Pennsylvanian Aged Mystery Fossil

[RCFossils]

This is a very odd fossil that I collected from a Pennsylvanian aged black shale site in North Central Illinois.

i have been collecting this site for many years and have never found anything like it.

The specimen measures approximately 3”.

The site primarily consists of a Thylacocephalan type arthropod along with  a variety of fish and a few nautiloids.

it is very similar to the Mecca Quarry Shale of Indiana.

My best guess is that it is some type of nautiloid or possibly a spiral coprolite.

Any suggestions would be appreciated.

[Rockwood]

Maybe the list should include large bivalve ?

[TqB]

Interesting - what's the preservation like with the definite nautiloids?

[connorp]

Maybe a strangely compressed Orbiculoidea? In the Pennsylvanian limestone I hunt, I find them in a lot of weird noncircular shapes.

[westcoast]

42 minutes ago, connorp said:

Maybe a strangely compressed Orbiculoidea? In the Pennsylvanian limestone I hunt, I find them in a lot of weird noncircular shapes.

That's what I was initially thinking but the growth lines just don't quite look right for Orbiculoidea.

[piranha]

A colleague replied:

 

"Interesting. It looks like a straight nautiloid to me but not the common Pseudorthoceras knoxense of the Pennsylvanian. Probably a new species and a holdover of Silurian-Devonian oncocerids, such as Hexameroceras. The aperture looks like it has at least one keyhole segment."

[RCFossils]

9 hours ago, TqB said:

Interesting - what's the preservation like with the definite nautiloids?

Here are a few images of the other nautiloid that I have found at the site.

The first I believe is a type of Metacoceras. It is the only one that I have found at this site.

The second is a Pseudorthoceras. I have found a few over the years.

[RCFossils]

9 hours ago, TqB said:

Interesting - what's the preservation like with the definite nautiloids?

Here are a few images of the other nautiloids.

The first I believe is a type of Metacoceras. It is the only one that I have found at this site.

The second is a Pseudorthoceras. I have found a few over the years.

[RCFossils]

1 hour ago, piranha said:

A colleague replied:

 

"Interesting. It looks like a straight nautiloid to me but not the common Pseudorthoceras knoxense of the Pennsylvanian. Probably a new species and a holdover of Silurian-Devonian oncocerids, such as Hexameroceras. The aperture looks like it has at least one keyhole segment."

Thanks Scott!

This would be quite exciting.

please let me know if your colleague knows of anyone who might want to work on it.

I would be happy to donate it if it turns out to be something important.

[TqB]

44 minutes ago, RCFossils said:

Here are a few images of the other nautiloids.

The first I believe is a type of Metacoceras. It is the only one that I have found at this site.

The second is a Pseudorthoceras. I have found a few over the years.

Thanks, that seems to support this one being an unusual nautiloid too, as Scott's colleague suggests, let's hope so! (The Metacoceras is a handsome thing.  )

[GeschWhat]

Interesting! Not a spiral coprolite. They would not have an outer shell like that. I have a squid from the Solnhofen. The soft body tissue of the squid looks very much like calcium phosphate seen in carnivore coprolites. That said, the underlying material on your specimen does look phosphatic. Does soft body tissue fossilize in that area? 

[piranha]

3 hours ago, RCFossils said:

Thanks Scott!

This would be quite exciting.

please let me know if your colleague knows of anyone who might want to work on it.

I would be happy to donate it if it turns out to be something important.

 

 

For expert evaluation I would recommend: Christian Klug, Dieter Korn, Neil Landman, Royal Mapes ... just to name a few.