Burlington limestone fossil IDs

[treebarkjerry]

Hey all, hope it's ok to do 2 for 1 here. Both of these were found in a creekbed in Pike County Illinois while hunting for chert in the Burlington limestone formation. 

The first looks like urchins I've seen from other places but with a lot less detail. Possibly a crinoid impression below it.

The second I don't even know where to start. It's a split rounded cobble with....something going on inside it.

Mostly used to finding crinoids and horn corals in the area so these really took me by surprise.

Thanks for looking.

 

[Monica]

These look odd to me, too!

 

Perhaps the first item is a cast of something, which accounts for the lack of details?  Or could it be the bottom-end-view of a rugose coral?

 

And your second item resembles (to me, at least!) the top-end view of a rugose coral showing the septa - see photo below:

(Image is from https://www.digitalatlasofancientlife.org/learn/cnidaria/anthozoa/rugosa/)

 

But I am definitely not a specialist, so let's wait for others to chime in with their thoughts, too.

 

Welcome to the forum, by the way! 

[minnbuckeye]

Burlington limestone says crinoid unless proven otherwise!!!!!!! I will go with a crinoid cup for the first specimen. It seems like I can see where the stem may have attached. 

 

 Mike

[DPS Ammonite]

16 hours ago, treebarkjerry said:

Hey all, hope it's ok to do 2 for 1 here. Both of these were found in a creekbed in Pike County Illinois while hunting for chert in the Burlington limestone formation. 

The first looks like urchins I've seen from other places but with a lot less detail. Possibly a crinoid impression below it.

The second I don't even know where to start. It's a split rounded cobble with....something going on inside it.

Mostly used to finding crinoids and horn corals in the area so these really took me by surprise.

Thanks for looking.

 

 

How thick is this rock? If it is disc like and not too thick it may not be a horn coral.

 

It may be a disc shaped sponge. See any sponge spicules especially in the bottom photo? Are you able to dissolve it out out the rock if it is silicified and the base rock is limestone? See an example of a silicified sponge from the Pennsylvanian Naco Formation in Arizona, Chaunactis olsoni: 

 

 

 

Edited June 28, 2020 by DPS Ammonite

[Jackson g]

First picture is the bottom of a crinoid cup like Mike previously suggested. Sometimes the steinkerns preserved more detail. Heres a picture of one I prepared, with the red line showing what I think is the part of your crinoid exposed.

[treebarkjerry]

On 6/28/2020 at 4:27 AM, DPS Ammonite said:

How thick is this rock? If it is disc like and not too thick it may not be a horn coral.

 

It may be a disc shaped sponge. See any sponge spicules especially in the bottom photo? Are you able to dissolve it out out the rock if it is silicified and the base rock is limestone?

 

Thanks for the replies, everyone.  Was hoping for an urchin but I accept the crinoid cup consensus.

The second item is only a few cm thick, and rounded on the back side. This is how I found it so no idea what the rest of it looked like or how big it was. The base rock is not limestone, but chert, so cannot dissolve. Don't see any sponge spicules, but had to google what that was so I could be looking for the wrong thing.

[DPS Ammonite]

1 hour ago, treebarkjerry said:

The second item is only a few cm thick, and rounded on the back side. This is how I found it so no idea what the rest of it looked like or how big it was. The base rock is not limestone, but chert, so cannot dissolve. Don't see any sponge spicules, but had to google what that was so I could be looking for the wrong thing.

 

The close up looks even more like a sponge. If it is not a sponge, I don’t  what to guess what it is. I’d give you the name of a sponge expert but I can find any myself. You might send a photo to the paleontology department of your local university. Let us know what you find out.

 

Everyone, know any local professionals that would like to see this?

[Jackson g]

On 7/1/2020 at 6:02 PM, treebarkjerry said:

 

Thanks for the replies, everyone.  Was hoping for an urchin but I accept the crinoid cup consensus.

The second item is only a few cm thick, and rounded on the back side. This is how I found it so no idea what the rest of it looked like or how big it was. The base rock is not limestone, but chert, so cannot dissolve. Don't see any sponge spicules, but had to google what that was so I could be looking for the wrong thing.

Looks like half of a split chert concretion. I split a chert concretion perfectly in half about half a year ago and found something identical to what you have pictured here. Had the same pattern/ features shown. It was probably about 4.5 inches in length. Back then I used to split these concretions only for their crinoids, so greedily I thought nothing of it and just hocked it back into the creek. I regret it now, but I did save one other small crystalline chunk i found the same day that I'll post later when I'm off of work for comparison. I think it's probably a sort of sponge fossil too. I can provide you Dr. Thomas W. Kammers contact info if youd like through pm, he knows a lot about Mississippian fauna in the area and surrounding states.

[Shellseeker]

Another opportunity to learn...   Thanks !!!

An Oregon hunter searching a creek in Illinois.

[Jackson g]

Heres that piece I kept from a 2nd split concretion I was speaking of earlier. Really wish I had kept the first split half instead of throwing it back to nature, was identical to what you have pictured.

 

[DPS Ammonite]

1 hour ago, Jackson g said:

Heres that piece I kept from a 2nd split concretion I was speaking of earlier. Really wish I had kept the first split half instead of throwing it back to nature, was identical to what you have pictured.

 

Give us a clear photo from the side.

 

It looks most like a sponge to me.

[Jackson g]

Forgot to upload, it's about 3-4mm thick.

[treebarkjerry]

On 7/9/2020 at 8:07 AM, Shellseeker said:

Another opportunity to learn...   Thanks !!!

An Oregon hunter searching a creek in Illinois.

 

Originally from Illinois. I travel a lot and rockhound everywhere I go.

 

On 7/9/2020 at 12:43 AM, Jackson g said:

I can provide you Dr. Thomas W. Kammers contact info if youd like through pm, he knows a lot about Mississippian fauna in the area and surrounding states.

 

Jackson g, I sure would appreciate his contact info. would like to try and settle this once and for all