Reklaw 2 Posted June 24, 2019 So this is a fossil from Beloit Wisconsin found in the Platteville formation. I am pretty sure it is a cephalopod but I have no idea what genus or species. The siphuncle is hollow except for two septa that run right through it. 3" post-it note for scale. Share this post Link to post Share on other sites
FossilNerd 2,209 Posted June 25, 2019 I agree that it is a cephalopod, but I think it will be hard to say what genus or species this is. There are a few different straight cephalopods found in the Platteville Formation (Ordovician). It might be a section of Actinoceras, as I believe it is fairly common in that formation, but not sure. Share this post Link to post Share on other sites
Manticocerasman 2,431 Posted June 25, 2019 I would keep it at "Cephalopod orthocone" It will be hard to make out more of it. Share this post Link to post Share on other sites
FossilDAWG 5,840 Posted June 25, 2019 The straight siphuncle without deposits,and the lack of deposits in the camerae, is suggestive of a michelinocerid. Actinocerids have large siphucles, which expand into the camerae (so they look like a string of flattened disks strung together), filled with deposits. In addition the camerae are filled with deposits on the ventral side. Basically, michelinocerids were active swimmers with lightly built shells and actinocerids lived on the sea floor and had heavy deposits in their shell to weight them down. Don Share this post Link to post Share on other sites
Reklaw 2 Posted July 1, 2019 Thank you! Looks about right to me! Share this post Link to post Share on other sites
Reklaw 2 Posted July 12, 2019 An update to this post, I found a very similar looking fossil in "The Geology of Minnesota" (1872) and it is labeled as a Tripteroceras planodorsatum. And I found another one that was out of the matrix with the characteristic flattened triangle shape of the Tripterocerids, so I am pretty sure it is in fact a T. planodorsatum not a michelinocerid. Share this post Link to post Share on other sites
