Gruimorpha

Very diverse, possibly paraphyletic group near the base of the second great Neornithine radiation. Bill long and thin; 2 carotid arteries; crop absent; wings usually rounded and long; legs long; hallux absent or elevated; aquatic forms have lobate, not webbed, feet; sexual dimorphism infrequent; elaborate "dancing" behaviors, generally related to pair-bonding (monogamy is typical); territorial defense and courtship are largely vocal; very wide ecological and trophic range; migration uncommon.

Moderate-sized, foot-propelled lobe-toed divers. 1 carotid; poorly developed carinae and so weak flyers, or nearly flightless; wings short with thin bones; 12 primaries, 7 attached to metacarpus; 5th secondary absent; extremely fast, agile divers, with legs set well back on body and encased in body wall to the ankle; patella-like process on knee, together with strong (cnemial?) process of tibia; reduced tail feathers; oil gland with two openings; caecae present, but reduced; normally inhabit still water areas; monogamous, with elaborate pair-bonding behaviors; floating nests.

Moderate-sized (0.1-1.0 m) nocturnal (or crepescular) hunters. Large head; large, forward-facing eyes; eyes encased in bone tube & almost immovable; facial disk around eyes; enhanced night vision, but may be color blind; pupils dilate independently; enhanced hearing with moveable operculum to focus sound; other enhancements poorly understood (e.g. asymmetrical ears); hooked beak; highly mobile neck with 360 degrees rotation; short tail; long, rounded wings; nap on feathers makes flight soundless; large, strong feet with sharp talons; pes IV reversible; exclusively carnivorous, largely insects and rodents; rarely extensive flight or walking; very wide variety of habitats; vocal, with wide variety of sounds; generally not nest builders, but use natural cavities or abandoned nests.

Large mouth with very large gape; large eyes; bill usually not raptorial; wings medium to long; legs short, especially tarsometatarsus; feet small (except oilbirds); claws usually not raptorial; soft plumage, cryptic coloration; males frequently with elongated tail or wing feathers as display; crepescular; some have echolocation; typically feed on insects or fruit (oilbirds); young very slow to develop; vocal, with distinctive non-musical songs and mechanical noises; no characteristic mating, migration or nesting pattern; torpor and even hibernation known in some forms.

head crests; feather tracts absent; pamprodactyl foot; nondescript color; "fluffy" plumage; very long tail; mainly frugiverous; short legs; adept at climbing and hanging vertically or even upside down; gregarious.