For countless centuries, the seas have been home to predators that made the mightiest hunters on land seem small by comparison. In the 2010s, scientists in Peru just might have found the greatest leviathan of them all. In 2023, they revealed it to the world. How might their discovery compare to other bygone giants like the megalodon, Mosasaurus, and modern apex predators like the orca? Was a sea creature to finally rival the colossal Blue Whale at last discovered? And what might the oceans be like if this ancient titan appeared in the modern day? Some reporting on this species has been all over the place with confusing, clickbait headlines and quote mined statements. Time to set the record straight on what just might be one of the largest predators of all time…
Name: Perucetus Colossus ("Colossal Whale from Peru")
Family: Basilosauridae (Early whales)
Time: 39-37 million years ago
Habitat: Shallow coastal seas
Length: 17-20 meters (56-66 feet)
Weight: 75-375(?) tons*
Diet: Almost certainly carnivore, unknown prey
*Read further on
This diagram demonstrates what bones were recovered and studied for the skeleton, with the white portions showing the unknown parts. As you can see, the whole skeleton was not found and certain parts like the head and upper body are still missing. These portions in gray were filled in with close relatives.
The research teams in Peru are working tirelessly to find, clean, and present more material; so this just offers the best image we have of this literal colossal titan so far.
With new material, comes the chance for new surprises. What can be presented right now is the fruit of dozens of persons' labor with what they have, so far, to present the most likely image of this bygone beast. More finds in the future undoubtedly will yield some surprises.
So what do we know so far? Quite a lot thankfully, both from the remains recovered as well as those of comparable animals. An ancient lineage that gave rise to some of the first large apex predators to take to the seas after the cataclysm which killed off the mosasaurs and other Mesozoic sea monsters.
Art by Julio Lacerda
#1: THE FIRST NEW GIANTS
The basilosaurs like Dorudon and Perucetus were some of the very first whales to truly start achieving massive sizes. It is this group Perucetus is thought to be a very unique member of. Sometimes considered the mammal versions of the mosasaur body plan, the basilosaurs ("Regal Reptiles", the fossils were mistaken for a sea serpent in the 1800s) were apex predators of their day. They also were some of the first whales that a modern observer could look at and immediately identify as a whale, even if they didn’t look quite like modern species. Some of the more ancestral traits were still visible, such as the nostrils only being about halfway up the snout. This is an in-between the earlier whales having their nose at the tip of the snout like most animals and the forehead-mounted blowhole in most modern whales.
Comparison of Artiocetus (sea-lion like whale forerunner), Dorudon (basilosaurid),
and a modern River Dolphin; showing how the nostrils changed position overtime
Many of this family also had vestigial hind limbs, which was also one of the bones found on Perucetus. Remnants that tell a story of small land animals on land venturing into the sea to become the mightiest mammals to ever exist.
This group was largely shallow water dwelling, not having the same adaptations we see in deep diving and filter feeding whales of today. Tail flukes were present but were likely smaller, meaning these whales were likely not as agile or fast as their modern counterparts. There also doesn’t appear to be a melon, an organ used to focus sound waves for sonar in most toothed whales today, like dolphins. These were predators that were mostly vision oriented. And formidable predators at that.
A basilosaur (Saghacetus) skull with the family's iconic teeth, photographed by Emőke Dénes
Unlike modern whales, which if they have teeth are largely the same size and conical shape throughout the mouth; these bygone beasts still had the multiple types of teeth of their terrestrial ancestors. This meant sharp, conical, recurved stabbing teeth upfront like a multiple canine fangs; and serrated, multi-pronged slicing teeth in the back that would’ve worked like a hacksaw whilst also potentially helping to filter out large quantities of fish, squid, and mollusks from the sea water they sucked up.
In other words, they ate just about anything.
#2: SIZE DOES MATTER
Ever since just the first few bones got pulled out of the ground to be admired and inspected in full, it quickly became very obvious that this animal was simply gargantuan. The sections found included several ribs and much of the middle portion of the spine, giving a good idea as to the length of Perucetus compared to its relatives; but leaving some traits like girth and mass debatable.
