The Spiral in the Tusk of the Narwhal

Michael C.S. Kingsley, Malcolm A. Ramsay


The spiral in the tusk of the narwhal has been fancifully, but never satisfactorily, explained. Spiral growths are common in the animal kingdom and share the feature of having straight axes. A curved tusk would hinder the narwhal swimming; a spiral mode of growth ensures overall straightness even if the tusk grows irregularly. The need to keep the tusk straight completely and satisfactorily explains the spiral.

Key words: Monodon monoceros, dentition, morphology, asymmetry


Animal anatomy; Dentition; Narwhals; Canadian Arctic waters

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