Mollusk in a phosphatic concretion

[Missourian]

Phosphatic concretion, Muncie Creek Shale, Kasimovian/Missourian Stage, Pennsylvanian

Kansas City metro, KS/MO, USA

 

I'm pretty sure this is a mollusk. The fine striations remind me of those on some Poterioceras:

 

 

 

Any ideas?

[Bullsnake]

I would have thought (crushed/flattened?) Conulariid by the striations.

I've found similar in the Muncie Creek I assumed conularia...now you have me re-thinking!

So, in googling, I came across this old TFF thread and wonder if there's any connection.

 

 

 

[Missourian]

2 hours ago, Bullsnake said:

I would have thought (crushed/flattened?) Conulariid by the striations.

I've found similar in the Muncie Creek I assumed conularia...now you have me re-thinking!

So, in googling, I came across this old TFF thread and wonder if there's any connection.

 

I had thought it was a conularid until I noticed the yellowish thick shell on the left end of my specimen.

 

I've seen a few illustrations of Poterioceras that have a somewhat similar shape. Just today, I found this old (1903) illustration of several Poterioceras sauridens from the Silurian (I think):

 

 

In any case, I don't really have a good handle on the range of forms of Pennsylvanian Poterioceras. I'm guessing this is due to preservation and shell forms at various growth stages.

[cngodles]

Poterioceras has had a bit of a rough go. I'm writing passages for many cephalopods, including Poterioceras curtum (Meek & Worthen, 1860) for a book I'm putting together, but I'll quote the text below. Essentially, at the time of the Treatise publication, authors were certain these were the adult part of Brachycycloceras. Yet, years later, it was proven not true.

 

Quote

This breviconic cephalopod species first rose as Cyrtoceras curtum (Meek, 1860). Later, authors declared it to be the adult stage of Brachycycloceras (Furnish et al., 1962), as published in the Treatise of Invertebrate Paleontology (1964, Part K Mollusca 3, Furnish and Glenister). Researchers at the time considered today’s Brachycycloceras to be the deciduous portion of a larger conch, a cephalopod formerly and currently known as Poterioceras. Much later, new evidence and research redivided the names (Windle, 1973), prompting Niko and Mapes (2009, 2010) to redescribe species of Brachycycloceras.

 

I started finding Poterioceras curtum this year. I have about six specimens, and two that are full-size like the ones below.

 

Here is a great specimen I found from the Kasimovian before I reassembled it.

 

 

And here is the same specimen, put (paraloid) back together and flipped over.

 

 

Yours sort of looks like one, perhaps an early juvenile. It has the breviconic shape.

 

I hope that helps. There is not much new published about these, that I can find.

 

 

 

[cngodles]

And some exceptional specimens from a much older post.

 

 

[Rockhound Ryan]

Oh that's so cool, it looks like the softer parts of the animal have been replaced by baryte or calcite. Likely it left a void in the sedement which was filled over time with mineral from hydrothermal activity. Very interesting