The second of the coordinate families into which Crane-like birds (Gruiformes) are divided comprises the Cranes proper, as well as the minor groups which are assumed, in the system of classification we are following, to be most closely related to them. It must be confessed, however, that the present grouping is not agreed upon by all ornithologists, but this simply illustrates another case of the difficulty experienced in arriving at a uniform classification of groups that are confessedly of close affinity. The selection of one set of characters as a basis for classification may give results quite different from those to be obtained with another set, and it thus becomes a matter of extreme difficulty to determine satisfactorily the characters to which most weight should be given. Suffice it to say that, all things considered, the present grouping is perhaps as satisfactory as any that can be devised in the present state of our knowledge, which is unfortunately far from complete, regarding many of the forms included.
The family is divided into three subfamilies, the Gruince, or true Cranes, the Aramince, or Courlans, and the Psophiince, or Trumpeters. The especially distinguishing marks will be set forth under each heading.