Invertebrates are a diverse group of animals that includes over 30 phyla. Members of this group do not have a backbone, nor a bony skeleton. Fossil evidence indicates that early invertebrates first appeared about 600 million years ago during the Precambrian. Scientists have identified close to one million living species of invertebrates but this represents only a small fraction of the total number of invertebrates alive today, which could number as many as 30 million. Here you can browse pictures of invertebrates including jellyfish, ladybugs, snails, spiders, octopus, chambered nautiluses, mantis and more.