Question

use the following cladogram to answer the questions below.
amphibians mammals reptiles turtles crocodiles avian dinosaurs birds
four - limbed
fetal development within a fluid - filled sac
two holes in each side of their skulls
skulls with long, narrow snouts and teeth set in sockets
upright stance, with legs perpendicular to their body
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part 1: which ancestral traits do both mammals and birds share? support your answer with data from the cladogram.
part 2: which derived traits do birds have that the mammals do not have? support your answer with data from the cladogram.

Explanation:

Part 1: Ancestral traits are inherited from a common ancestor. Mammals and birds share the trait "four-limbed" (from the most basal common node) and "aerial development within a fluid-filled sac" (from the node linking their lineages).
Part 2: Derived traits are unique to a lineage. Birds have "upright stance, with legs perpendicular to their body" (from the node shared with avian dinosaurs, not mammals) and "skulls with long, narrow snouts and teeth set in sockets" (from the node above the two-hole skull trait, not present in mammals).

Answer:

Part 1: Four-limbed; aerial development within a fluid-filled sac
Part 2: Upright stance (legs perpendicular to body); skulls with long, narrow snouts and teeth in sockets