Cranial symmetry in baleen whales (Cetacea, Mysticeti) and the occurrence of cranial asymmetry throughout cetacean evolution

摘要: Odontoceti and Mysticeti (toothed baleen whales) originated from Eocene archaeocetes that had evolved terrestrial artiodactyls. Cranial asymmetry is known in odontocetes can hear ultrasound (>20,000 Hz) has been linked to the split function of nasal passage breathing vocalization. Recent results indicate also asymmetric crania. Their directional hearing water, although frequencies are still under debate. Mysticetes capable low-frequency infrasonic (<20 assumed have symmetric This study aims resolve whether mysticete crania indeed cranial symmetry plesiomorphic or secondary. shape was analyzed applying geometric morphometrics three-dimensional (3D) models fossil modern mysticetes, archaeocetes, artiodactyls, odontocetes. Statistical tests include analysis variance, principal components analysis, discriminant analysis. Results suggest difference reflects general trends cetacean evolution. Asymmetry includes significant fluctuating asymmetry, latter being very small. Mysticete as those artiodactyls without differences within Mysticeti. Odontocete more asymmetric. These (1) all mysticetes crania, (2) archaeocete not conspicuous most skull but may yet be rostrum, (3) an odontocete specialization, (4) likely related echolocation than hearing.