A Missing Link
A Freshwater Phase
Puijila is providing insight into the evolutionary history of characteristics in the land-to-sea transition, and that includes behavioural characteristics. For example, Puijila was found in a freshwater lake deposit. This fact suggests that in pinnipeds, the land-to-sea transition did not occur on the shores of an ocean, but rather, included a freshwater phase.
Charles Darwin foretold of an animal such as Puijila. While musing about pinnipeds in On the Origin of Species by Means of Natural Selection (1859), he predicted
"A strictly terrestrial animal, by occasionally hunting for food in shallow water, then in streams or lakes, might at last be converted into an animal so thoroughly aquatic as to brave the open ocean."
Needless to say, naming the animal Puijila darwini in his honour seemed appropriate.
Puijila may also offer clues on the role of the environment and geography in early pinniped evolution. For example, Puijila is the first fossil pinniped found in the High Arctic. Finding such a primitive fossil there may indicate that the Arctic region was a centre of dispersal for early pinnipeds. This contrasts with the prevailing hypothesis, which holds that pinnipeds originated on the Pacific coast of North America.