#horn.animal_material  the material (mostly keratin) that covers the horns of ungulates and forms hooves and claws and nails
  supertype:  #animal_material  material derived from animals
  substance:  #keratin
  subtype:  #whalebone__baleen  a horny material from the upper jaws of certain whales; used as the ribs of fans or as stays in corsets
  subtype:  #tortoiseshell  the mottled horny substance of the shell of some turtles

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