Mystery Star

[rocksnstars]

I am a mineral and fossil collector and an amateur astronomer and my email is rocksnstars, so rocks collected that include a star shape are special.  Most of the ones I have are the crinoid stems with star-shaped centers.  This is the first time I've seen anything like this.  I believe I have met the requirements of providing a good photo with a scale, and I know the period is Late Ordivician.  I tagged Ohio because I think that is where it is from, but it is possibly Indiana, however BOTH sites are the SAME period and well known.  I collected the two places the same day, and unfortunately during the drive home to Maine and the unloading, some of the specimens got mixed up and this was one of them.  The Ohio location is the spillway at Caesar Creek State Park, Waynesville, Ohio, US.  The Indiana one is Whitewater River Gorge, Richmond, Indiana, US.  (Each mark is 1 mm, so the "1" on the scale is 10 mm, perhaps standard.)

Edited October 15, 2018 by rocksnstars
Clarifying scale measurement.

[ynot]

Looks like a crinoid columnal. There were some that had a star shaped exterior.

[Herb]

looks like a section of crinoid  stem

[rocksnstars]

Thank you both.  I have many crinoid stems from all across the country and everyone of them is circular.  Now I know!

[Herb]

they can be stars, circles,squares, ovals and pentagrams

[abyssunder]

22 hours ago, rocksnstars said:

Most of the ones I have are the crinoid stems with star-shaped centers.

No doubt, the "lumen" infill is identical to the surrounding matrix material.
There might be exceptions of the five-folded symmetry characteristic to echinoids such as crinoids or others, as Tony and Herb said it already. The shape of the lumen might be different, no matter how the external shape of a columnal is.
I think, your specimen  has an intermediate growth, making it six- folded.

It's clear, that the sixth growth is weaker than the other five. Could it be regeneration of on injury?

[ynot]

28 minutes ago, abyssunder said:

Could it be regeneration of on injury?

Or possibly post burial deformation or post exposure damage

[abyssunder]

If it might be post burial, it might be too perfect closing the lines. I think, it was the reaction of a living echinoderm to a possible attack regenerating its structure, and I think those might be epibionts rather than endobionts.

[rocksnstars]

You've lost me!  Some crinoid columns have star cross sections was understandable.  The more recent comments are beyond my level of fossil collecting/understanding.  All I can say is that I have hundreds of crinoid stem sections and segments, and I've seen many more, and they are all circular, so the other shapes must be relatively rare.  Regardless of what it is, it is one of my very few (~10 out of 2500) specimens of a rocksnstars shape in a fossil, mineral or rock in our collection.

[ynot]

2 hours ago, rocksnstars said:

You've lost me!  Some crinoid columns have star cross sections was understandable.  The more recent comments are beyond my level of fossil collecting/understanding.  All I can say is that I have hundreds of crinoid stem sections and segments, and I've seen many more, and they are all circular, so the other shapes must be relatively rare.  Regardless of what it is, it is one of my very few (~10 out of 2500) specimens of a rocksnstars shape in a fossil, mineral or rock in our collection.

It is a nice piece, but not rare (site dependent). IE in some sites star shaped columnals can be quite rare and in other sites be plentiful.

Abbysunder  and  I were discussing possible causes of a slight deformation in the shape evident in the lower right side.

[Rockwood]

On 10/15/2018 at 9:24 PM, ynot said:

Or possibly post burial deformation or post exposure damage

The bottom left is the only area still looking good.