Complex sentence: Saints Mark and Marcellian ("Marcus and Marcellianus") were martyred at Rome under Diocletian towards the end of the third century, most likely in 286.
Split into simpler sentences: Saints Mark and Marcellian ("Marcus and Marcellianus") are venerated as saints. Their legend states that they were martyred at Rome under Diocletian towards the end of the third century, most likely in 286.