Some of the singular vertebrae were the largest pieces of backbone ever recovered for any animal known and set a new record! Very few except the absolute largest blue whales and the biggest of the big sauropods got even close. Compare Perucetus to some other famous giant predators to get an idea of how this whale truly was in a whole different league!
Top to Bottom: Mosasaurus, Perucetus, and Pliosaurus. All maximum probable size. Silhouettes adapted from their respective original artists
That said however…
#3: YOUR SIZE MAY VARY
You've no doubt heard the news articles proclaiming this giant to exceed 300 tons? The truth is a bit more complicated. The basilosaur family, whilst consistent in a lot of elements, did vary a lot in terms of bulk and shape. This means using them to reconstruct the missing body parts for Perucetus could result in very different predictions for how much it weighed.
Some of the group, like the namesake of the family, Basilosaurus itself, could reach staggering lengths of 15-20 meters, whilst having a thinner and more serpentine body and a much lighter weight than a modern whale of the same length. Others like Durodon had a more compact and bulky form that more closely resembled modern dolphins.
Going back to the Peruvian colossus, these different body types make it difficult to get an exact bearing on how much mass it had. Length estimates tend to be pretty consistent, between 17 and 20 meters, but how much tissue fits around this length is why the estimates seem all over the place. The ratio of weight from bone to blubber would be different and at times difficult to pin down.
Some of the lightest estimates have in the upper 70s tons for weight, whereas some of the heaviest are in excess of 370 tons! Don't buy the clickbait, that last number is almost certainly not true. Contrary to some news article headlines, it is extremely unlikely it was over 300 tons. That metric was considered implausible by the discoverers and researchers, and was only used to explore the potential upper limits to reconstruction. Let’s also remember we are only working off a single specimen, which might have been small, big, or average for its species. Not every blue whale is lucky enough to become a 200+ ton real-life kaiju after all! For now, the safest answer is to say that Perucetus potentially was in the same weight class as the blue whale and certainly would be within the top ranks of the largest animals known to have ever existed. Whether it was bigger or not is uncertain as it probably didn't best the record. Whether that means it was averaging over 100 tons or was smaller than that can’t be said. More fossils will be needed to clarify what the rest of the body looks like exactly and how the animal is built. Tentative as it is however, this does mean Perucetus was the largest of its family and drastically outsized the likes of other famous marine predators like Mosasaurus, Basilosaurus, and likely all but the absolute biggest Otodus megalodon.
Top to Bottom: Otodus megalodon (max size), Otodus megalodon (average size), Perucetus, Great White Shark ("Deep Blue"), Great White Shark (average female), Dunkleosteus Silhouettes adapted from their respective original artists
#4: BIG BONED BIOLOGY
Whether it truly was somewhat larger, somewhat smaller, or the same size as the modern blue whale, Perucetus already broke one record. It has the heaviest skeleton of any mammal, likely animals known thus far. The individual vertebrae were the heaviest of any backbones ever discovered.
The bones of this behemoth outweighed every other giant backbone known, both from other whales and from giant sauropod dinosaurs. Several backbones were nearly three times heavier than the same bones from a blue whale! Now that doesn't necessarily mean the rest of the animal is several times heavier, something a lot of news sites got wrong. Skeletons only make up a pretty small amount of the body mass and other tissue like muscle and blubber factors a lot more.
But the fact that the bones were so extremely dense and heavy implies a few things about the life of the animal. These aren't the bones you would find in a deep diving predator. These bones would act like ballast on a submarine, seen in shallow water dwelling animals that spend a lot of time near the bottom. It allows an animal to more efficiently move near the bottom of shallow shores without having to constantly spend energy swimming downwards.
This would imply that Perucetus was either dining on something near the bottom, or it was using these dense bones to sink down and weather choppy current more efficiently; maybe both. A very dense, big animal like this could dive in the shallows more easily and resist violent waves easily, similar to some large freighter ships.
#5: WHAT DOES A COLOSSUS EAT?
One of the missing parts to Perucetus’ body was the head. Best-guess reconstructions have to rely on the closest relatives, which were likely still quite similar. A jack of all trades dentition, that might have been one of the key reasons for early whales' success even in the face of rising competitors like other marine mammals and mega tooth sharks.
