What is the oldest known penguin fossil genus?

Waimanu is the oldest known penguin fossil genus.

Waimanu fossils come from Paleocene rocks in New Zealand and date to about 60 million years ago, only a few million years after the mass extinction at the end of the Cretaceous Period. The name means “water bird” in Māori.

The fossils show that early penguins were already adapted for swimming, although Waimanu species retained more primitive body proportions than modern penguins. They lived long before the ice-covered Antarctic environments commonly associated with penguins today.

Waimanu is not the only fossil penguin genus. Later forms such as Palaeeudyptes and Anthropornis included very large species, but their fossils are younger than the earliest Waimanu material.