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Pecan gap chalk nautiloid?


Rayminazzi

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Nice find! It is not a nautiloid but a gastropod, possibly Gyrodes sp. or something similar to it. A nautiloid steinkern (cast) such as your's would have straight sutures. 

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I can tell you it is not a Pachydiscus.

 

May we see the aperture? It is the mouth or opening of the shell. If it is a cephalopod and the whorl shape is preserved that will help us have a better idea of what it is. May we also have something for scale?

 

To my knowledge there are no nautili reported in the Pecan Gap, but that doesn’t mean they aren’t there. The Ozan has had these reported in it:

576B85BF-7CDF-4B8D-BCC3-F746BD61E981.thumb.jpeg.4e0b8a914a91bfc2bf930a11695c6172.jpeg

This is the Eutrephoceras dekayi from the Ozan.

9370F93C-8015-480A-BC20-73275AFF4D1D.thumb.jpeg.e35028e0ec448b2f88a2cc88a90191f2.jpeg

 

There is a line on the outside edge almost in the center. Does that look like a siphuncle? If so it cannot be a nautilus. Their siphuncle is internalized.

 

There is a gastropod I have found which is somewhat similar, but the center isn’t recessed like that.

 

Kim

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1 hour ago, PFOOLEY said:

Interesting. So apparently Pecan Gap nautiluses don’t necessarily show sutures, similar to Austin Chalk nautilus preservation. Not so sure now, but if I am looking at the pictures right it still looks more like a gastropod to me. 

 

Could we get a few close-ups of the center?

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Kpg nautiloids tend to be rather nondescript and compressed, often on funky angles.  From what I can make out on my phone, this one is better than most. 

Grüße,

Daniel A. Wöhr aus Südtexas

"To the motivated go the spoils."

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1 hour ago, Uncle Siphuncle said:

Kpg nautiloids tend to be rather nondescript and compressed, often on funky angles.  From what I can make out on my phone, this one is better than most. 

So are you leaning towards nautilus rather than gastropod?

I’m up in the air. How wide the whorl is makes me think gastropod, but the center makes me think cephalopod. I have seen gastropods with the top, center knocked out, but the whorls around the center in those cases are very thin and fine.

 

I think the detail necessary for determining the class of mollusk it is is missing.

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2 hours ago, Rayminazzi said:

Different place but same formation, found this today.

IMG_20181014_102323.jpg

IMG_20181014_112145.jpg

Nice Pachydiscus travisi.  Most always compressed in the local Kpg.

Grüße,

Daniel A. Wöhr aus Südtexas

"To the motivated go the spoils."

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4 hours ago, KimTexan said:

So are you leaning towards nautilus rather than gastropod?

I’m up in the air. How wide the whorl is makes me think gastropod, but the center makes me think cephalopod. I have seen gastropods with the top, center knocked out, but the whorls around the center in those cases are very thin and fine.

 

I think the detail necessary for determining the class of mollusk it is is missing.

Having not seen it in person, I’d hedge toward nautiloid at this point.  The Kpg seems to preserve them in the most nondescript fashion of all Texas formations I’ve hunted. 

Grüße,

Daniel A. Wöhr aus Südtexas

"To the motivated go the spoils."

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