That said however, considering the sheer size difference between Perucetus and the next largest of its family, it's not impossible it might have had a much larger or differently shaped head than some current reconstructions. Most of the current reconstructions use the relatively small head to body size seen in animals like Basilosaurus. It's quite possible when the head is uncovered, that it might look very different from its relatives. Speculation about its current diet could be wrong, but if that happens it only means we got even more awesome finds to look at!
Current guesses about the diet have it at anything from mass suction feeding sea bottom animals like a living vacuum cleaner, or it might have been attacking prey and hunted other large animals. Perhaps both.
"Hope" the Blue Whale skeleton showing a huge, toothless mouth which bears baleen in life British Museum of Natural History
One thing that is almost certain, is that it wasn’t a long-jawed filter feeder like a majority of the largest whales alive today. These species, like the humpback, right, and gigantic blue whale; filter massive amounts of seawater to strain out millions of calories worth of plankton, fish, and krill. This is done with keratinous plates of hairy stands, called baleen. Baleen however is an extremely specialized trait that only started showing up in the whale family long after the Basilosaur group's time.
The early forebears of the baleen whale group, the Mysticeti, didn't start out with baleen either. Early members of that family also had a pretty generalized tooth structure not that different from their basilosaur cousins. Coronodon was such an ancestor of baleen whales, and it almost certainly had a very generalized diet of praying on large fish and other marine mammals, whilst also using its teeth to sift through sea water like some seals do today.
Coronodon skeletal by Robert W. Boessenecker, Brian L. Beatty & Jonathan H. Geisler
It’s not impossible plankton filter feeding evolved multiple times, it has in nature. There’s just no evidence that it ever appeared in the Basilosaur family. Any dedicated filter or sifting method defeating would require some pretty unique headgear.
The diet and ultimate appearance of the face for potentially one of the largest animals to ever exist is still largely unknown. It might have been gorging itself on enormous quantities of bottom dwelling creatures, it might have been preying upon other large marine animals and their carcasses; or it might have been a generalist jack of all trades and partook in a huge variety of to reach such enormous size.
#6: LEFTOVER LEGS?
Even today whales still do have leftover remnants of their ancestors' time on land. If you ever go to a museum, one of the more apparent ones is that whales still have a pelvis as a vestigial set of bone in the hip. Once in a while, due to a genetic throwback activating an ancestral trait, whales and dolphins have been found with hind limbs not that different from ancient whales.
A dolphin found with hind limbs due to a random genetic mutation
Most whales at the time of Perucetus still had legs. In fact one of the parts of the body besides the backbone and ribs discovered was the giant's pelvis. Now it certainly couldn't walk on land, these legs were just remnants left over from an earlier stage in the whale evolutionary family.
When the family that would become the whales first went to sea, they started out as amphibious and mostly propelled themselves with their feet. Some modern mammals like polar bears and sea lions do something similar. The difference here was the whale ancestor had and retained a fairly large tail that many primitive mammals in aftermath of the Mesozoic still had.
Ever notice a majority of hooves and predatory mammals today have very tiny or thin tails? It wasn't always that way. Most land mammals shrink their tails over time as a way of shedding weight and maintaining balance. In the seas with the ancestors of whales however, the tail over time took a bigger and bigger role with propulsion.
With the legs no longer being needed for propulsion, mutations that shrank them away wouldn't hinder the whales at all, and might even benefit it by reducing drag. This is a way how entire limbs might become vestigial in various animals.
In the generations that would follow the time of the basilosaurs, the tails and their flukes would only get bigger as the now mostly useless legs got smaller and smaller.
#7: WEIGHT IN - WHERE DOES IT STAND SWIM AMONGST GIANTS?
Assuming an averaged mass between 80-120 tons for Perucetus, this is how it measures up against some of the larger and well known giants of the sea. Note that for modern animals (marked with a *), size estimates are based on pools of potentially hundreds of individuals studied so far; and some species can have gigantic ranges in size.
