The heaviest animal ever to inhabit the Earth, with a body mass that could reach 340 tons: it is Perucetus colossus, a primitive cetacean that lived millions of years ago, discovered in Peru by a team of scholars led by paleontologists from the University of Pisa. The research, published yesterday in the journal Nature, began with findings 13 years ago of the fossil remains of the cetacean's bones, recovered in subsequent excavation campaigns. The fossil bones recovered in the present-day Ica Desert, which was a sea at the time of Perucetus, now preserved at the Museum of Natural History in Lima, consist of thirteen vertebrae, four ribs and part of the pelvis, the latter indicating that Perucetus still had small hind legs. "Rigorous estimates based on measurement of the preserved bones and comparison with a large database of present-day and fossil organisms," explained Professor Giovanni Bianucci of the University of Pisa, first author and coordinator of the research, "indicate that the skeletal mass of Perucetus was about 5 to 8 tons, which is at least double the skeletal mass of the largest living animal, the blue whale. The very heavy skeleton suggests how the cetacean, which in life would have reached 20 meters in length, could have reached 340 tons of body mass, "almost twice the size of the largest blue whale," Bianucci said, "and more than three times what was estimated for Argentinosaurus, one of the largest dinosaurs ever found. The discovery of Perucetus, in which other Italian geologists and paleontologists from the universities of Milano-Bicocca and Camerino also participated, joined by researchers from Peru and several European nationalities, promises to rewrite a chapter in cetacean history: "The enormous body mass of Perucetus," Bianucci pointed out, "indicates that cetaceans have been protagonists of gigantism phenomena in at least two phases: in relatively recent times, with the evolution of the large whales and fin whales that populate modern oceans, and about 40 million years ago".
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