Sponge ID

[DPS Ammonite]

What type is this sponge from the Pennsylvanian Naco Fm. from near Payson, Arizona? The silicified sponge is about 1.5 to 2 inches across. Was it originally a silicious or calcareous sponge?

 

Does anyone know of an expert who is interested in undescribed sponges from Arizona/USA? I know of at least 3 other undescribed Arizona sponges.

 

Thanks,

 

John

 

[abyssunder]

I think, the distinction between them can be based on the material that forms the spicules. If the spicules are made out of calcium carbonate (calcite, aragonite), then the sponge is calcareous sponge, if the spicules are made out of silicon dioxide, then the sponge is silicious sponge. Also, it can be a complete silicification process of the fossil when the replacement of calcite by silica leaves a perfect representation of the fossil, but also can destroy it completely. I suppose your specimen is silica rich, but that not means it is a siliceous sponge (hexactinellid) from the origin.

 

Beautiful colors, BTW!

[Arizona Chris]

I found a very similar sponge at the intersection of Horton Creek and Tonto Creek.  It is still in matrix, maybe I need to plunge this one in the acid bath!

[Missourian]

Heliospongia is a possibility, particularly if the spicules form rows like this:

 

 

I've read that the spicules of Heliospongia were originally made up of opaline silica. Specimens collected in the Pennsylvanian rocks of my area, on the other hand, were either replaced by calcite, or silica (above image). 

 

Since these sponges are often the only silicified fossils in various beds, I think the original silica may have acted as a nucleus for subsequent silica mineralization, forming what could be called concretions. Example:

 

 

[fifbrindacier]

Nice colors, wonderful !

[abyssunder]

I'm pretty sure you have this document, John, but for those who haven't see it before, here it is.