Excerpt from the book Animals Evolution Avoided. This book describes 40 animals that ought to exist but don’t, because I made them up.
The Dosseroo was an Australian marsupial that became extinct in the 1970s after a series of bushfires in the Australian outback killed them all in one short week. The animals were unable to outrun the fires, either through laziness, a basic lack of fitness, or an inability to motivate themselves to preserve their existence.
The dosseroo was the marsupial equivalent of the cuckoo. A dosseroo was the exact same size as a kangaroo joey. A typical dosseroo would wait until a joey was out of his mother’s pouch and then quickly take the joey’s place. This was the only time in the dosseroo’s life when it would move at all quickly. The dosseroo would curl up inside the pouch and fall asleep for up to 24 hours at a time. All this time, the mother kangaroo would keep the dosseroo warm with her body heat.
The problems would usually start when the joey came back and tried to enter the pouch. Some mothers would shoo the joey away as they’d feel the dosseroo in the pouch and assume it was their baby. Other mother kangaroos would recognise the joey and try elaborate methods to extricate the dosseroo, even occasionally insisting that a male kangaroo kick their pouch very gently to make the dosseroo leave.
After the 24-hour period was over, the dosseroo would usually leave the pouch to eat some vegetation before lying down on the ground to wait for another joey to leave a mother’s pouch.
Dosseroos were believed to be modest creatures and would only try and mate if a male and female dosseroo accidentally climbed into a pouch at the same time. Any young dosseroos would inevitably be brought up in a large number of different pouches, which is why it’s believed these marsupials lost their sense of belonging and identity over the generations. This added to the natural ennui of these marsupials and affected their collective will to live. When the bush fires came, the dosseroos had no inclination to escape and were consumed en masse by the flames.