Figure 6

Implications of the current findings for the evolution of the arthropod brain. The brain of the last common ancestor of Onychophora and Arthropoda was composed of the protocerebrum and deutocerebrum whereas the tritocerebrum, as part of the brain, evolved in arthropods (chelicerates, myriapods, crustaceans, and hexapods). The phylogenetic position of Myriapoda is unresolved [42, 63]. Double lines for Crustacea indicate that this group might not be monophyletic [64].