It had been defined as the heaviest animal ever to have lived on Earth, but the ancient cetacean Perucetus colossus which lived 39 million years ago probably weighed as much as a modern whale: a study published in Peer J by paleontologists from University of California-Davis and the Smithsonian Institution, who revised downwards the estimates published last August in Nature by a team of scholars led by paleontologist Giovanni Bianucci of the University of Pisa.
Both studies are based on the analysis of fossil bones recovered in Peru in the current Ica desert (which at the time of Perucetus was a sea), namely 13 vertebrae, 4 ribs and part of the pelvis.
According to the calculations of Bianucci's group, the skeletal mass of the animal weighed approximately 5-8 tons: from this data it was deduced that the cetacean (which in life would have reached 20 meters in length) could reach 340 tons of body mass , almost double the largest living animal, the blue whale (which reaches 30 meters in length).
According to paleobiologist Ryosuke Motani of the University of California, under these conditions Perucetus would have struggled to remain on the surface or even to leave the seabed.
“Doing anything in the water would have required continually swimming against gravity,” the expert points out.
Thus, together with Nick Pyenson of the Smithsonian Institute, he conducted a study that questions the assumptions on which the old estimates were based and, on the contrary, claims that a 20 meter long Perucetus could have weighed just over 110 tons, therefore much less of the 270 tons of the largest blue whales.
“The new weight allows the cetacean to come to the surface to breathe and recover from a dive like most whales do,” says Motani.
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