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A Fun Illinois Pennsylvanian Trip


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connorp

This weekend I was able to spend a couple hours breaking rock at one of my favorite Pennsylvanian sites. This site exposes the lowest units of the Carbondale Formation, from the top down: Mecca Quarry Shale (MQS), Francis Creek Shale, Colchester No. 2 Coal, paleosol. At various times both the St. Peter Sandstone and Platteville Group (both Ordovician) have been exposed at the bottom of the pits (they were not visible this trip), representing a major unconformity in the area. The concretions from the Francis Creek Shale (i.e. Mazon Creek fossils) are not productive here - my area of focus was instead the MQS.

 

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As far as I can tell, the MQS is no longer exposed here. But at the base of the MQS in some locations are large limestone concretions which is what we find here. The limestone is very hard and when freshly exposed does not split easily, so collecting is best limited to limestone which has been weathering for some time.

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The most abundant fossils in the MQS here are bivalves, but occasionally brachiopods, cephalopods, gastropods, plant material, and fish bits show up. Here are some of my favorite finds.

 

A partial Listracanthus hystrix shark denticle

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Dunbarella sp.

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Fish regurgitant (mainly palaeoniscoid bits)

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Desmoinesia muricatina with an attached spine

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Pyritized Dunbarella sp.

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Pseudorthoceras knoxense with several encrusting serpulid worm tubes

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Just one of many tiny isolated fish bones found

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Palaeoniscoid scale

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The base of a Petrodus shark denticle

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Possibly a bit of cartilage?

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This is perhaps my most interesting find, although I am not positive on the ID. I believe the spine is a fin spine from an acanthodian, and thus would assume the scales are acanthodian scales? Any thoughts are appreciated. @jdp

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Edited by connorp
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Interesting finds. The quarry looks much different from the last time I was there a couple years ago. Still you made out with intriguing material. Unfortunately I can't help with ID's.

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Praefectus

Great finds! :thumbsu:

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historianmichael

Really cool! I love Pennsylvanian fish material. The Pseudorthoceras knoxense with worm tubes is awesome.

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Nice fish. That last one is definitely Acanthodes or the equivalent (the taxonomy on that group of animals is incomplete)

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Awesome finds!

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deutscheben

Nice finds, I was disappointed I couldn't make it to the trip this year. The acanthodian spine is very cool!

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connorp

I was splitting some rocks I brought back and came across this nice scale today. It's decently large, around 5mm in length. Maybe palaeoniscoid? I am not sure, any thoughts?

scale.thumb.jpg.aab9d6b927562bbaa4c3e556a65864bd.jpg

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Tidgy's Dad

Some excellent finds. I love the Dunbarella and Desmoinesia in particular.:)

The 'worm' covered Pseodorthoceras is magnificent, but those can't be serpulids as they didn't evolve until the Permian. Pre-Jurassic ' serpulids' are nearly always actually microconchids, if spirally coiled, or in the case of your specimens, probably some sort of cornulitiid.  

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20 hours ago, connorp said:

I was splitting some rocks I brought back and came across this nice scale today. It's decently large, around 5mm in length. Maybe palaeoniscoid? I am not sure, any thoughts?

scale.thumb.jpg.aab9d6b927562bbaa4c3e556a65864bd.jpg

 

Coelacanth scale. Definitely not 'paleoniscoid'

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