The fall of the Triumvirate

Like the Roman one, the Antarctic Triumvirate was not destined to last forever. At the first environmental change, some species would have taken the opportunity to win the competition against others. And that's what happened, during the Biancocene: the exacerbation of global temperatures has quickly led to a sharp collapse of the diversity of brontosparrows, relegated to the warmest areas of the continent, to the advantage instead of rostrids and some species of rodents. Now brontosparrows are virtually extinct from Antarctica, with a single relict species surviving in the warm coastal belts of the Reliquia forest. It is called fuzzy brontosparrow (Dinopasser minutus), due to the presence of thick plumage in winter, which is unusual for thermophilic species such as brontosparrows. The species has managed to survive to this day only thanks to its generalist diet: despite this, the progressive reduction of the relic forest and the competition with other competitive species, like armadrails, he’s slowly leading this big bird through the extinction vortex. The age of the brontosparrows is already over, but this is always how it works after all: an overabundance of clades diversifies after catastrophic events, which however gradually reduces with the advent of more stabilized and competitive fauna associations.

The brontosparrow are not, however, the only dead tracks of Antarctica: even the large ragos, once widespread in the tropical-temperate belt of the continent, are now limited to a single species called Reliquia (Ultimimegadon longicorpi), which gives its name to the homonymous forest of the Antarctic peninsula. Reliquia is not directly related to cambiocenic titaragos but rather derives from another clade that inhabited relatively colder climates. The species also has a different diet, more folivorous than frugivorous, due to the lack of a continuous presence of fruits throughout the year. They are also much more arboreal, being also of lesser size, allowing them to climb large trees even in adulthood.  In order to camouflage from the various predators of the forest, Reliquia possesses a counter-shading pattern, with a black/grey back and a white/cream belly:  in fact, despite being relatively large, the ongoing process of aridification of its forests has caused the arrival of a new vicious predator adapted to the open landscape, from which Reliquia can't easily escape or defend.
Although the dynasty of Reliquia is over, the same cannot be said for ragos in general: this group of omnivorous geotters is still well diffused, with some species adapted also in the treeless environments of the tramplesteppe. Their legacy, unlike brontosparrows, is not over yet. For now.