Terrariders and hoofpoles
An infinite clash

The arrival of hoofpoles has significantly altered the biodiversity of ground birds, filling various vacant niches and outcompeting other species. Some hoofpoles have remained relatively small, while others rapidly diversified, pushing their bodies to the upper limit for airborne birds. An exemplary case is the elegant hoofpole (Gigadactyla circumrostri), which can weigh up to 50 kg and boasts a wingspan of 3 meters. Despite their substantial size, their wings are proportionally modest, not for flying but just for fluttering, providing enhanced acceleration during running or enabling jumps as high as 4 meters.

Cursorial birds were among the first affected by the radiation of hoofpoles: the ability to both fly and run and their specialized body plan became crucial advantages for these birds, in contrast to Antarctic flightless birds, like terrariders. While terrariders never experienced a significant species explosion like the brumbles, they retained a widespread distribution across the entire Biancocene. However, their dominance is dwindling rapidly, leaving only one species of terrarider in Antarctica. This surviving species was able to withstand the hoofpole radiation by increasing its size well beyond the weight limit for flying birds, reducing food competition with other herbivores.
This survivor is known as the boundless terrarider (Ramphielephas nivalis) and ranks among the largest birds on the icy continent — weighing over 300 kg and reaching heights of up to 4 meters — as well as one of the most beautiful, thanks to its striped and marbled pattern. Anatomically similar to its cambiocenic ancestor, it retains a foot wit two digits, a long neck for diverse feeding, and a lightweight build enhancing speed. While not as agile as hoofpoles, the boundless terrarider can achieve speeds of 50 km/h due to its remarkably long tarsus—quite impressive for its size. However, this extreme feature brings challenges, causing stress and increased bone fracture risks due to the leg's struggle to support the bird's weight.

A relatively common pathology (10% of newborns) among terrariders is bow leg syndrome, resulting from rapid size growth outpacing leg strengthening, leading to locomotion difficulties or an inability to run. Despite surviving alongside hoofpoles, the rapid gigantism of terrariders that doubled their size in just a million years has resulted in significant health problems. A similar situation can be observed in humans, who experience a high and frequent number of back pains and shin splint, possibly due to the relatively rapid evolutionary trend that led to our bipedalism.
Despite these challenges, terrariders are not uncommon. They thrive in the most fertile trample-steppe areas, feeding on grasses, forbs, and shrubs.
Only time will determine the destiny of this giant yet delicate bird.