Choice Elrathia Marjumi Trilobite
Order Ptychopariida; Family Ptychopariidae
Time: Middle Cambrian
Marjum Formation, Drum Mountains, Utah
Presented is a very large adult specimen of Elrathia marjumi. The
preservation is superb and the prep work first rate. The specimen
sits comfortably on a thick and solid plate. The species derives
its name from the formation directly on top of the layer containing
the common Elrathia kingii, and may be a direct descendant.
The differences are small. The main difference is two short stubby
spines (compared with E. kingii) on the pygidium, just below the
last thoracic segment. But even in the closeup it is hard to see.
This species is found higher in the Cambrian strata, than E. kingii,
and the marjumi are found in matrix that is much harder than that
of kingi, making preparation much more difficult.
fossil pictures to enlarge
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