When comparing the brain of a typical shark like the Spiny Dogfish and a highly derived one like the Great Hammerhead, the differences are obvious. The Great Hammerhead has an enlarged telencephalon (embryonic forebrain) and a highly foliated cerebellum reminiscent of a mammal, whereas the dogfish has a smaller telencephalon and a smooth undifferentiated cerebellum. Hammerheads also have a unique head among sharks in that the olfactory and optic regions are expanded laterally. Research suggests that these differences most likely evolved as a result of a combination of locomotor abilities, complex social behaviours, sensory-motor integration and prey capture.
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brain evolution, fishes, sharks, nervous system, brain, embryology |
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