This is a Utah Trilobite of the species Elrathia kingi  with a bite mark.
Usualy those trilobite injuries are interpreted as bite marks caused Anomalocaris praying on Elrathia kingi. This is a popular hypotheses because Anomalocaris is indeed known from the Wheeler formation and other predators simply not. However this species shows a picture book pathology of this kind.  In fact are this injures aren’t that rare on Elrathia, but usually they are not that nice develop. The Trilobite itself is about 18 mm long.

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