Ordovician Unknown

[minnbuckeye]

Found this at a site that had a rock slide. The cliff is Decorah shale and Platteville limestone. Thought this was a Rugosa Coral on site. When I returned home and cleaned it up a bit, it appeared like something I had yet to find. It is very thin/delicate and hollow.

 

 

 

The other Platteville unknown that I found was this: 

 

 

 

 Will be patiently waiting!!!!

 

Mike

 

 

[FossilDAWG]

Won't have to wait long.  These are Zitteloceras, a type of nautiloid cephalopod.  The curve and the frilly ornamentation are characteristic.  Below is figure showing a typical specimen (source: V. E. McKELVEY  (1939). AN ORDOVICIAN ZITTELOCERAS FROM WISCONSIN. JOURNAL OF PALEONTOLOGY, VOL. 13, No. 1, PP. 74-76.).  Your specimen may belong to a different species.

 

Don

[minnbuckeye]

Don,

Thanks for the great (and quick) response! Are you saying both specimens posted are Zitteloceras? Picture 1 is so different from picture 2. Also, can I continue to prep underneath of this cephalopod or like the clay molds pictured, the bottom is not worth exposing?

[FossilDAWG]

They may be different species, but I think it more likely that the ornament was just somewhat variable, and also because it is so fragile erosion can create a substantially different appearance.  I would not try to remove them from the matrix, and I'd be very delicate about prepping them much further because of the delicacy of the frills.  I have a few specimens from the Ottawa ON area where the frills are preserved on one side (where they were naturally exposed) and the shell is missing entirely, exposing the internal mould on the side that was facing the matrix, as the shell tends to stay with the matrix.  Not too bad, but the shell without the frills looks just like other unornamented curved nautilods such as Richardsonoceras.  I think Zitteloceras with good ornament are not all that common, so you don't want to risk damaging them when you do find them, IMO.

 

Don