Blue Whale* - Largest animal on record 100-210 tons
Perucetus colossus - Largest toothed whale on record 80-120+ tons
Fin Whale & Pacific Right Whale* - 2nd largest modern whales 60-120 tons
Otodus megalodon - Largest shark and fish on record 50-100 tons
Shastasaurus pacificus - Largest known marine reptile 50-80 tons
Sperm Whale* - Largest toothed predator of modern times 50-80 tons
Livyatan melvillei - Largest macro-predatory whale verified 45-70 tons
Pliosaurus rossicus - Largest confirmed plesiosaur 18-21 tons
Mosasaurus hoffmani - Largest known lizard and mosasaur 12-20 tons
Orca* - Largest known dolphin, current oceanic apex predator 7-11 tons
Fossil animals are often only known from a few or single specimens. In all likelihood given all animals have variable sizes between individuals and how rare it would be for a max sized individual to fossilize, larger specimens of the extinct species likely existed and are currently unknown.
As you can see, Perucetus certainly was enormous. And, if we go off what is likely, it could have been a contender to approach the same range as some blue whales. What is it as big as the record specimens? Probably not, but more specimens might change this.
Top to Bottom: Blue Whale (maximum size), Blue Whale (average size), Perucetus,
Orca bull (maximum size), Orca bull (average size) Silhouettes adapted from their respective original artists
#8: WHAT IF IT LIVED TODAY?
The shallow seas Perucetus roamed do still largely exist today. On the onset of climatic changes some 35-30 million years ago, the coasts of the world changed dramatically and what used to be shallow water became deep sea. This is likely what spelled the doom of the basilosaurs, as they were less adept in deep water than their more derived cousins which gave rise to modern whales. In the aftermath of the last ice age, numerous areas that were once coastline or dry land are now underwater; meaning habitats that might be suitable for Perucetus do exist.
Assuming no major environmental degradation and proper protections, it is quite possible the colossus of the seas might find suitable habitat. It would undoubtedly be the largest animal in the shallow seas and be a sight to behold from both the shoreline and near-shore ships humans frequent.
Food would be the major concern for the species, as humans have taxed the oceans greatly in the last few centuries. Considering it is unknown exactly what the colossal whale ate however, this is hard to pin down. The climate of the world roughly 40 million years ago was hotter than it is today, meaning the ocean climates Perucetus might be most comfortable in would be the equator and shallow gulfs, such as the Gulf of Mexico, Caribbean Sea, and archipelagos like Indonesia. It is extremely unlikely you’d see this giant roaming the distant, cold oceans around the north and south pole like the largest of modern whales.
#9: COULD ANYTHING HUNT IT?
Aside from humanity using large ships and harpoons, there are only two animals in the ocean known to kill and prey on whales weighing in the dozen to dozens of ton range. The Great White Shark and the Orca.
Great white sharks have been observed dispatching baleen whales several times larger than themselves when the opportunity arises. However, these are extremely rare instances, and typically involve whales up to or below 10 meters (~33 feet) long often being caught and entangled in rope for fishing equipment first. This means the whales were already exhausted and weakened before being targeted. The orca is a different story as the most powerful dolphin to ever exist, they are also indisputably the apex predators of the modern ocean. Multiple “types” or “cultures” orca exist, and each of them tend to have different diets and social habits. The type of orca most likely to try and attack a Perucetus in the tropical range the giant would dwell in would be the “Atlantic Type 2”. These orca are specialists at dispatching large marine mammals, often other dolphins and whales. They also do venture into potential modern habitat for Perucetus. Orca pods vary in numbers, led by a matriarch with the alpha bull being her eldest son as her chief lieutenant. Hunting parties can involve well over a dozen whales. Some of the polar orca have even bigger pods for hunting big game, but these whales would be unlikely to meet a tropic, shallow water Perucetus in this scenario.
A Match across a Sea of Time!
A Type 2 orca pod of six, led by a matriarch and lieutenant of near record size, against a near max size Perucetus
When these orca attack, pods can hit fast, and they can hit constantly for hours at a time. Even with great physical might and the potential for injury with smacks of the tail or ramming, whales hunted by orca pods almost exclusively managed to survive by outpacing or getting away from the pod. A coordinated pod attack is not something they can easily win. Even adult (though not max size) blue whales, whilst very rare prey, have been known to be killed by orca pods of sufficient size and persistence!
