Norki Posted July 7, 2020 Share Posted July 7, 2020 Hello all, I recently found this strange fossil within a sandstone concretion from the late Campanian marine Bearpaw formation. I'm very familiar with the typical ammonites and other molluscs of the formation, and haven't seen anything like this - is it some sort of nautiloid, or something else entirely? Thanks. 3 Link to comment Share on other sites More sharing options...
LordTrilobite Posted July 7, 2020 Share Posted July 7, 2020 I'd say some type of nautiloid sounds about right. 2 Olof Moleman AKA Lord Trilobite Link to comment Share on other sites More sharing options...
Norki Posted July 7, 2020 Author Share Posted July 7, 2020 It does seem to check out as nautiloid right? Problem is, I don't think that there were any nautiloids in the Campanian age that were shaped like this, unless I'm mistaken. Is anyone here familiar with late cretaceous nautiloids of the Western Interior Seawway? Link to comment Share on other sites More sharing options...
Plax Posted July 7, 2020 Share Posted July 7, 2020 Hard to tell what shape it is from the pic. We have Eutrephoceras here in NC in our Campanian and Maastrichtian and believe it is also found in the western interior seaway. Not saying yours is this but better pics might help. 2 Link to comment Share on other sites More sharing options...
Norki Posted July 7, 2020 Author Share Posted July 7, 2020 2 hours ago, Plax said: Hard to tell what shape it is from the pic. We have Eutrephoceras here in NC in our Campanian and Maastrichtian and believe it is also found in the western interior seaway. Not saying yours is this but better pics might help. Yep, Eutrephoceras is also present in these deposits. This doesn't strike me as the same shape though. I didn't collect this one, so I can't get any other pics, but here's an enlarged photo. This is essentially all that was exposed, the place where the rock hammer is set didn't have anything else visible. 1 Link to comment Share on other sites More sharing options...
jpc Posted July 8, 2020 Share Posted July 8, 2020 I thought it would be a nautiloid, until you showed this last photo. Now I am confused. Link to comment Share on other sites More sharing options...
Plax Posted July 8, 2020 Share Posted July 8, 2020 me also Link to comment Share on other sites More sharing options...
Norki Posted November 9, 2020 Author Share Posted November 9, 2020 Sorry to bump this, but I'm still really puzzled by this specimen and would like to expose it to some fresh eyes and opinions. Can someone tag any users who is familiar with Bearpaw formation or similar deposits like the Pierre Shale? Link to comment Share on other sites More sharing options...
Plantguy Posted November 10, 2020 Share Posted November 10, 2020 (edited) Neat find! Here's a Pierre Shale reference that has Eutrephoceras in figure 14...unfortunately its not figured/internal structure exposed as yours appears to be....you can download as a pdf file. The molluscan and brachiopod fauna of the Late Cretaceous Pierre Shale (Baculites compressus/Baculites cuneatus biozones) near Kremmling, Colorado LA Sava - 2007 - scholarcommons.usf.edu 5. Eutrephoceras dekayi (Morton) 6. Eutrephoceras dekayi (Morton) 7. Eutrephoceras dekayi (Morton) 8. Eutrephoceras dekayi (Morton) 9. Eutrephoceras dekayi (Morton I remembered seeing an interesting article about Nautiloid predation from quite awhile ago....I'm not an cephalopod person but the figure in that article mentions an Argonautilus....Its Campanian from Calif?.... Erle G. Kauffman, Palaios Vol 19 No 1 2004 Mosasaur Predation on Upper Cretaceous Nautiloids and Ammonites from the United States Pacific Coast. I throw this out there as the image has the compression orientation like yours....I'd start with Eutrephoceras research and go from there. I even had some fun and juxtaposed the image of yours rotated next to the figure from this article cause I really dont want to do the dishes right now....... Good luck on narrowing down an ID... Regards, Chris Edited November 10, 2020 by Plantguy Added genus/species and corrected view language 3 Link to comment Share on other sites More sharing options...
Norki Posted November 10, 2020 Author Share Posted November 10, 2020 @Plantguy Thanks a lot for the resources, I'll have to spend some time diving into them. Eutrephoceras does seem to be the most likely ID at this stage, though I can't help but wonder why, for lack of a better term, it's so sausage-shaped, rather than helical. That is to say that the apparent septa don't appear to converge to a central point, and give the impression of a very loose coil, unlike the tightly-angled helical shape seen in Eutrephoceras. They also appear to be fairly straight, lacking the gentle C-shaped curve seen in the Eutrephoceras septa. I suppose these irregularities could be attributed to the preservation of this particular specimen, and Eutrephoceras is still far and away the best guess so far. Maybe next year I can go back to this site and look for more clues as to what this could be. Link to comment Share on other sites More sharing options...
Plantguy Posted November 17, 2020 Share Posted November 17, 2020 Good luck! Years ago I had contacts thru Ralph Imlay and with David Jones who were phenomenal and into ammonites and other similar aged critters....Sorry I dont have any current go to resources to narrow it down..if I run into one I'll let you know. @piranha Regards, Chris Link to comment Share on other sites More sharing options...
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