Sentence:  [P]erhaps the shadowy fetials were never actually an independent priesthood but were senatorial priests assigned diplomatic functions. If fetials were originally senators, this would explain the parallel <WSD>fetial</WSD> and senatorial function in "international relations" and account for the continuity between fetials and later senatorial legates. 
Meaning of the word marked with <WSD> tags:  Of or relating to a fetial (member of the Roman college of priests who acted as representatives in disputes with foreign nations);  ambassadorial, heraldic.