Orca skull diagram by Port Townsend Marine Science Center
Orca jaws are potentially the most powerful of any toothed predator in the modern age, with a maximum biting force unknown. These dolphins however can bite hard given they’ve been known to chomp through dense whale bone and crush smaller prey to a pulp. When attacking whales, wounds are typically done by tearing off chumps of the flippers; or slashing long length of hide to flay it in a maneuver called raking.
So could a pod of orca kill a Perucetus? Perhaps yes.
Perucetus would not have been as fast as modern whales and would have no chance of outpacing the orca. It would have to fight back. The orca would be much more agile and undoubtedly land dozens of hits before a retaliation could even be struck. The key difference however is that whereas large whales today largely rely on sheer size for defense and offense, Perucetus still would have had a formidable set of jaws of its own. Even with the exact specifics unknown, its dentition would’ve been broadly similar to its relatives. Meaning with sheer size of the teeth, the bite forces involved, and potential shredding surfaces on the back teeth; a bite from the Peruvian Colossus could quickly wind up being lethal to an orca. And with how many orca in a pod are bound to be needed to even have the chance of felling a whale this big, the Perucetus only needs a brief moment for one of the dolphins to underestimate an opponent it hadn’t faced before. A serious bite is going to quickly likely wind up being a badly bleeding or dead orca even as its body shred and rend the giant colossus.
The rest of the pod, if they ignored this and kept attacking, might have a good chance of killing the giant, nonetheless. But having one or several of their pod mates mauled; it is likely they would break off and seek easier prey. It's not like the Perucetus would even be much of a threat to them given the orca would prefer deeper waters and could easily outpace the earlier whale if it attempted to act aggressive for any reason. Incidents of orca pods harassing or killing Perucetus, or adult Perucetus likewise killing orca, would probably result from pods targeting young calves of the latter. It would be a rare event but not one that would be without notice.
#10: WHAT OF WHEN MAN MEETS WHALE?
Art by Joschua Knuppe
If the Peruvian Colossus of the whale existed in our oceans today, how would it react to humans? Any sufficiently large animal could certainly kill someone, and this would be no exception, but this would likely be an extremely rare event. Although Perucetus would chiefly live in shallow waters and be closer to human habitation, we are so different from any potential prey it might’ve had in the past that it likely wouldn’t know much of what to make of us. Incidents both ways could certainly happen. Perucetus, if it preyed on other marine mammals to any degree, might not know what to make of a small ship or boat and attack thinking it was food. Likewise, even if they were slower than modern whales, they would very easily outpace a swimmer and be more than large enough to consume them.
That said, considering its sheer size and propensity for living in the shallows, it would be very easy to spot it coming from a good distance away. Humans also look, taste, and sound so different from anything Perucetus might have encountered back in its time that it’s also quite probable it wouldn’t be very aggressive. It might be completely aloof towards humans and ignore them entirely, or potentially not see us on the menu at all and even show signs of gentle curiosity.
Biologist, Patrick Aryee, free diving with a sperm whale. Unless provoked, these giants are known to be docile
Something similar even happens today. Sperm Whales typically are calm and docile around humans. At times, even showing curiosity. Even with less intelligence and sociability, it’s not impossible a calm Perucetus might be the same way.
Sperm whales had been known to attack boats in the past, but this was a learned behavior because this was during the height of whaling. In 1851, a whaling ship, the Ann Alexander attempted to hunt a large bull sperm whale. After being harpooned, the whale fought back. After destroying several smaller boats, it rammed and sunk the main ship. When the sailors managed to return and reported the incident, word reached the ear of Moby Dick's author Herman Melville. Life imitating fiction with his story of a ship-sinking leviathan, he wrote back-
‘It is really & truly a surprising coincidence – to say the least. I make no doubt it is Moby Dick himself!… Ye Gods! What a Commentator is this Ann Alexander whale…
I wonder if my evil art has raised this monster!'
Unlike in fiction, animals aren't monsters. It was attacked and given violence, and it gave it back. When heedless people cross paths with powerful animals, it can cause tragedy.
To witness such a sight as the colossus at sea, it truly might have been a magnificent sight! But, perhaps one best admired from afar for the sake of all parties involved...
Hope to see more of this mysterious colossus? Consider donating some spare money to this fund. The paleontologists in Peru have some magnificent finds to work on, and could use all the facilities or equipment they could get!