Unlike modern pinnipeds, it did not have flippers and its shape was otter-like, albeit more specialized; its skull and teeth are the features that most clearly indicate that it is a seal.

Phylogenetic studies including molecular evidence suggest a sister relationship between seals, bears and musteloids (weasels and otters).

It had been popularly assumed that land mammals at some point transitioned to being more marine, in essence "returning to the sea" in order to gain some sort of survival advantage.

In other words, Puijila is a transitional fossil that provides information about how the seals returned to the sea, similar to how Archaeopteryx illuminates the origin of birds.

This novel species was discovered in 2007 by Natalia Rybczynski and her team using surface collection and screening at an early Miocene lake deposit of the Haughton Formation of Devon Island, Nunavut, Canada.