Morphology

Cuculiformes are made of the Families Cuculidae, Musophagidae, and Opsithocomidae.  The admittance of Musophagidae in the Order Cuculiformes is disputed by many taxonomists because of their distinct differences. The Sibley-Ahlquist taxonomy also has called the inclusion of Opsithocomidae into the Cuculiform order into question.

Turaco from the Musophagidae family


Hoatzin from the Opsithocomidae family

Cuculidae, the primary family of the Cuculiformes, are the only family found in North America. Family Cuculidae, primarily made up of cuckoos have distinct morphological characteristics that are shared by the species in the family. Morphologically, these birds are all medium sized, with slender bodies and zygodactyl toes. The arboreal species are considered to have more slender bodies than the heavier species that are less arboreal. Their wings and tails are fitted to their lifestyles, and long tails are used to steer for arboreal species.


Most species are insectivores and prefer insects such as caterpillars. These species prefer to "process" their food by rubbing the insect against branches and stones before consuming the insect to ensure that they are not eating any hairy substances the insects may have for protection against predation. 

 Sources:
Wikepedia
Tree Of Life