Odontoceti - Toothed Whales
This group includes both the Sperm Whale and its Pygmy and Dwarf relatives. The species have in common a spermaceti organ or 'case', which is fitted into a depression on the toothless upper jaw, an underslung lower jaw with large teeth and a comparatively simple air sinus system. There are two openings to the nasal passage divided by an external central septum but these are internal.
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