Fossil ID…found in Northern Missouri. Lincoln County to be exact.

[laurachristine1970]

First and foremost, I’m new to fossil collecting and what an amazing journey it’s been.  I live in Lincoln County Missouri near the Cuivre River and have found some amazing fossils. It seems the creek that flows into the Cuivre is CHOCK FULL of “death plate fossils” (sorry if I used the wrong terminology). Being a “newbie” I have many ID’s to request. I will start today with my newest find.  

[Al Dente]

It is a steinkern of a horn coral. This is the sediment that surrounded and filled the coral, the actual coral has dissolved away.

[Fossildude19]

I agree with Rugose coral steinkern.

[DPS Ammonite]

This is an external mold (probably now silica) composed of sediments that filled the top of a horn coral also known as the calyx of a coral. The “fins” are exterior molds of the septa.
 

Steinkerns are internal molds such as the hardened sediment inside a closed bivalve.

 

https://fossillady.com/tag/helliophyllum-facts/

 

 

Edited December 23, 2023 by DPS Ammonite

[Al Dente]

27 minutes ago, DPS Ammonite said:

This is an external mold (probably now silica) composed of sediments that filled the top of a horn coral also known as the calyx of a coral. The “fins” are exterior molds of the septa.
 

Steinkerns are internal molds such as the hardened sediment inside a closed bivalve.

From here-https://www.researchgate.net/publication/237837061_Notes_on_taxonomy_and_taphonomy_of_two_Upper_Maastrichtian_Upper_Cretaceous_scleractinian_corals_from_Limburg_The_Netherlands

[DPS Ammonite]

11 minutes ago, Al Dente said:

From here-https://www.researchgate.net/publication/237837061_Notes_on_taxonomy_and_taphonomy_of_two_Upper_Maastrichtian_Upper_Cretaceous_scleractinian_corals_from_Limburg_The_Netherlands

If you take a horn coral (like the one pictured) and impress it into clay you get an external mold. A steinkern is formed in cavities that have no or minimal connection to the exterior. A calyx of a coral has a large connection to the exterior.
 

 

[DPS Ammonite]

Here are pictures of two of my Mississippian horn corals (same genus?) that are part/counterpart or positive/negative. 
 

Photo 1 is looking down into the calyx of a silicified horn coral. Note slit cavity known as a fossula marked as F and septa marked S.
 

Photo 2 shows the silicified infilling, exterior mold, of a similar horn coral with prominent septa, (marked Sm), and a fossula, (marked with Fm). OP’s fossil is similar to this form of preservation of a horn coral. Note arrow points to gap where the calcitic coral dissolved away.

[Al Dente]

1 hour ago, DPS Ammonite said:

A steinkern is formed in cavities that have no or minimal connection to the exterior.

we’ll have to agree to disagree on this one.