Possible tetrapod fossil found - Illinois

[georgiad2234]

Hi all,

 

I recently found this fossil, and I was hoping I could find some help here identifying it. I found it at Fort Sheridan in Illinois, and wasn’t expecting something that looked like it could be vertebrate. I’m familiar with the fossils with the area, and was surprised to find something like this. Any ID suggestions or suggestions for where to get it ID’d would be appreciated. Someone I talked to said it may be an amphibian/tetrapod fossil (potentially an egg)

 

Description of fossil: small potato shaped rock with skull and thorax of specimen showing. “Feet” protruding from the bottom, and there appears to be a little hand covering the skull on one side.

 

Little hand over face

Top view showing little hand over right side of skull

Right side view

Left side view

Edited April 2, 2022 by georgiad2234

[Lone Hunter]

Pretty sure it isn't a tetrapod, or egg,  but a suggestively shaped rock.

[Fossildude19]

Welcome to the Forum.

 

I think we are looking at cross sections through a brachiopod in dolostone.

Not seeing any bone texture, or skull morphology.

 

Fort Sheridan is in Lake County, Illinois.                                                      Which is where Silurian Dolostone is the exposed bedrock:

 

 

 

 

 

The Silurian is way before amphibians were around.  

 

[georgiad2234]

1 minute ago, Fossildude19 said:

Welcome to the Forum.

 

I think we are looking at cross sections through a brachiopod in dolostone.

Not seeing any bone texture, or skull morphology.

 

Fort Sheridan is in Lake County, Illinois.                                                      Which is where Silurian Dolostone is the exposed bedrock:

 

 

 

 

 

The Silurian is way before amphibians were around.  

 

Thank you for the response. It’s a weird cross section if it is then! 
 

Just to clarify, the matrix is dolostone? Do you know what mineral the fossil portion is made of? Is that any help in narrowing down the time period this is from?

[Fossildude19]

I think it is dolostone, but impossible to tell from just a photograph.

The shell material may be calcite.

[Mark Kmiecik]

Mason Creek, Illinois is about halfway between Davenport and Peoria -- which is not even remotely close to Fort Sheridan. If you meant Mazon Creek, it is more than 60 miles SSW as the crow flies, 80 to 90 by road. The dolomite in which the mollusc is preserved is nothing like the ironstone concretions of Mazon Creek found in the Francis Creek Shale member found directly above the Colchester #2 Coal stratum, neither of which is present in the strata found in the Fort Sheridan area which is composed of hundreds of feet of limestone.

[georgiad2234]

4 hours ago, Mark Kmiecik said:

Mason Creek, Illinois is about halfway between Davenport and Peoria -- which is not even remotely close to Fort Sheridan. If you meant Mazon Creek, it is more than 60 miles SSW as the crow flies, 80 to 90 by road. The dolomite in which the mollusc is preserved is nothing like the ironstone concretions of Mazon Creek found in the Francis Creek Shale member found directly above the Colchester #2 Coal stratum, neither of which is present in the strata found in the Fort Sheridan area which is composed of hundreds of feet of limestone.

I’m fully aware it would be very out of place, when suggesting what it could be I was under the impression it could have been moved to this a location nearby for landscaping. Sorry I didn’t put that in the post. This entire area has had a lot of erosion prevention put in. To me, it wasn’t outside the realm of possibility it was moved from its original location and then washed onto shore after the weather we’ve had recently. 
 

i appreciate your response as to why it doesn’t fit with the fossils found at mason creek.

 

[Mark Kmiecik]

3 hours ago, georgiad2234 said:

I’m fully aware it would be very out of place, when suggesting what it could be I was under the impression it could have been moved to this a location nearby for landscaping. Sorry I didn’t put that in the post. This entire area has had a lot of erosion prevention put in. To me, it wasn’t outside the realm of possibility it was moved from its original location and then washed onto shore after the weather we’ve had recently. 
 

i appreciate your response as to why it doesn’t fit with the fossils found at mason creek.

 

 

Possible, but not probable. There's lots of quarries much closer from which to haul fill. They wouldn't spend the extra money needed to haul tons of rock from 80 miles away when they can get it from 20 miles away. I've often imagined that possibility and would have welcomed it, but unfortunately the slippery, slimy Francis Creek shale is not something you would want to use as fill. It's as slippery as slush is in the winter, and would never be used for landscping. I have found a few things in the Chicago area which were brought in from somewhere else, so it is a possibility. However, the dolomite that composes your find is nothing like the iron siderite of the Mazon Creek concretions, which, by the way, are found only 1-1/2 hours south of you. If you ever get a chance, you should check it out. If you're into fossils or thinking you might like to be, search "mazon creek" in the search bar on this forum to get an idea of the king of things you might find there.

 

Good Luck and the best of wishes,