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I found this ammonite segment a while back in SE Johnson County in an area that is right near the Edwards Formation that is adjoined by a complex area that has Duck Creek and Ft. Worth limestone to name a few mixed in. I tend to think it may have been the complex formation, but I couldn’t tell you what part of it. I found it on top of the ground after a road was put in for a new house being built near some property I own out in the country.


It is a segment of an ammonite. It weighs about 10 pounds I’d say. Is about 8 inches long and 6 inches tall or thick. Can anyone tell me about what large ammonites might be in that area?



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I have a few large segments, but I’m pretty sure one of them is of a very different species than this one. 



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2 hours ago, NSRhunter said:

Section of a large Eopachydiscus ammonite :) 

I know experience counts for a lot in IDing stuff.  Could you please educate me as to what you based this specific ID upon. 

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Now that’s a biggun! I’ve held in my hand ammos a few millimeters across, amazes me the size range of these critters!

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Uncle Siphuncle

Eos were quite prolific, and the basal Duck Creek fm is quite persistant wherever Kdc is mapped, so you bump into this species often in TX.  I’ve taken them from Oklahoma to far West TX.


They are readily distinguished by large size and lack of surface ornamentation except for perhaps broad constrictions on adult whorls.  


Common fossils in the same zone include 6-10 inch Inoceramus clams, echinoids Macraster washitae and M. elegans, as well as Mortoniceras and Idiohamites ammos.  I’m rather keen on the scant shark and fish matl that also turns up in the same zone.  Bob Williams can speak to that fauna.

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