This is a rare Hurdiid anomalocaridid of the species Pahvantia hastate. In the Literature are these Anomalocarididae are also referred as Hurdia c.f. triangulate Walcott, 1912.
The specimen is preserved as a reddish oxide stain. The specimen is incomplete as you can see. What is remarkable are the apparent surface details. The stripes, or wrinkles, (as the academics call them) run the center length of the specimen. It appears to be the top head shield as shown in artistic representation. This is a remarkably rare find which I discovered in large old collection of Utah fossils recently acquired.The identification was confirmed by two well respected paleontologist.
"Hurdia triangulata an anomalocaridid, and is usually considered to represent either a basal stem-lineage euarthropod (e.g. Daley et al., 2009), a member of the crown-group arthropods (e.g. Chen et al., 2004), or a sister group to the arthropods (Hou et al., 2006).
Pahvantia or Hurdia are relative newcomers to the anomalocaridids. Although isolated parts of its body were first identified in the early 1900s, no affinity could be determined until the description of whole body specimens by Daley et al. in 2009.