Hyolithid Fossils
Phylum Hyolitha, or Phylum Mollusca, Class Hyolitha
Geological Time: Lower Cambrian
Size (25.4 mm = 1 inch): Largest Hyolithid is 24 mm; matrix 100 mm at widest point
Fossil Site: Pioche Shale, Nevada
Fossil Code: INV20
Price: $25.00
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, 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 Hyolithids. They come from the
famous, Lower
Cambrian, Pioche Shale in Nevada where they are sometimes found in
association
with Olenellid trilobtes.
