After your investigation of five Cambrian animals, it should be clear that you can’t judge a fossil by first impressions. Paleontologists had a tough time classifying many of these Cambrian animals. Some of the animals you studied were unfamiliar, but turned out to be arthropods (Sanctacaris, for example, was a chelicerate). Others looked like one animal, but turned out to be another (Pikaia, for example, looked like a worm, but was actually a chordate). And the characteristics of animals like Opabinia revealed that they didn’t belong to any group alive today.