Researchers writing in Nature magazine say the fossil skeleton of a newly discovered carnivorous animal,
Puijila darwini, is a "missing link" in the evolution of the group that today includes seals, sea lions, and the walrus.
Modern seals, sea lions, and walruses all have flippers—limb adaptations for swimming in water. These adaptations evolved over time, as some terrestrial animals moved to a semi-aquatic lifestyle. Until now, the morphological evidence for this transition from land to water was weak.
Skeletal illustration of Puijila darwini. Credit: Mark A. Klingler/Carnegie Museum of Natural History