The hoatzin (Opisthocomus hoazin)

The hoatzin was originally described in 1776 by German zoologist Statius Müller. There has been much debate about the hoatzin's relationships with other birds. Because of its distinctness it has been given its own family, the Opisthocomidae, and its own suborder, the Opisthocomi. At various times, it has been allied with such taxa as the tinamous, the Galliformes (gamebirds), the rails, the bustards, seriemas, sandgrouse, doves, turacos and other Cuculiformes, and mousebirds. A whole genome sequencing study published in 2014 places the hoatzin as the sister taxon of a clade composed of Gruiformes (cranes) and Charadriiformes (plovers).