What government was Pliny the elder living under according to Aristotle's classification system?

Pliny the Elder lived during the Roman Empire, which can be classified as a form of monarchy under Aristotle's classification system. Although the Roman Republic existed prior to this period, by Pliny's time, the empire was characterized by autocratic rule, particularly under emperors like Vespasian and Titus. This form of government, while encompassing elements of oligarchy and democracy in its earlier stages, predominantly reflected the centralized power of a single ruler, aligning with Aristotle's definition of monarchy.