One of the oldest books about animals is the Historia animalium, by the Swiss naturalist Conrad Gesner (1516-1565). It's really a collection of five books, published from 1551 to 1558, that include animals both real and imaginary (e.g., unicorns and sea monsters). The image above is a page from volume 3, birds, and one of several scanned by the National Library of Medicine and now made available online along with other rare, historical texts from the collection.
Check out the entire collection of Pictures of the Week on our Facebook fan page.
( Hat tip: Pharyngula)