Rare Agnostid Trilobites Association Plate

Order 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.

Ptychagnostus michaeli, with its five spines, is one of the rarest agnostids found in the Marjum Formation, and only recently have good specimens been found. The P. cuyanus is the most common of the agnostids and the H.hypagnostus is of moderate rarety. In all, a very nice Cambrian trilobite association plate with three species and two families represented.