Tuzoia Decorated Phyllocarid Fossil from Nevada

Description: This unusual fossil is an example of a rarely-seen Phyllocarid known as Tuzoia that comes from the Comet Shale Member of the Pioche Formation of Nevada. Tuzoia Phyllocarids are classified as bivalved crustaceans, and are known for their distinctively-reticulated carapace. This deposit spans the transition of Early to Middle Cambrian which saw the extinction of the Olenellid trilobites. It is just younger than the comparable material from the Chengjiana Biota of Yunnan Province, China and just older than the Burgess Shale Fauna of British Columbia, Canada. The genus is known from the Burgess Shale and from Early/Middle Cambrian deposits of Utah. Species are largely distinguished by the presence and placement of spines on the carapace. Few examples of the genus are known from more than the carapace, as seen here, with its intricate polygonal decoration. Because of the manner of preservation, specimens are often fairly faint, as is the case here. There is a partial trilobite in the upper right corner of the first photograph. It is known as Eokochaspis nodosa, a member of the order Ptychopariida, family Ptychopariidae.