Here is a very large Elrathia from the Pierson Cove Formatiom.

This Elrathia marjumi from the Pierson Cove Formation does show the typical hook of the pygidal rim. But this specimen do have 13 thorax segments like a Elrathia kingi. The classical Elrathia marjumi has 12 thorax segments. The genus Elratia seems to be quite variable in the number body segments. It seems a other time that systematic dos not fit in numeric statistics.


Pierson Cove Formation is mostly equal to Wheeler and mostly Marjum Formations and represent a shallower environment.

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