upper ordovician orthocone nautiloid?

[ottawafossil]

Hi, I found this fossil a few years ago on the shoreline of lake ontario right in the city of Kingston Ontario. I believe the exposures here are upper Ordovician age limestone (Gull River formation) however there may have been fill brought in from elsewhere to stabilize the shoreline so this fossil may not be exactly local. It looks to have a siphuncle (acentral) and sutures (relatively close together) so I thought it appeared to be some type of orthocone nautiloid of some type. Based on Bill Hessin's field guide "South Central Ontario Fossils" I thought i might be Gonioceras anceps or Actinoceras but I really don't know. The pics here are not great, but hopefully someone has some ideas. 

Thanks

[Fossildude19]

@FossilDAWG

[Kane]

Just to help out our nautiloid experts, could you post a picture of the outside of the specimen showing the annulations/striations? Those can really help in pinpointing an ID.  

[FossilDAWG]

Actinocerids have a very large siphuncle that expands within each cameral chamber so it looks like a series of fat discs.  In addition both the siphuncle and the adjacent parts of the camerae are filled with deposits, and the siphuncle lies in direct contact with the outer shell, so that part of the shell was weighted down and lay in contact with the sea floor.  Also Gonioceras was quite flattened, and the camerae were bent sharply back towards the the apex (pointy end).  These features are not evident in your specimen.  Rather, as far as I can tell from the photos, the siphuncle is linear (not expanded within the camerae) and lacks deposits so it is mostly filled with sediment.  That suggests that your specimen is more likely to be an endocerid.  Endoceras is one of the more common nautiloids in the Gull River, and is the best candidate ID in my opinion.

 

Don C

[doushantuo]

I can recommend:

edit: i just realized something:this might look like I endorse W*l*y:it's freely available,or i wouldn't post it

[doushantuo]

(Fischer & Teichert):

[doushantuo]

one of the best?

(about 9,40 Mb)

[doushantuo]

(Chen et al,1991)