| Ptychopariid
                    Trilobite Fossils | 
                   
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                    | Family 
                        Alokistocaridae | Family 
                        Menomoniidae | Family 
                        Llanoaspididae | Family
                    Olenidae | 
                   
                    | Wheeler 
                        Formation, Utah | Weeks 
                        Formation, Utah | Weeks 
                        Formation, Utah | Lorraine
                    Shale, Lewis County, New York | 
                   
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                    | Family 
                        Alokistocaridae | Family 
                        Lonchocephalidae | Family 
                        Asaphiscidae | Family 
                        Ptychopariidae | 
                   
                    | Pierson 
                        Cove Formation, Utah | Weeks 
                        Formation, Utah | Wheeler 
                        Formation, Utah | Chisholm 
                        Shale, Nevada | 
                   
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                    |  Family
                        Olenidae | ? | Family
                          Olenidae | Family
                          Ptychopariidae | 
                   
                    | Trinity 
                        Bay, Newfoundland | Cranbrook,
                          British Columbia | Cordillera
                          Formation, Argentina | Marjum
                          Formation, Utah | 
                   
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