Two Sponge holdfasts
found in St. Louis County, Missouri

Pennsylvanian - images 1-4
Mississippian - image 5

Altamont Formation
St. Louis Louis County, Missouri

Sponge holdfast (Pennsylvanian) 1

Sponge holdfast (Pennsylvanian) 2

Sponge holdfast (Pennsylvanian) 3

Sponge holdfast (Pennsylvanian) 4
Sponge holdfast

Warsaw Formation
St. Louis Louis County, Missouri

sponge holdfast (Mississippian) 5
Mississippian Sponge holdfast

Barry Sutton

Thanks to Steve Pavelsky for the identification

Viewer Comments #1

These are sponge holdfasts. I have one too from the Warsaw fm.
They are not uncommon. Silica/pyrite/marcasite replacement common.
Steve Pavelsky

Viewer Comments #2

Very interesting specimen. Identification as a sponge holdfast
is reasonable. Note the long straight spicules. This is a variant.

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Because the images of the Pennsylvanian specimen are also featured on the
St. Louis Pennsylvanian Fossils of the Altamont Formation
web site, permission is required to use the images in other publications.

Barry Sutton

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