A hunter in the 24 hour darkness
Puijila darwini lived about 24 to 20 million years ago. During this time period, the landmass that is now the Arctic was located approximately where it is today. As such, Puijila darwini had to hunt both on land and in the ocean half the year in darkness, and through months of 24-hour complete darkness.
To adapt to this extremely difficult condition, Puijila darwini evolved with huge eyes in order to see its prey. It also developed long whiskers so that it could feel for fish in the darkness of deep and murky waters.
A land mammal ready for the sea
As both a land and sea mammal, Puijila darwini had to survive in two very different environments. It had to be a fast swimmer in the water and a fast runner on land.
To do this, it had webbed feet with five fully formed fingers and toes. This allowed it to not only swim in the ocean but also to run on land to potentially catch prey and evade predators. It most likely had fur similar to the modern day seal, which acted as an effective insulator in cold waters.
A fierce hunter
Puijila darwini was most likely a hunter on land and in water. To do this, its body was shaped to go through the water with minimum resistance while still being agile enough on land to hunt.
Besides having webbed feet with five fingers and toes to help it hunt on land and sea, it also had a very strong jaw-bone structure able to crunch through its prey. It also had a series of sharp teeth to catch and eat its prey.