Ancient whale from Peru may be most massive animal ever on Earth
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[August 03, 2023]
By Will Dunham
(Reuters) - Move over, blue whale. There is a new contender for the most
massive animal in Earth's history.
Scientists on Wednesday described fossils of an early whale unearthed in
Peru called Perucetus colossus that lived about 38-40 million years ago
during the Eocene epoch - a creature built somewhat like a manatee that
may have topped the mass of the blue whale, long considered the heftiest
animal on record.
The researchers estimated that Perucetus (pronounced per-oo-SEE-tus) was
about 66 feet (20 meters) long and weighed up to 340 metric tons, a mass
that would exceed any other known animal including today's blue whale
and the largest dinosaurs. Its scientific name means "colossal Peruvian
whale."
"The main feature of this animal is certainly the extreme weight, which
suggests that evolution can generate organisms that have characteristics
that go beyond our imagination," said paleontologist Giovanni Bianucci
of the University of Pisa in Italy, lead author of the research
published in the journal Nature.
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The minimum mass estimate for Perucetus was 85 tons, with an average
estimate of 180 tons. The biggest-known blue whale weighed around 190
tons, though it was longer than Perucetus at 110 feet (33.5 meters).
Argentinosaurus, a long-necked, four-legged herbivore that lived about
95 million years ago in Argentina and was ranked in a study published in
May as the most-massive dinosaur, was estimated at about 76 tons.
The partial skeleton of Perucetus was excavated in a coastal desert of
southern Peru - a region rich with whale fossils - with 13 vertebrae,
four ribs and one hip bone. The bones, unusually voluminous, were
extremely dense and compact. This characteristic, called
pachyosteosclerosis, is absent in living cetaceans - the group including
whales, dolphins and porpoises - but present in sirenians, another
marine mammal group including manatees and dugongs.
Its skeletal mass alone was estimated at between 5 and 8 tons, at least
twice that of the blue whale.
"Its fat, bloated body may have been more like that of a sirenian than
of any living whale. Among sirenians, due to its giant size and probable
similar lifestyle, it could recall Steller's sea cow, discovered in 1741
and exterminated by humans a few years later," Bianucci said.
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![](../images/080323PIX/news_j21.jpg)
Perucetus colossus, an early whale from
Peru that lived about 38-40 million years ago, a marine mammal built
somewhat like a manatee that may have exceeded the mass of the blue
whale, long considered the heftiest animal on record, is seen in an
undated artist's rendition. Also pictured are a sawfish and another
early whale, Supayacetus. Alberto Gennari/Handout via REUTERS
![](http://archives.lincolndailynews.com/2019/Sep/05/images/ads/current/stclara_lda_SPONSOR_090519.png)
No cranial or tooth remains were found, making interpretation of its
diet and lifestyle tougher. The researchers suspect Perucetus lived
like sirenians - not an active predator but an animal that fed near
the bottom of shallow coastal waters.
"Because of its heavy skeleton and, most likely, its very voluminous
body, this animal was certainly a slow swimmer. This appears to me,
at this stage of our knowledge, as a kind of peaceful giant, a bit
like a super-sized manatee. It must have been a very impressive
animal, but maybe not so scary," said paleontologist Olivier Lambert
of the Royal Belgian Institute of Natural Sciences in Brussels.
"Perhaps it was herbivorous like the sirenians, but this would be
the only case among cetaceans. Perhaps it fed on small mollusks and
crustaceans in sandy bottoms like the extant gray whale. Or it could
have been a scavenger on vertebrate carcasses, similar to some
extant large-body sharks," Bianucci said.
The researchers said it was unlikely Perucetus was a filter-feeder
like today's baleen whales including the blue whale.
Whales evolved a bit more than 50 million years ago from hoofed,
land-dwelling mammals as big as a medium-sized dog. Perucetus still
possessed vestigial back limbs.
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Skeletal traits indicate Perucetus was related to Basilosaurus,
another early whale that was similar in length but less massive.
Basilosaurus, however, was an active predator boasting a streamlined
body, powerful jaws and large teeth.
"Perucetus indicates that cetaceans developed gigantism at least
twice: in relatively recent times, with the evolution of the large
baleen whales, and some 40 million years ago, with the radiation of
the Basilosaurus relatives of which Perucetus is the most
extraordinary representative," Bianucci said.
(Reporting by Will Dunham in Washington, Editing by Rosalba O'Brien)
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