 The vertebrate lineage represents just one of approximately 34 known phyla — ancient lineages of animals characterized by differences in fundamental anatomical organization and the developmental processes that generate it. Each of these phyla is derived from a relatively simple state (i.e. few tissue types and a minimal central nervous system with limited sensory capacities). Hence, the invertebrates such as cephalopod mollusks (e.g., octopi and squids) and arthropods (e.g. crustaceans, insects and spiders), that are complex enough to attract the attention of those interested in animal consciousness, evolved their complexity independently from vertebrates, and in the case of cephalopods and arthropods, independently from each other. 