While this main image depicts a very early naturalist simply observing a lion, two additional smaller images depict animals that raised problems of classification. The Starfish, sometimes difficult to appreciate as an animal, seemed to be an invertebrate but wore its skeleton on the outside (actually, a spiny skin). Starfish appeared in many different places within various schemes of classification. When evolutionary descent became the accepted criterion, their precise place depended on a very problematic record of fossil evidence.