Jump to content

Large cephalopod from Graf


tombk

Recommended Posts

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!)

IMG_0515.thumb.jpg.ede14d2ae26ec66379fce45bbd92c027.jpg


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. 

IMG_0530.thumb.jpg.6c53c5fbbbc05d7095154fb6c31df54c.jpg

IMG_0534.thumb.jpg.808a416c268d0321d679431164ef4e09.jpg


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 post
Share on other sites

It could be Endoceras. Endoceras, Spyroceras, and Beloitoceras are found in the same beds as the Isorthoceras.

 

 

37460CAD-604A-46B7-BFC2-93248E6F7A71.jpeg

24155E5E-2808-4592-A81C-6735FE92432B.jpeg

  • Learned something new 1
Link to post
Share on other sites

Hate to say it, but maybe just a concretion......................

Link to post
Share on other sites
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.

  • I Agree 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...