Scientists estimate that there are almost 9 million species of animals in the world, yet 86 percent of land animals and 91 percent of sea animals have yet to be identified. It would take an astounding 1,200 years and the work of more than 300,000 taxonomists to describe the remaining uncategorized species. Unfortunately, many will become extinct before they can be identified. Even among known animals, there are many species that people have never heard of. Here's an introduction to five animals you might not be familiar with, but are definitely worth knowing.