Student found this fossil....can you help us identify it?

[jr.nation88]

One of my students brought this in to try and ID and after much work I have not got very far. A friend pointed me to your sight because of the vast knowledge here. It was found in southeast Missouri, partially buried in a creek bed.

[Tigger]

Wow! If someone doesn't ID it here, email pictures to your closest university and have them look at it. Very interesting!

[naturegirl]

It is interesting! Will be curious to see what it is.....

[Harry Pristis]

That last image, if that is the original orientation in the earth, certainly appears to be some sort of burrows. In other words, this reminds me of an ichnofossil. Perhaps it is a highly-eroded example of something like Diplocraterion with the spreiten reduced to tooth-like nubs.

[kkglawson]

it looks like george washingtons dentures

[jr.nation88]

Not insisting on it but still trying to get a clear answer. With my major I have studied alot of rocks and yet to have come across a sedimentary rock that has spilt with such perferct/proportionate shapes. I've concluded it is chert not limestone which hurts the fossil idea but my brain is not letting me believe it is just an 'accident'. I submitted the pictures to the Eastern Missouri Palentological Society who was intrigued but also had issues so they asked me to mail it to them and they would study it. It is in route now, so we wait.................

[Harry Pristis]

That's excellent, 'Jr.' Please be certain to let us know what you find out.

It is common for chert to preserve fossils. Moreover, it is common for cryptocrystaline quartz (SiO2 - "chert") to be differentially deposited around irregularities in sediment which eventually becomes limestone. The best examples of this phenomenon are the silicified remains of marine animals in the Mississippian Harrodsburg Limestone.