Trilobite with Preserved Anomalocaris Bite
Order Ptychopariida, Family Asaphiscidae
Time: Middle Cambrian
Wheeler Shale Formation, Millard County, Utah
from the Cambrian Wheeler Formation deposits of Millard County Utah
this is a detailed example of the trilobite Asaphiscus wheeleri.
These trilobites are often found with disarticulated or missing
free cheeks. This fine example is well-articulated, with a dark
black exoskeleton which contrasts well with the grey shale matrix
which derives its color from its high organic content. What makes
this one of interest is the fact that a section of the pleural is
missing, the result of the trilobite’s being bitten, presumably
by an Anomalocaris. Since there is no evidence for growth at the
edge, it was most likely the direct cause of death. Interestingly,
these bites are typically found on the right side of the trilobite,
indicating some preferred attack mode by the terror of the Cambrian.
Evidently the predator here was directionally-challenged, coming
in from the left of the hapless trilobite seen here.
Explosion Biota from Utah
fossil pictures to enlarge