Imperium naturæ C. Linnaeus, 1758 - nature
   Mundus Plinius - physical world
     naturalia - natural bodies
       Regnum Animale C. Linnaeus, 1758 - animal kingdom see Kingdom Animalia Linnaeus, 1758
         Class Aves Linnaeus, 1758 - birds see Subclass Aves Linnaeus, 1758
           Order Anseres Linnaeus, 1758 see Suborder Anseres Linnaeus, 1758
             Genus Alca Linnaeus, 1758
               1 Alca torda Linnaeus, 1758 - razorbill
               2 Alca impennis Linnaeus, 1758 see Pinguinus impennis (Linnaeus, 1758)
               3 Alca arctica Linnaeus, 1758 see Fratercula arctica (Linnaeus, 1758)
               4 Alca lomvia Linnaeus, 1758 see Uria lomvia (Linnaeus, 1758)
               5 Alca grylle Linnaeus, 1758 see Cepphus grylle (Linnaeus, 1758)
               6 Alca alle Linnaeus, 1758 see Alle alle (Linnaeus, 1758)