The Archaeotrogonidae actually seem to be Cypselomorphae and related to nightjars and hummingbirds, either as a basal lineage or as a distinct but entirely extinct family.
While only the latter study recovered monophyly of the Cypselomorphae (see below) within Metaves, the former was based on only a single locus and could not resolve their relationships according to standard criteria of statistical confidence.
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The Aegothelidae (owlet-nightjars) with about a dozen living species in one genus are apparently closer to the Apodiformes; these and the Caprimulgiformes are closely related, being grouped together as Cypselomorphae
This potoo is a large cypselomorph bird related to the nightjars and frogmouths, but like other potoos it lacks the bristles around the mouth found in the true nightjars.
The subdivisions of the latter are still not well resolved, but several monophyletic lineages have been proposed, such as the Mirandornithes, Cypselomorphae or Metaves and Coronaves.
This, the caprimulgiform lineage(s), and the Apodiformes, are postulated to form a clade called Cypselomorphae, with the owlet-nightjars and the Apodiformes forming the clade Daedalornithes.
This is unsupported by more recent research (see Cypselomorphae for details), but the relationships of the owls in general are still unresolved.
This is unsupported by more recent research (see Cypselomorphae), but the relationships of the owls in general are still unresolved.