Lima, Peru - Researchers believe that a 39 million-year-old whale fossil found in southern Peru may belong to the heaviest and largest animal ever recorded, according to a newly published study.

Scientists led by a group from the University of Pisa in Italy found the remains of the cetacean, named Perucetus colossus, in the Ica Desert along the southern coast of Peru.

The partial fossil uncovered includes 13 vertebrae, four ribs, and one hip bone - showing that the ancient species of whale still had small hind legs.

"Although the Perucetus' skeleton is not complete, rigorous estimates... indicate that the mass of the skeleton of Perucetus was about 5–8 tonnes [about 5.5-8.8 tons] - at least twice the skeletal mass of the largest living animal, the blue whale," lead researcher Giovanni Bianucci said.

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"The very heavy skeleton of Perucetus - which in life would have reached 20 meters [around 66 feet] in total body length - suggests that the body mass of this ancient cetacean may have been as much as 340 tonnes [about 375 tons], almost twice that of the largest blue whales and more than three times that estimated for Argentinosaurus, one of the largest dinosaurs ever found."

Scientists believe that whale displays "the highest degree of bone mass increase known to date, an adaptation associated with shallow diving," the study published in Nature on Wednesday said.

According to Bonucci, the whale's enormous body mass "indicates that cetaceans developed phenomena of gigantism at least twice: in relatively recent times, with the evolution of the large baleen whales that inhabit the modern oceans, and some 40 million years ago, with the radiation of the basilosaurids of which Perucetus is the most extraordinary representative."

Ph.D. student Marco Merella said the excavation of the giant whale was very challenging due to the size of the animal and its parts.

"Each of the vertebrae of Perucetus is so heavy - the lightest weighs over 100 kilograms [200 pounds]," Merella said. "In addition to making the excavation and preparation phases more difficult, heaviness greatly complicated the osteoanatomical analysis of the skeleton."