Hidden Animals

Most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago.
Etymology
The word "animal" comes from the Latin word animalis (meaning with soul, from anima, soul). In everyday colloquial usage, the word usually refers to non-human animals. Frequently, only closer relatives of humans such as mammals and other vertebrates are meant in colloquial use. The biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects and humans.