While flightless in the air, penguins "fly" through water with ease thanks to a variety of adaptations – many of which are actually in their brains. By studying 34-million-year-old penguin skulls, researchers hope to better understand the changes in their brain anatomy and sensory abilities that accompanied this transition to water. The findings were published in the Journal of Vertebrate Paleontology this week. 

These charismatic birds have more than 60 million years of history, and there’s still a lot we don’t know about penguin brain evolution. To investigate the changes that occurred in their brains (and when they occurred), an international team led by Claudia Tambussi of CONICET used CT scans to create virtual endocasts (or internal casts) of three skulls belonging to three ancient penguin species collected from the Eocene La Meseta Formation of Seymour Island in Antarctica. They also compared these with data from multiple extinct and living penguin species, as well as other birds. 

"Penguins are considered flightless, but when it comes to wing-propelled diving they are essentially practicing underwater flight," study co-author Daniel Ksepka of North Carolina State University said in a statement. "The brain morphology reflects this as penguins retain an overall ‘flight-ready’ brain."

They found that an area called the Wulst (which is linked to complex visual functions) was enlarged – suggesting an increase in visual complexity – but olfaction was reduced. Additionally, the ear region revealed that the position of their heads helped penguins maintain equilibrium. "The neuroanatomy of penguins was still evolving roughly 30 million years after the loss of aerial flight," added Ksepka, "with trends such as the expansion of the Wulst and reduction of the olfactory bulbs still in progress." 

Early penguins had many of the adaptations we see in modern penguins, as well as adaptations found in modern flying birds – which attests to their unique way of swimming.

^{On Seymour Island emerges the La Meseta Formation, the most prolific locality for fossil penguin remains worldwide in terms of raw abundance. Journal of Vertebrate Paleontology}