A field guide to mesozoic birds and other winged dinosaurs

Cathayornithiformes
The “Cathay birds” probably include two groups. The ‘cathayornithids’
are a group of relatively primitive enantiornitheans which are
united primarily by primitive characteristics (plesiomorphies). They may
therefore not represent a natural group, but because they are superficially
similar in appearance, they are placed together here for convenience. Some
phylogenetic analyses have found these to represent a grade which gave rise
to the avisauroids (Cau & Arduini 2008). Cathayornithids generally had
wishbone anatomy consistent with gliding or flap-gliding flight.
The avisauroids (“bird lizards”), possible advanced members of the
cathayornithiformes, were likely specialized perching birds, well adapted
to life in the trees. These were probably generally predatory and similar
to modern raptors in behavior. As the name suggests, avisauroids were
originally thought to be close relatives of the deinonychosaurs rather than
enantiornitheans, and even some recent analyses have yielded this result
(Kurochkin & al. 2011), but those have been criticized by other researchers
(Cau 2011). Only some primitive avisauroids are known from fossils
preserving the skull. While one of these (Cuspirostriornis houi) had a somewhat
pointed snout, the premaxilla was full of teeth and there is no evidence
that this or any other enantiornithien species, save Gobipteryx minuta, had
beaks.
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