Hyolitha, Orthotheca

• Orthotheca belongs to an extinct phylum called Hyolitha. Members of this group are so unlike other animals they are placed in their own phylum.

• Hyoliths were small animals, generally less than four centimeters (1.5 inches) long, with a conical shell. The mouth was located at the large end of the shell.

• Hyoliths lived on the seafloor and probably filtered particles from the water.

• Orthotheca may have anchored itself in the substrate to maintain a vertical position for feeding.

• Some other hyoliths had a pair of small leg-like structures that held one end of their shell above the substrate to facilitate feeding.

• Hyoliths are found in Paleozoic layers but have not been found in sediments above the Permian layers.

• This specimen was collected from the Spence Shale in Idaho.