Order Ptychopariida, Suborder Ptychopariina, Superfamily Ptychoparioidea;
Time: Middle Cambrian
Site: Marjum Formation, Millard County, Utah
truely fine example of this species. The Elrathia marjumi comes
from the formation directly on top of the layer containing the common
Elrathia kingii, and may be a direct descendant.
differences are small. The main difference is two short stubby spines
(comapred with E. kingii) on the pygidium, just below the last thorasic
segment. But even in the closeup its hard to see. This species is
found higher in the Cambrian strata, than the 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