tombk Posted October 23, 2021 Share Posted October 23, 2021 I was collecting isorthoceras cephalopods at Graf Iowa (Elgin Member of the Maquoketa Formation, upper Ordovician). I found one partial specimen that in cross-section is about 8-9 times larger than any other I’ve found there. This first pic is from the field. (Don’t worry, the next photos have a scale cube in them!) The large specimen is about 8.9 cm by 5 cm. You can see cross sections of the usual-size isorthoceras in the rock (filled and infilled), and they’re closer to 1 cm across. Unfortunately, the specimen is fairly fragile. I’ve already had to glue together six pieces it fell apart into, and I haven’t been able to remove it from the matrix any further to get a better look at its sides. I’m wondering whether it’s an unusually large isorthoceras or a different animal altogether. Thoughts? Link to comment Share on other sites More sharing options...
connorp Posted October 23, 2021 Share Posted October 23, 2021 I don't see a siphuncle... Not sure what it is. Neat find. Link to comment Share on other sites More sharing options...
Al Dente Posted October 23, 2021 Share Posted October 23, 2021 It could be Endoceras. Endoceras, Spyroceras, and Beloitoceras are found in the same beds as the Isorthoceras. Link to comment Share on other sites More sharing options...
Tidgy's Dad Posted October 24, 2021 Share Posted October 24, 2021 Hate to say it, but maybe just a concretion...................... Life's Good! Tortoise Friend. Link to comment Share on other sites More sharing options...
Rockwood Posted October 24, 2021 Share Posted October 24, 2021 55 minutes ago, Tidgy's Dad said: Hate to say it, but maybe just a concretion...................... One would need to explain the other three similar shapes next to it. I would see that as a caution too. 1 Link to comment Share on other sites More sharing options...
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