Need help ID strange patterns and trilobite

[PaleoOrdo]

During my last visit at Bødalen, I found my second trilobite at the location, similar to the first one presented at this forum, mid-Ordovician and probable in the Ptero elegans zone. In the same stone there is also several puzzling forms, among them circular patterns. Anyone have an idea what these are?

The length of the bigger oval or circular pattern is about 4-5 cm, that is the longer side.

 

 

[PaleoOrdo]

More enlarged pictures:

In the next picture one can see several things, and patterns which may or may not belong to the trilobite?

 

[grandpa]

Largest item is a portion of a bivalve, I believe.  Can't make out enough detail on the smaller items to offer an opinion on them.

[PaleoOrdo]

Next, patterns in another part of the stone:

And, finally, a close up on the trilobite:

[PaleoOrdo]

Thank you for your opinion, Grandpa. You may be right, but I wonder if it is possible that it is the underlayer of a trilobite, similar as seen in this specimen which I found at another location (presented before at this forum). Notice the densed packed lines in the lower and right part of this picture:

[PaleoOrdo]

Here is a better picture of the structure:

[Fossildude19]

I agree it's a bivalve.

There is definitely a partial pygidium as well, but the other item  is too blurry to tell. 

[PaleoOrdo]

Ok, I think you are right, the lines are not bended enough at the end to belong to a trilobite.

I tried to edit and make the pictures more clear, but the surface is inherently unclear. Thank you both for your help!

[Kane]

1 hour ago, PaleoOrdo said:

Thank you for your opinion, Grandpa. You may be right, but I wonder if it is possible that it is the underlayer of a trilobite, similar as seen in this specimen which I found at another location (presented before at this forum). Notice the densed packed lines in the lower and right part of this picture:

The finely ribbed portion of the trilobite would be the impression of the doublure. 

[PaleoOrdo]

Thanks, Kane. I tried to google to get some info on doublure, but I m not sure I understand preciesly what it means. Is it the continuous underlyer of internal tissue under the exoskeleton or the impression of the exoskeleton on the tissue?

[Fossildude19]

It is the exoskeleton that covers the underneath of the trilobite. The texture is part of the exoskeleton material.

[PaleoOrdo]

Thank you for the information Tim.

I also found a fossil in what I believe is Late Ordovician in Lunner area, in a road cut North of Oslo, but it could also be early Silur because the geological map is not so clear as to the border between the two locations. Is this a trilobite or some other animal?

A more close up photo:

[Top Trilo]

Looks a lot like a soda can tab,

 

[Top Trilo]

It could possibly be an agnostid trilobite, appears to have the large cephalon and pygdium with few segments

[PaleoOrdo]

Thanks for the reply. It looks similar yes. The Cephalon looks however bigger than the pygdium in your picture? Is it seen from the underside or above?

[Kane]

If the material is Silurian, it would not be an agnostid. The morphology does not seem right for trilobite. I would guess two conspicuously situated and abraded brachiopod steinkerns with some third specimen (piece of gastropod?) making up the centre. 

[PaleoOrdo]

It is hard for me to see a gastropod in the center. Which kind of gastropod could that be? The whole structure also is placed in a nice symmetrical pattern. But I also had and have strong doubt that it is a trilobite. When I checked the geological map, it seemed to be within the ordovician zone (Katian), but I am not abolutely sure.

[Kane]

14 minutes ago, PaleoOrdo said:

It is hard for me to see a gastropod in the center. Which kind of gastropod could that be? The whole structure also is placed in a nice symmetrical pattern. But I also had and have strong doubt that it is a trilobite. When I checked the geological map, it seemed to be within the ordovician zone (Katian), but I am not abolutely sure.

I am seeing curvature, but there is only one image and no measurement to base any guesses on. The three distinct areas could also be one cross section of gastropod whorl, but we'll need more information. 

[FossilDAWG]

It is a section through a coiled nautiloid.  I say a nautiloid rather than a gastropod because it looks like there is a surface of the septum, and the siphuncle is visible, in the inner whorls.

 

Don

[Kane]

I agree with Don. 

[PaleoOrdo]

The discussion is very interesting. Are there any pictures to compare with of the species or genus of nautiloid you are talking about Don? 

The speciemen is about 5-7 cm long (I have it outside the house and it is very cold for me to go out find it right now to measure it precisely, but I can do if you wish).

[Caverat]

37 minutes ago, FossilDAWG said:

It is a section through a coiled nautiloid.  I say a nautiloid rather than a gastropod because it looks like there is a surface of the septum, and the siphuncle is visible, in the inner whorls.

 

Don

Also agree with Don.

[FossilDAWG]

Unfortunately we cannot see several diagnostic characters for the genus or species with this sort of a view.  We can see the whorl profile and degree of involution (how much later whorls overlap the inner ones) but we cannot see the suture line, shell ornament (ribs/nodes/spines if any), or shape of the aperture.  If you know the correct geological formation and horizon or member, you might be able to make a reasonable "guess" based on published data on the cephalopod fauna, as long as it is not too diverse.

 

Don

[PaleoOrdo]

I understand, thank you very much for the information Don!

[PaleoOrdo]

Did I understand right, that is is only the middle part wich is the nautiloid (and only a part iof it), the two other parts something else like brachiopods?