Shared Derived Traits
Their appearance consists of a narrow band that runs in an upside down u-shape on their chests and a white band on their beaks. They also lack feathers on their legs and face. Unique behavior traits are that they have loud donkey like braying calls and they nest in burrows.
Shared Ancestral Traits
Wings modified into flippers, with very flat bones and the wrist and elbow joints fused. Their bones are solid to decrease buoyancy. Increased density of feathers. Countershading for camouflage with white under bellies and black backs. Legs positioned as far back as possible. Stiff and springy feathers to trap air while diving.
Figure 1.3: Phylogenetic tree of related neoaves
Kinzey, W.G. (1997). New World Primates, Ecology, Evolution and Behavior. New York: Aldine de Gruyter.