Ptychagnostus atavis Agnostid Trilobites

Ptychagnostus atavus

Order Agnostida, Suborder Agnostina, Superfamily Agnostoidea, Family Ptychagnostidae

Geological Time: Middle Cambrian

Size: 3 mm - 4.5 mm

Fossil Site: Lower Wheeler Formation, Millard County, Utah

Ptychagnostus atavis Agnostid TrilobitesOrder Agnostida comprises trilobites that appeared in the Lower Cambrian, became widespread and then declined to become rare in the Ordovician prior to their complete extinction by the end of the Ordovician. They are so unusual that some experts have suggested that one of the two suborders, Agnostina, should not even be included in Class Trilobita. Believed plantonic, they often lacked eyes, and their cephalon and pygidium are of essentially the same size.

This plate coming from the Middle Cambrian of Millard County, Utah contains 16 specimens of the species Ptychagnostus atavus.

click fossil pictures to enlarge

Ptychagnostus atavus

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