Bone, branch or other

[Riverrun]

Supposedly these came from the Missouri River valley in central South Dakota.  One old timer says he was told they are petrified bones.    They are very solid and high strength.   Somewhat symmetrical on the longitudinal axis. Sandstone appearance on surface.  What are these, any ideas?

[caldigger]

These looks very geologic.  Perhaps unfilled cracks of a higher resistant rock and have weathered out of the softer country rock.

Definately not bone of any kind.

 

From the looks of their surroundings, I think they were brought in.

[Mark Kmiecik]

They are not bones. I don't see any features that are normally present in preserved bones and they're the wrong shape. They are interestingly weathered rocks and their origin is worth investigating. The one with the 'ridge' is intriguing. 

[Auspex]

Akin, i think, to Loess Kinchen, geologic features found in loess soils. Usually smaller, they can take fantastical shapes (hence the name, which means "Little Loess Children").

[Rayminazzi]

I could be way off base with this one but does anyone think that looks like an ammonite keel sticking out in the second and third pictures?

[Ludwigia]

5 hours ago, Rayminazzi said:

I could be way off base with this one but does anyone think that looks like an ammonite keel sticking out in the second and third pictures?

By George! You've got a point there.

[Mark Kmiecik]

19 hours ago, Rayminazzi said:

I could be way off base with this one but does anyone think that looks like an ammonite keel sticking out in the second and third pictures?

That part caught my attention also -- ammonite keel is a good suspect. If these are large concretions, I wonder what else may lurk inside.

[Riverrun]

Thanks for the feedback.  These are very interesting specimens.   I agree that the two pieces do appear geological, but the ridges, symmetry and strength are very intriguing.  Here are a few more pictures of the shorter specimen, it also has ridges.  Any other thoughts are welcome...