Holes In Cephalopod

[Clanjones]

This cephalopod fossil (species unknown) has holes in its shell. It was submitted to the Science Museum of Minnesota's fossil ID program. The people there said that the holes were ornamentation on the shell of the cephalopod. However, I could not find information on a species of cephalopod that had holes in its shell like this. What does the Fossil Forum think the holes are?

There is also a round, smooth object on one end of the specimen.

Edited July 30, 2014 by Clanjones

[Auspex]

Actually, I'm not convinced it's a cephalopod...

[painshill]

Actually, I'm not convinced it's a cephalopod...

Yes... it looks more like a stigmaria (root cast). Anything more to see from an end-on view? Where exactly was it found?

Edited July 29, 2014 by painshill

[Pumpkinhead]

I remain skeptical as to wether or not that's a ceph also

[howard_l]

Do you know what age it is that would tell us a lot.

[Clanjones]

It was found in Cannon Falls and is presumed to be Ordovician in age.

[Ludwigia]

Based on that first photo I would tend to agree with my predecessors, but now that the second and third have appeared I'm starting to get confused. Perhaps that's a 2 in 1: Nautilus core inside, something else (plant?) on top. The two different sedimentary layers which can be clearly seen in the cross sections could support this assumption?

[John K]

It looks like it's possibly from the Shakopee Dolomites; definitely not plant material

the specimen looks very similar to cephalopods I've found in the general area from the same formation, sans "ornamentation"; the cross-section looks like the animal has been squashed a bit. I see a definite siphuncle

I wonder if they are pathological - evidence of predation/scavenging, perhaps?

[Tethys]

I see a definite siphuncle, but that is a very weird cephalopod. I collect from the Shakopee in the St. Croix river valley, but the cephs aren't black, they are usually the same color as the dolomite on the outside, chert on the inside, with pyrite in the suture lines. This fossil doesn't appear to have any shell material, but it is a cast of the inner surface of the shell. You can see the area that the shell once occupied as the narrow troughs on either side. It must have been ornamented similar to the Cretaceous Scaphites. The critter on the end could either be a Prasopora bryozoa, or one of the small round brachiopods. Crania?

[Pumpkinhead]

I don't buy this cephalopod theory. Even if it is a ceph, I don't see how the holes couldn't have interfered with the nautiloids internal buoyancy as they would have left gaps in the septal walls. I have never come across any nautiloids (or any kind of cephalopod for that matter) that have ornamental holes in them. I can see myself agreeing that it is a nautiloid given convincing diagnostic evidence, but I respectfully disagree with the ornamental hole theory. An alternative option could be that the nautiloid died of natural causes and once it sank to the sea floor it was scavenged upon by Gastropods. Gastropods nowadays have coarse tounges which they use to "drill" their way through the shells of their prey. Many recent examples of this can be found on bivalves from marine snails. I'm presuming that Ordovician Gastropods would have had similar feeding methods.

[wolf1]

Hi,

the holes in molluscs drilled by modern gastropods into shells (by their "radula") are exactly circular with a slightly slanting/oblique margin. Might be the holes seen above were deformed later on. I´ve seen a lot of these holes, but there was never more than one hole in a single shell. It doesn´t make sense to drill another hole when the animal inside the shell is already eaten.

Drill holes made by Euspira spec. in a shell of Euspira catena (da Costa). Kind regards: wolf

Edited July 31, 2014 by wolf1

[Pumpkinhead]

There could have been multiple Gastropods, and it would makes sense for the holes to deform over time. Or perhaps the shape of the holes created back then were different than what they are now.

[John K]

this cross section makes it look like the "holes" are really indentations

[Pumpkinhead]

They've been infilled, so it could be hard to tell wether or not they are indentations or holes unless someone cleaned them out

[Plax]

perhaps the layer removed (buy nature) from the top of the crushed ceph was coarsely conglomeratic leaving deep smooth indentations in the fossil during the crushing and deformation phase, if we weren't looking at the first pic with its mineral stain enhancement no one would argue that this wasn't a cephalopod (I think)

[Auspex]

The edges of the indentations do not show a broken edge (as I would expect from damage to a brittle shell), but are smoothly chamfered.

[Pumpkinhead]

If the infilled holes were cleaned out we might be able to see its septa which would cinch it in my opinion. The only object of debate after that would be the origin of the holes. How was it found? Are there many glacial striations around the area where you found the fossil or any other visible examples of erosion of the rock?

[BobWill]

The 1st picture seems to have more matrix still attached than the others. Could we see a picture of the bottom now that it's free from the rock? Also you mentioned a round object on one end but it appears on both ends, and with a smaller round object in the center on one end. If this was identified as a cephalopod maybe they were talking about just the round object and the smaller round object is the siphuncle. There is probably not enough evidence to confirm that ID and it still doesn't tell us what the darker part is.

Edited July 31, 2014 by BobWill

[Clanjones]

This fossil itself was not directly eroded by glaciers. It was split out of the middle of a cliffside. How would you guys recommend cleaning out the indentations?

[Auspex]

There are cephalopod features within the matrix which may not have anything to do with the surfacial feature and its holes:

[Ludwigia]

There are cephalopod features within the matrix which may not have anything to do with the surfacial feature and its holes:

~.JPG

That's about the way I see it too including the question marks.

[Pumpkinhead]

So you're saying that the white thing in the middle is the nautiloid and that the dark object is something else?

[Tethys]

Fossils in the the lower Ordovician in Minnesota are frequently preserved as casts and molds. Rarely are entire cephalopod shells preserved. You usually find just the cross section that was within a narrow band of sediment, with anything above or below that not preserved at all. My take is that the grey center section is chert fill. The small quartz filled hole is the siphuncle. There is nothing left of the shell itself. We have a lot of unusual mollusks, and unusual forms of preservation from the late Cambrian and well into the Ordovician. Here is my favorite mollusk cast. Photos are top view, side view to show the sinuous groove, and two views of the radula preserved as an imprint.

[BobWill]

So you're saying that the white thing in the middle is the nautiloid and that the dark object is something else?

Yes. I'm saying that's what the folks at the museum may have been referring to as a cephalopod since the dark surface with the dents shows no resemblance to one.

[Pumpkinhead]

I could agree with that