“…Cetacean brains are thought to have numerous features that deviate from general mammalian trends, including a thin and highly laminated cortex, extreme gyrification, low neuron density but high synaptic density, unique neuronal cell types, and small hippocampi that lack adult neurogenesis (Breathnach, 1960;Butti et al, 2015;Eriksen & Pakkenberg, 2007;Haug, 1987;Huggenberger, 2008;Marino, 2002Marino, , 2007Morgane, Glezer, & Jacobs, 1990;Oelschläger & Oelschläger, 2009;Patzke et al, 2013;Poth, Fung, Güntürkün, Ridgway, & Oelschläger, 2005). Cetaceans also show a high degree of variation in several neural traits, including cerebellar size and cerebral cytoarchitecture (Hof & Van Der Gucht, 2007;Marino, Rilling, Lin, & Ridgway, 2000;Ridgway, Carlin, & Alstyne, 2018;Ridgway, Carlin, Alstyne, Hanson, & Tarpley, 2017;Ridgway & Hanson, 2014).…”