The Monk Calf and Papal Ass continued to play a role in German publications on monstrous births as the sixteenth century progressed. The latter half of the century saw the rise of publications that moved well beyond reporting singular, and in the main contemporary monstrous births, and towards a new genre called the wonder book. These collected together monstrous births and various other wonders and disasters across decades, centuries or even millennia. The Monk Calf and Papal Ass took a central place amongst a group of increasingly iconic monstrous births. The most important authors to produce illustrated German wonder books were Job Fincel and Konrad Lycosthenes, and their precursor Jakob Rueff, and they are the focus of this chapter. Negative and also apocalyptic rhetoric about monstrous births became still more deeply entrenched in this genre. The increasing number of cases circulating in print fostered an accompanying polemic of multiplicity as well as a desire to identify and single out emblematically bizarre new cases. Chief amongst these in the middle of the century was the visually demonic monster of Krakow, examined in some detail later in this chapter.

The attitudes of Rueff, Fincel and Lycosthenes towards the Monk Calf and Papal Ass are a useful introduction to these authors’ wider interest in monstrous births. In 1554, the Zurich physician Jakob Rueff included the Monk Calf in his book Ein schön lustig Trostbüchle von den empfengknussen vnd geburten der menschen (‘A Cheerful Consolation Book on the Generation and Birth of Humans’, Fig. 4.1). This creature was less a human-animal hybrid than a monstrous animal birth with exceptional qualities, although Rueff refers to it as a child (‘kind’) rather than an animal, presumably in an attempt to legitimize its inclusion in his book on human generation and birth. The illustration makes it appear rather smaller and less dramatic than it had in Lucas Cranach's version for Martin Luther.