To the modern eye, Ulisse Aldrovandi’s work presents an evident discrepancy: it offers elements which have been interpreted as first steps in modern biology. Among them, the illustrations immediately draw attention, as they prove a new way of observing and describing nature, contrasting with the medieval symbolic approach of plants and animals. But some of the illustrations are obviously wrong, imaginary, or clumsy. Generally, modern history of sciences has rejected these as errors, arguing that their presence was due to the immaturity of a boring new science. This paper aims to present another way of considering the coexistence of contradictory elements in Aldrovandi’s scientific discourse: these elements must not be judged and classified from our modern point of view. They testify to the existence of a mainly different and polymorphic, but coherent representation of nature.