Plectronocerids and other neat nautiloid fossils

cambrian cephs

Update. Yes here they are. Some plectronocerid, cambrian cephalopods.

The one triangular larger one on the right, I believe, is a palaeoceras. The white portion is just over one inch in length. The rock and lichen did interesting effects that made these pop out a bit. The chambers clearly got more filled with calcite, which apparently these lichen don't like (liche?). And these are left uncovered. Other chambers closer to the end and the living chamber filled with the surrounding matrix and got more degraded and colonized. One can see a faint outline of the wall of the living chamber on the palaeoceras.

The one somewhat large sliver of white, with a second sliver of white to the left of the palaeoceras along with the faint outline in the matrix there, I believe is a plectronoceras.

There's a small sort of very small slender fellow below the one on the right, which may be a balkoceras, or one of the not-quite-cephalopods that also happened at the end of the cambrian. Ones with chambers but no siphuncle.


Only cephalopod order left to find is intejocerida. Like Rossoceras Any suggestions?
 

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willsquish;140635 said:
Update. Yes here they are. Some plectronocerid, cambrian cephalopods.

Nice fossils :smile: Can you see any signs of the septa, or are they too thin? Are there a few trilobite parts floating around on that rock, or are they brachiopods?

willsquish;140635 said:
Only cephalopod order left to find is intejocerida. Like Rossoceras Any suggestions?

In the Juab Formation around Fossil Mountain, in the Southern Confusion Range, Utah, Rossoceras is fairly common. :cool2:
 
Architeuthoceras;140650 said:
Nice fossils :smile: Can you see any signs of the septa, or are they too thin? Are there a few trilobite parts floating around on that rock, or are they brachiopods?

The septa are fairly faint on this, but when wet, they can be seen. In the pic you can see some very faint ones from shadows on the calcified portion, and from the shadows in the matrix. Another specimen which seems to have mostly balkoceras has more visible septae. There are some gastropod curls in this rock, as well as some brachiopods. There is at least a pygidium I see on the block I've not photographed yet which has primarily balkoceras (and/or possibly kygmaeoceras, still working it out). And some other trilobite bits on rocks from the same location as this piece, a bit lower down.

Rossoceras is common? Know anyone who might trade? The road trips, while fun and adventurous, take awhile to save up time to go on, with research as it is.
 
A few more plectronocerids

Hello,
Here are a few more from the same area, but a different locale. The geological map had it prehaps as the member just below the san saba member, but it was a quarry, so some stone might have been from a layer above. Hard to say. But they do look cephalopody. The first two are the same under different light. The last two are dry and wet.
 

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Plectronocerids

Here are a few things from the original locale. Broke some open to find them. There's also a trilobite tail found in one of the rocks of the same member. Dry and normally lit vs wet and brightly lit for the first two.
 

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Last plectronoceras for now

Here's the last of the ones I've found so far, more or less. The second pic has lines I see with a loupe and better light drawn in.
 

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Polishing would help.

Here's a couple of much younger ones in polished section - Moroccan orthocerid showing detail of septal necks and siphuncle and a Carboniferous actinoceratid.
 

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Yes, polishing would help, unfortunately it would also probably destroy the fossil. So if it is being done for a taxonomic or other study where these fossils and the preparation process could be documented step by step, I would say go for it, otherwise a diagram or some means of non-destructive preparation will do. I have seen a few examples of fossils in the literature where the only remaining view of a surface is in a photo, the original ground and polished away, never to be seen again. :sad:
 
yeah, there's one or two I might try polishing, like the one pictured to the left of the trilobite tail, due to the fact that a, its negative is already in the other piece of rock I have, and b, it's got a really crummy surface. But as Kevin said, these are at the most like 3 to 5 mm thick specimens, so most probably wouldn't work well. The 2 palaeoceras' I saw in the actual paper were just a small section out of matrix that had been polished by erosion. other specimens of cephs from the area, they had to rub white powder in and wipe off to get white lines where depressions were, or used high light angles. I could try that sometime. I'm grateful to the lichens for doing similarly to my first specimen there. I should try a different angle photo of it. The gray septal lines on the not quite fully calcified parts of the palaeoceras show up ok with a loupe.

Here's one with a flash that sort of shows that.
 

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