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Modern sponges such as the barrel sponge do not build reefs structure

Modern sponges such as this barrel sponge in the back of this image do not build reef structures.  However, chaetetids, sponge-like organisms found in the Pennsylvanian, did build reef-like structures.  At that time, reef-building scleractinian corals that are part of modern reefs did not yet exist.

New specimens are constantly being added to the collection.  These are referred to as 'accessions'.  This page tracks the collection of a chaetetid specimen.

The specimen is cleaned and imaged
Taxon: Chaetetes sp.
Age:  Pennsylvanian
Horizon:  Marble Falls Limestone
Location: Texas

this chaetetid was collected for NPL
Here is a similar specimen as it looked in the field.

At this site, chaetetid mounds are exposed in the bed of a creek. The location of the specimens are carefully mapped.

information concerning the specimen is added to the data base, iincluding a map location.

To get an idea of the size of this chaetetid mound, look for the blue handle of a geologist's hammer near the bottom of the image.  From head to handle, this hammer is about a foot long.

chaetetid mound

chaetetids in cross-section
The rock surface on the left shows a mass of chaetetid heads in cross-section.  The upper parts have been eroded away.  The partial specimen to the right is much larger.
an example with partial chemical alteration of the original structure

The living animal's skeleton was made of calcite, but parts of it were altered to silica by fluids flowing through the tiny pore spaces after the animal died and was buried.  We discovered that alteration using a simple hand lens and dilute HCl.

*Note: Chaetetids have been placed in several groups, some regard them as tabulate corals, but we are following the placement within the phylum Porifera, class, Demospongea.



Frequently used abbreviations: NPL  Non-vertebrate Paleontology Laboratory | TNSC Texas Natural Science Center | UTDGS Department of Geological Sciences | BEG  Bureau of Economic Geology | VPL Vertebrate Paleontology Laboratory | JSG  Jackson School of Geosciences | SUPPORT | VOLUNTEER | GLOSSARY

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