Limestone (Silurian?) Fossil. ID Help Please

[KankRat]

I found this fossil along the banks of Lake Michigan in NW Indiana. it is limestone chunk rock that was put there. 

The creature is a little over 4.5 inches long and about and 2 inches wide at it's widest point. The left side appears to be very round, like a scoop of ice cream sitting in a cone..  The zig-zag pattern is very pronounced. That's what caught my eye. 

 

Fossil NW Indiana by Mark Kasick, on Flickr

[KankRat]

There is only one shot here.  Last time I posted none could see the one I uploaded so I liked this one to my flickr account.

[tmaier]

Looks like an internal cast of the cephalopod called Phragmoceras.

[Kane]

I agree with @tmaier but I also agree the jagged tooth-like pattern is quite intriguing.

[tmaier]

I see that wiggly pattern in an illustration of Phragmoceras carmani in the book "Fossils of Ohio", and is it the margin at the opening of the shell. I wish I could post that image from this book, because it is almost an exact match. Right down to the blobular icecream on the end. =-)

[KankRat]

Wow thanks folks. Phragmoceras carmani is not showing up on any Google searches.  I guess I will have to hit ...."gasp" the Library.  Dying to see what this thing looked like.  t

[tmaier]

Searching specifically for a species often makes google lock up with "no sites found". So then back up and just look for the genus (Phragmoceras). If that doesn't work, you keep backing up the taxonomical tree until google finds something.

https://www.google.com/search?q=Phragmoceras&btnG=Search&hl=en&gbv=1&nfpr=1&tbm=isch

The reason I didn't mention the species "carmani" in my first post was because I strongly hesitate to identify or even mention species names to people unless I'm very sure that is what it is. Often a genus or familiy will contain many similar species, and the speciment shown does not contain all the difinitive features to be classified as that species. But... people often grab that species name and run with it, and you end up with a lot of confusion on the internets when people post the very specific species, and when you look at them, it's kind of obvious that they are not all of the same species.

Short story, I mention the species name here only to refer to what I'm looking at, and not in the attempt to classify your specimen to be that exact species.

[tmaier]

This specimen might be a good candidate for "prepping out", to expose more of the anatomy of it. Sometimes an internal cast like this is kind of welded into one piece with the matrix, and can't be exposed easily, but this one looks like it has a boudary region between the matrix and the fossil that would allow at least some easy exposure.

[KankRat]

8 hours ago, tmaier said:

This specimen might be a good candidate for "prepping out", to expose more of the anatomy of it. Sometimes an internal cast like this is kind of welded into one piece with the matrix, and can't be exposed easily, but this one looks like it has a boudary region between the matrix and the fossil that would allow at least some easy exposure.


 

Yeah, I was going to take a crack at it, figuratively.  

[ynot]

45 minutes ago, KankRat said:

Yeah, I was going to take a crack at it, figuratively.  

Use care and a soft touch, or You may end up with rubble.

Tony