Learning from the heaviest ancient whale

A groundbreaking study published in Nature by Bianucci et al.has reported the discovery of a new basilosaurid species,Perucetus colossus(Figure 1).The incomplete fossil skeleton found in Peru is around 39 million years old.This ancient whale challenges the long-held belief that the blue whale represents the largest known animal to have ever lived on Earth.P.colossus is estimated to have had a body mass between 85 and 340 tons,with an average of 180 tons.1 In comparison,extant blue whales have an estimated body mass of 100–150 tons.The new study proposes that P.colossus was adapted to a fully aquatic lifestyle in shallow water with slow swimming speeds,similar to extant manatees.Elevated bone mass would have aided buoyancy control while diving to shallow depths,as seen in modern-day sirenians.This new discovery not only challenges our understanding of mammalian maximum body mass evolution,but it also expands our knowledge of the lifestyle of ancient cetaceans.