advantageous because it allowed for the evolution of more effective mouth-parts for capturing and processing food. Insects are strongly cephalized, their brain made of three fused ganglia attached to the ventral nerve cord, which in turn has a pair of ganglia in each segment of the thorax and abdomen. The insect head is an elaborate structure made of several segments fused rigidly together, and equipped with both simple and compound eyes, and multiple appendages including sensory antennae and complex mouthparts (maxillae and mandibles). Cephalopods Cephalopod molluscs including octopus, squid, cuttlefish and nautilus are the most intelligent and highly cephalized invertebrates, with well-developed senses, including advanced 'camera' eyes and large brains. Vertebrates Cephalization in vertebrates, the group that includes mammals, birds, reptiles, amphibians and fishes, has been studied extensively. The heads of vertebrates are complex structures, with distinct sense organs (sight by camera-type eyes, olfaction by nostrils, taste by taste buds, balance & hearing by otic vesicle); a large, multi-lobed brain (three-part at least); and later, in jawed ones, teeth and, in tetrapods, tongue (teeth like keratinous structures and tongue arose independently in jawless lampreys).Cephalochordates like Branchiostoma (the lancelet, a small fishlike animal with very little cephalization), are closely related to vertebrates but do not have these structures. In the 1980s, the new head hypothesis proposed that the vertebrate head is an evolutionary novelty resulting from the emergence of neural crest and cranial placodes (thickened areas of ectoderm), which result in the formation of all senses outside of the brain. However, in 2014, a transient larva tissue of the lancelet was found to be virtually indistinguishable from the neural crest-derived cartilage (later bone, in jawed ones) which forms the vertebrate skull, suggesting that persistence of this tissue and expansion into the entire head space could be a viable evolutionary route to formation of the vertebrate head. Advanced vertebrates have increasingly elaborate brains. See also Noogenesis Organogenesis Phylogenetics References Evolutionary biology Evolutionary biology terminology