def get_ar_only_dams(american_rivers_df, dam_science_df):
    """
    Description
    ------------
    Finds dam removal records in American Rivers database that are not documented in the 
    USGS Dam Removal Science Database.
    
    Parameters
    ------------
    american_rivers_df: pandas dataframe of full American Rivers Database
    dam_science_df: pandas dataframe of full USGS Dam Removal Science Database
    """

    ar_in_science = dam_science_df['AR_ID'].dropna().to_list()
    ar_only_dams = american_rivers_df[~american_rivers_df['AR_ID'].isin(ar_in_science)]
    return ar_only_dams