Middle Cambrian

Pioche Formation

Pioche, Lincoln County, NV, USA

Two very fine 0.25 inch hyolithids on 2.5 x 1.5 inch shale.

Hyolithid.

Hyolithids are shelled invertebrates of uncertain classification though the latest research places them perhaps related to brachiopods.  They reached their greatest abundance and diversity during the Cambrian but suffered greatly during the mass extinction at the end of that period.  The group went into decline but still managed to survive into the Permian before becoming extinct.