Phylogenetic analysis used to identify the set of novel genes unique to songbirds (oscine passerines). (A) Schematic diagram summarizing phylogenetic relationships among organisms included in genomic analyses, not to scale. Full details on genomes included in these analyses are reported in main avian phylogenomics and comparative genomics papers [34, 35]. (B) Simplified schematic of the Zebra finch nuclei specialized for vocal learning and their connections. Red projection: the posterior vocal motor pathway for vocal control, originating in HVC, in yellow, continuing to RA, in orange, to the hindbrain vocal motor nuclei, in black. Blue projection: the anterior forebrain pathway for vocal learning, originating in HVC, which projects to a set of interconnected nuclei (Area X, LMAN, DLM) analogous to mammalian cortical-basal ganglia-thalamo-cortical loops for somatosensory learning. Abbreviations: DLM, medial part of the dorsal lateral nucleus of the thalamus; LMAN, lateral magnocellular nucleus of the anterior nidopallium; HVC, proper name; nXIIts, tracheosyringeal portion of the hypoglossal nucleus; PAm/RAm, nucleus para-ambiguus/retroambiguus; RA, robust nucleus of the arcopallium.