
I always wondered what could be that stain behind the Goniolina (behind the left side of it on the first photo).
It looks like some kind of phoronid but could also be mineral.

Regards, Sophie.

[fifbrindacier]

I must precise that the stain is about 1,5 centimeters long.

[Edited by fifbrindacier on 14-10-2017 at 16:39 GMT +1]

[FossilDude]

I am sorry Sophie, I have no idea what this stain could be... These kind of things are often very difficult. Perhaps it is 'something' fossil, perhaps it is not.

cheers,
Johan

[KoenJ]

Hi! I think it's a serpulid seen from below. You see it from the point where it used to be attached to the shell.

In the Dutch-Belgian cretaceous they're quite common in sea urchins, oisters and the remains of aragonitic bivalves and gastropodes.

[Bewerkt door KoenJ op 18-10-2017 om 18:04 NL]

[fifbrindacier]

I thought you might be right, my supposition of phoronid comes from that funny stain at the top of it, with those two points in the alignment of each half part of the rest of the stain (you can see some "kind" of vertical separation on it).
In fact, if you look well, it seems that the Goniolina and this are on a deteriored shell of gasteropod.

Regards,
Sophie.

[Edited by fifbrindacier on 19-10-2017 at 18:17 GMT +1]

[Edited by fifbrindacier on 19-10-2017 at 18:18 GMT +1]