Marine Flora? Thanks for any help!

[Jenks Teacher]

These were found near Lake Texoma in the same layer as ammonites and echinoids. However, like my post yesterday, I haven't been able to find pictures of anything similar to these. The white ruler in the pictures is 15 millimeters long. Both cylindrical shaped fossils are approximately 6 inches in length, roughly 11 inches circumference, and 3 inches in diameter. Thanks in advance for looking and any help you might give. General comments and questions are obviously welcome!

[Rockwood]

I don't think the larger cylinder shapes are fossils. The smaller cylinders in them are burrow traces. 

[Jenks Teacher]

17 minutes ago, Rockwood said:

I don't think the larger cylinder shapes are fossils. The smaller cylinders in them are burrow traces. 

Interesting. Burrow traces from under the seafloor? I wonder if the cylinders themselves are the result of burrows being filled by deposits? 

[Rockwood]

27 minutes ago, Jenks Teacher said:

Interesting. Burrow traces from under the seafloor? I wonder if the cylinders themselves are the result of burrows being filled by deposits? 

Many things burrow in the sea floor and many things live in burrows in the seafloor. The burrows are preserved as natural casts. Smaller burrows are seen inside larger ones. The top photo could be an example, but the size and shape make me doubt it.