Keelback (70 - 77 MYH) by salpfish1 on DeviantArt (original) (raw)

When Antarctica melts, gulls will colonize it. They'll diversify like Darwin's finches with more time to evolve. The keelback will descend from brood parasites, which don't just use their wings to fly, but also to grab other chicks. They'll become neotonous, using their wings to climb like monkeys and infect other nests.

Antarctica will freeze again, and its grass forests will die. The monkey-like birds will have to crawl with their wings behind their back. To protect their soft belly, the keel will grow to cover them. This is how the keelbacks will evolve. Without any nests to parasitize, they'll be forced to carry their eggs like marsupials. They'll browse on any vegetation they can find, mostly tough grass descendants with interlocking, spicule-like phytoliths.

When Antarctica warms up a second time due to continental drift, Antarctica's keelbacks will rival Australia's marsupials in diversity. They'll fill the niches of turtles, predators and insectivores, only decreasing in diversity when Antarctica collides with the other continents to form Pangea Ultima.