Deriving from burrowing icekissers, the bellydrugger (Fossapteryx insectophaga) is the most aberrant penguin that ever existed and the most fossorial bird of Antarctica. It's the first and only member of the so-called Cuniculapertidae family.
While icekissers still maintained a strong relationship with water, bellydruggers have become completely terrestrial. They have a horizontal orientation of the body, like a quadrupedal animal, but they are not truly quadrupedal: wings are very strong but they are placed laterally (like most reptiles), making it difficult for them to move properly on alternate locomotion. Wings are mainly used to dig up the soil, in search of invertebrates, similar to a mole. While all penguins ancestrally lack their alula, bellydruggers have developed a false cornified thumb similar to pandas, which helps at moving underground.
Feet are strong but very short and they are not able to sustain alone the entire weight of the animal, which prefers to move by drugging their belly in their tunnels. Feet are mainly used as propulsion, while tiny caudal feathers work as a broom to move away debris. Plumage cover is dense and very short, with remiges being partially sclerified, helping the animal during the digging process. Unlike true moles, bellydruggers are social animals, living in reproductive couples: to recognize their partners, they use very low-frequency calls, since they are nearly blind.
Their olfactory is pretty developed for a bird, comparable to a kiwi, possessing also long sensorial barbs that cover the entire face of the animal. These important adaptations help bellydruggers to find food underground.
Eggs are usually incubated by males inside an enlarged tunnel, while females have the task of looking for food. After the hatch, both sexes switch their jobs several times before chicks become completely independent. This behavior is probably a reminiscence of their marine ancestors.
Bellydruggers prefer temperate climates, being present and well abundant across the entire Belgrano lowlands. They mostly prefer woodlands ecosystems, where the biomass of their common prey (like wormflies) is higher. Still, lots of populations can be found in suboptimal biomes, like Amery bay and some parts of the Scrubring.