Peters cycle at the end of the cosmic ray spectrum?

We investigate the degree to which current ultrahigh-energy cosmic ray observations above the ankle support a common maximum rigidity for all nuclei, often called a Peters cycle, over alternative scenarios for the cosmic ray spectra escaping sources. We show that a Peters cycle is not generally supported by the data when compared with these alternatives for the scenarios studied. We explore the observational signatures of non-Peters cycle scenarios, and the opportunities to explore both ultrahigh-energy cosmic ray source conditions, as well as physics beyond the Standard Model they present.