Hyolithid Fossils
Phylum Hyolitha
Geological Time: Lower Cambrian
Size (25.4 mm = 1 inch): Hyolithid fossils are 25 and 20 mm; matrix is 130 mm across at widest point
Fossil Site: Pioche Shale Formation, Nevada
Fossil Code: INV21
Price: Sold
The
Hyolithids are an extinct group of problematic animals that appeared in
the lower Cambrian and persisted into the upper Permian. The taxonomy remains
in dispute, with some believing they belong to a separate disaapeared phylum,
and others a disappeared class of 
Mollusc. They had a long, conically-shaped,
closed shell,Phylum Hyolitha with a lid (operculum) covering the opening,
and a pair of long, horn-like outgrowths. The animal lived on the sea-bottom,
or partly buried. They reached their peak in the Cambrian and declined
thereafter. This plate has two larger and nicely colored Hyolithids. They
come from the famous, Lower Cambrian, Pioche Shale in Nevada where they
are
sometimes
found in
association
with Olenellid trilobtes. 
