Here is a nice and rare trilobite of the species Elrathia marjumi from the Pierson Cove Formation of Utah.
Elrathia marjumi is much rarer than Elrathia kingii and differs from it by the fused pleural segment in the pygidium. This segment does form a small spike on the frontal flank of the tail.
In addition, Elrathia marjumi often tends to have 14 body segments. However, it should be noted that the genus Elrathia has a certain variability in the number of body segments. For Elrathia kingii, there are typically 13 pleural segments. Also E. kingii time a certain variability of Holaspids (adults) specimens. In addition, any specimen that does not yet have the typical number of pleuras could automatically be interpreted as a late Meraspis stage. How ever this specimen of Elrathia marjumi has 13 pleural segments but can’t be considered as a Meraspis strage with its 36 mm in length.
Pierson Cove Formation is mostly equal to Wheeler and mostly Marjum Formations but represent a shallower environment. The matrix is a fine siltstone which is comparatively challenging in preparation. |
