Fossil of modern whales' ancient relative discovered in Peru

Scientists have gained a new insight into the evolution of baleen whales after the discovery of fossil remains from 36 million years ago at Playa Media Luna in Peru.

It was already known that baleen whales, such as blue and humpback whales, shared a common ancestor with toothed whales, which used teeth to grab its prey. The latest discovery appears to be the earliest relative of baleen whales after the branches split in two. The whale, named Mystacodon selensis, was around four metres in length and still had teeth. However, analysis of its skill, jaw and teeth indicates it fed by straining its prey before expelling the water, similar to how baleen whales feed.

One unexpected discovery from this latest fossil find is that it appears to have still had small limbs sticking out from its body. It had previously been thought that both branches of the family tree had lost their limbs during evolution before splitting.

Full report:
Earliest Mysticete from the Late Eocene of Peru Sheds New Light on the Origin of Baleen Whales
Manuel Martínez-Cáceres, Giovanni Bianucci, Claudio Di Celma, Rodolfo Salas-Gismondi, Etienne Steurbaut, Mario Urbina, Christian de Muizon
Current Biology