Austin Chalk formation fossil?

[Creek - Don]

I found this piece of rock with strange shape in the rock quarry nearby Interstate 35 between Temple and Waco, Texas.    I did't see much other fossils other than this piece.  Wonder what this is?  

Formation is on Austin Chalk. 

[Scylla]

Is the "fossil" made of flint or chert?

[Creek - Don]

Just now, Scylla said:

Is the "fossil" made of flint or chert?

No, these rocks are limestone rocks.  Very chalky material.  Late Cretaceous ocean sediments. 

[Scylla]

@Uncle Siphuncle might know then

[DPS Ammonite]

The outward shape does not look like any creatures. This might be a burrow or concrete on with parallel bedding planes.

[Creek - Don]

25 minutes ago, DPS Ammonite said:

The outward shape does not look like any creatures. This might be a burrow or concrete on with parallel bedding planes.

 

Thanks DPS. I knew I hesitate to call this a fossil.   Had to give a shot!  

[Heteromorph]

A heavily weathered Magadiceramus inconstans, an odd inoceramid in that it suddenly decides to start growing more down than out at some point during its ontogeny. I have found many of these in the Upper Coniacian horizon of the Atco formation of North Texas, and have seen some that Keith Minor has found from the same exposure that your's comes from.

 

If you visit again, keep an eye out for ammonites like Prionocycloceras gabrielense and Forresteria sp., as he reported finding them at the same exposure along Interstate 35. 

 

Here is one that Keith found at the same site:

 

 

Here is a rather extreme example of mine from North Texas:

 

 

[Creek - Don]

17 minutes ago, Heteromorph said:

A heavily weathered Magadiceramus inconstans, an odd inoceramid in that it suddenly decides to start growing more down than out at some point during its ontogeny. I have found many of these in the Upper Coniacian horizon of the Atco formation of North Texas, and have seen some that Keith Minor has found from the same exposure that your's came from.

 

Thanks Heteromorph.  That is an oddity. Never seen an Inoceramid growing down like that before .   I also have some of Prionocycloceras gabrielense  in my collection, but they were poorly fossilized.  For some reason, when city of Dallas needs erosion control rocks, it comes from central or west Texas.  They dump those rocks under the bridges and I get to fossil hunt them under the Dallas bridges.