Cranes and their relatives the limpkins and trumpeters are fairly closely related members of the order of birds (Gruiformes) that also includes rails, gallinules, coots, and other marsh-adapted birds. Cranes, limpkins, and trumpeters are usually included within a superfamily, Gruoidea, although at least one recent authority (Cracraft, 1973) has suggested that the three groups all be included within a single family, Gruidae. However, traditionally only the cranes have been included within the Gruidae, and only the cranes will be dealt with in detail in this book. Nevertheless, the limpkins and trumpeters must be considered if the evolution of cranes is to be discussed, and thus it is perhaps desirable to define each of these three groups in a semiformal way, so that their similarities and differences are at once apparent.
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