The Perucetus colossusa recently discovered ancient species of whale, is considered one of the largest and heaviest animals ever recordedaccording to a study published in natures. Estimates of its size and weight, based on a partial skeleton, rival those of the blue whale, formerly considered the heaviest animal ever. These findings suggest that the trend towards gigantism in marine mammals may have started earlier than previously thought.
The fossil record of cetaceans, a suborder of mammals that includes dolphins, whales and porpoises is of great importance in documenting the evolutionary history of mammalian life when some land animals were returning to the ocean. Previous studies have identified adaptations to an aquatic lifestyle, including a tendency to gigantism and an associated increase in body mass, although maximal body mass was thought to be a relatively recent diversification.
Eli Amson and colleagues at the State Museum of Natural History in Stuttgart, Germany a new basilosaurid whale with an estimated skeletal mass greater than that of any known mammal or marine creature. Called P. colossus, the animal was modeled from a partial skeleton, consisting of 13 vertebrae, 4 ribs and 1 hip bone, discovered in southern Peru and estimated to be around 39 million years old. The skeletal mass is expected to be 2-3 times that of a 25m long blue whale; the authors estimated that P. colossus had a body mass of between 85 and 340 tons. Since the estimated body mass equals or exceeds that of the blue whale, this new species would challenge the blue whale’s status as the heaviest animal ever. These findings indicate that cetaceans reached maximum body mass about 30 million years earlier than previously thought, with P. colossus features fully adapted to an aquatic environment. The buoyancy associated with increased bone mass is consistent with a shallow-water lifestyle, supporting the theory that basilosaurids were hyperspecialized for this type of coastal environment and shedding further light on this ancient animal order.