Michigan Fossil ID

[townsera]

This was found at Millennium Park near Grand Rapids, MI. I'm thinking Bryozoan?...but does anyone have an idea of species?

[Kane]

I’m thinking coral as I can make out the septal striations. As to species, I’m not much help.  

[Fossildude19]

@TqB

[Rockwood]

There may be a rugose coral involved, but I sort of doubt it. I think there is a bryozoan encrusting something else there.

[FossilNerd]

16 hours ago, Kane said:

I’m thinking coral as I can make out the septal striations. As to species, I’m not much help.  

I think it is coral as well. I see the septal striations in a couple of areas. Such as those circle here. I don’t think there is enough to go on to identify the species, but others may disagree. 

 

[Rockwood]

17 hours ago, Kane said:

septal striations

Is there a distinction between striations and actual septa ? If so where are the septa, and why aren't they oriented radially to a point ?

[FossilNerd]

I took @Kane as meaning very faint evidence of septa when saying striations. So you can see faint lines of what is left of the septa.

 

Seems like a vertical cross section to me that has been worn down (I’m guessing by water since it is smooth) and we are seeing the faintest hint of a coral.

 

Like this one from my collection, but worn down/weathered away more.

 

[Kane]

1 hour ago, Rockwood said:

There may be a rugose coral involved, but I sort of doubt it. I think there is a bryozoan encrusting something else there.

Bryozoan pores would be much smaller than this.  The coral structure is even more apparent in Wayne's close-up / red outline of the OP's piece, and looks quite similar to the kinds of Devonian coral that weathers and washes up across Michigan and southwestern Ontario. But, as Wayne suggested, it may be a bit too much on the weathered side to really pinpoint an ID.

[Rockwood]

Could it be the chalice of a young or naturally sectioned specimen ? The configuration to the left representing septal insertions.

The mix of radial and linear structure is confusing. I do agree that the elements look like rugose coral. 

[Kane]

Could be! I've seen them in so many configurations (twisted, doubled over, wending) that a cross section can reveal more than one orientation. For instance, imagine a horizontal slice of a cup that looks like an upside down 'L', which might show both radial and linear structure.