from Utah's Weeks Formation
Nephalicephalus beebiTrilobites Order Ptychopariida, Suborder Ptychopariina, Superfamily Ptychoparioidea, Family Menomoniidae Weeksina unispinaTrilobites Order Ptychopariida, Suborder Ptychopariina, Superfamily Ptychoparioidea, Family Cedariidae Menomonia semeleTrilobites Order Ptychopariida, Suborder Ptychopariina, Superfamily Ptychoparioidea, Family Menomoniidae Geologic Age: Middle Cambrian Also see: American Trilobites |