Centro Island
Land of endemism

Centro Island is the biggest cambiocenic island of Antarctica and, thanks to its north position, one of the warmest and richest. The island was ancestrally colonized by the few flying survivors of the END, like ground tyrants and eggpouchers. It was then colonized by small geotters and flightless birds thanks to rafting wood and later by rodents and lizards thanks to Aves ex Machina's introductions.
The arrival of new carnivores has caused a big die out of large ground tyrants, which evolved in a nearly predator-free environment: eggpouchers were the first vertebrate to take advantage of this situation, causing a final ecological turnover on the island.
After 4 million years, eggpouchers have become one of Centro's largest and ecologically fundamental vertebrates; among all, the herbivoo (Cuculirostris centralis) is the biggest and most widespread, living in the immense mediterranean lowlands of the island.
The cuckoo's ancestrality of this 70 kg bird is easily recognizable by its foot orientation, two pointing forward and the other two backward. Herbivoos are browsers that feed on low branches of trees and shrubs thanks to their elongated neck, which is half their total height.

Like all eggpouchers, the herbivoo is an ovoviviparous bird that retains the eggs in a sack of the oviduct. Chicks are born hyper precocial, capable of following their parents after a few minutes of the hatch, which enables them to avoid predators like terror eggpouchers  (Oculaves raptoria): because their size doesn't permit them to hunt large prey, these carnivorous eggpouchers have adapted to hunt any small-sized vertebrate, primarily rodents.
Despite maintaining a cuckoo's appearance, terror eggpouchers have evolved some new anatomical features, including a larger oviduct that can contain as many as 4 eggs simultaneously (twice compared to a classic ovoviviparous cuckoo). This adaptation has greatly increased the resilience of this species: the terror eggpoucher in fact can rapidly recover its population, which is greatly affected by the large demographic fluctuations of its prey. Centro Island is in fact located near the Fire Bridge, home to the most active volcanos of Antarctica; periodically large eruptions can often affect negatively the fauna and flora of this limited size island, which has developed in response to a very dynamic and resilient ecosystem. 

The largest animal of Centro Island is neither a bird nor a mammal, but a lizard:  the centrolossus (Insulacerta neoarchipelagos). Favored by the warm climate and lack of competition, this reptile has become a giant placid grazer of the dry forests of the island, reaching nearly 3 meters in length.
While not having a stomach as efficient as a rostrid, the low-energy intake of this species didn't lead to develop a more complex digestive system; evolution is not progression and if a certain adaptation is enough to survive, it doesn't need to become more advanced.