How does one establish the authenticity of nature? In this paper, I investigate this puzzle in the decades around 1600. Across early modern Europe, ancient artefacts were treated with growing suspicion. Fake coins and inscriptions flooded the antiquarian market, and forgeries were ubiquitous in reputable collections. Within learned circles of natural history, the fossilized remains of extinct creatures fuelled a similar crisis of authenticity. Some naturalists claimed that extinct species represented “genuine animals” (vera animalia), yet others dismissed these as bad imitations or “jokes” (lusi) that were not to be taken seriously. This paper examines the intertwined discourse of extinction and authenticity through two contemporary case studies: the apothecaries Ferrante and Francesco Imperato; and the botanist Fabio Colonna. It suggests that naturalists adopted methods of authentication from antiquarians, borrowing methods of empirical comparison and textual verification.