Looking for Cephalopod ID

[I_gotta_rock]

I could really, really use some help on this one! I found this 1.5" cephalopod in the Cretaceous MT Laurel sand at the C&D Canal, Delaware City, DE (north side). There are only four cephalopods listed for this site in the Delaware guide, the straight-shelled Bacculites ovatus, Oxybelaoceras (which is heavily ribbed and doubles over on itself tightly in a U shape) and the golden bullets of Belemnitella americana. There are two other cephalopods listed for the canal zone - at different sites- in the Delaware guide, but they are both tightly-coiled.This one was loosely-coiled, probably in a spiral, and lightly ribbed all the way around. Most of the ribbing has broken off of this specimen, but you can just make out how they go all the way around at the upper left edge of the first photo. The closest thing I can find to this is a lightly-ribbed, loosely-coiled Cirroceras conradi. It is listed in the Cretaceous Fossils of New Jersey, through which all the canal formations run, but the only specimens found in NJ were in the Navesink formation. C. conradi also gets smoother on the inside of the coil, at least in the image in the book. I'm not very good at figuring out the text descriptions. The C&D Canal isn't supposed to cut through the Navesink formation, either, but it is as close as I can find. I'm thinking this might be one specimen I should not lose in a drawer, but I have no idea what it is or where to turn once I figure it out. It just isn't supposed to be there!

[piranha]

These papers have many more species to consider.  Didymoceras platycostatum looks like a good possibility.

 

Kennedy, W.J., & Cobban, W.A. (1994)

Upper Campanian ammonites from the Mount Laurel Sand at Biggs Farm, Delaware.

Journal of Paleontology, 68(6):1285-1305

 

Kennedy, W. J., & Cobban, W.A. (1997)

Upper Campanian (Upper Cretaceous) ammonites from the Marshalltown Formation-Mount Laurel boundary beds in Delaware.

Journal of Paleontology, 71(1):62-73

 

 

 

[I_gotta_rock]

That's awesome, but I can't open the links. I found a link on ResearchGate to one of them, but as I am not a paleontologist or published in any field other than Communication Theory,  I have to wait and see if they'll grant my request.

[abyssunder]

Don't worry, be happy!

 

Here it is :  W. J. KENNEDY AND W. A. COBBAN. UPPER CAMPANIAN (UPPER CRETACEOUS) AMMONITES FROM THE MARSHALLTOWN FORMATION-MOUNT LAUREL BOUNDARY BEDS IN DELAWARE. J. Paleont., 71(1), 1997, pp. 62-73

 

[I_gotta_rock]

Wow! That's it!  Thank you so much! Rare find indeed if it takes this much to identify the thing!

[piranha]

Always happy to help.

I posted both papers last night, but somehow the links malfunctioned.

Here's the other Kennedy/Cobban paper on the Mt. Laurel ammonites.

 

Kennedy, W.J., & Cobban, W.A. (1994)
Upper Campanian ammonites from the Mount Laurel Sand at Biggs Farm, Delaware.

Journal of Paleontology, 68(6):1285-1305

 

 

 

[I_gotta_rock]

I have them both on my had drive for future reference now. Thanks!  Don't know why I couldn't get the link to work this morning. I am calling it D. platycostatum. Both species of Didymoceras, but this one has shallower grooves than D. cheyennense. Or should I just call it Didymoceras sp.  since the groove depth could be a trick of the lighting?  As much trouble as it was to identify, I thought this might be a good one for the FF database.

 

While we're at it, anyone have any good ostrea identification papers? I have at least 5 different species I pulled out of the same honey hole as this ammonite. I can identify three of them so far. 

 

[Plax]

make sure you look at the suture pattern closely for your ammonite ID.