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Scientific Classification
















Basilosaurus sp.


Basilosaurus isis as it appeared in the documentary Walking with Beasts in 2001

Basilosaurus, sometimes known by its scientific synonym Zeuglodon, is a genus of ancient cetaceans that lived during the late Eocene, they are thought to have died out 33 million years ago, this was during the time the Eocene epoch ended and the Oligocene started. These primitive marine mammals look nothing like today’s cetaceans. They were long and serpentine. Basilosaurus is often suggested as the explanation for sea serpent and lake monster reports. Basilosaurus was one of the largest animals of its time at 66 ft with some non peer reviewed sizes putting it at 70 ft. They are two species (other species from across the world have been assigned, but they turn out to be other Eocene cetaceans). The type species from North America, Basilosaurus cetoides is commonly found on the gulf coast of the Southern US (with a possible expectation) and Basilosaurus isis which is found throughout Northern Africa but the most complete skeletons of the species come from Egypt. Basilosaurus isis and the role it played in its environment is well understood. These fossils come from the Wadi El Hitan formation, the Wadi El Hitan is now considered a world heritage site, and is one of the most prized fossil locations in Egypt. Fossils from Wadi El Hitan show that B. isis was a predator attacking a smaller whale called durodon and many fish and possibly sharks. Basilosaurus cetoides more likely just fed on large sharks and fish. It should be noted that most prehistoric cetaceans are all found in the same areas.

Basilosaurus evolved from early cetaceans such as Pakicetus. Genetic tests show that whales are closely related to Hippos. The original idea of whale evolution was that whales evolved from mesonychids, a family of hoofed predators. While the current theory on whale evolution still places whales as ungulates, many scientists no longer support the original conclusion that cetaceans evolved from the mesonychid branch. Basilosaurus is contained in the cetacean parvorder Archeoceti, this is alongside the extant parvorders of Odontoceti (toothed whales) and Mysticeti (Baleen Whales). The idea of archeoceti was first proposed by Flower in 1883, this classification is often used but some scientists disagree and claim that Archeoceti should not be used. These scientists who oppose archeoceti believe that Odontoceti, Mysticeti and the extinct early cetaceans who are fully aquatic all belong in the taxonomic classification of Pelagiceti (first proposed by Uhen in 2008). Basilosaurus is still considered to be a cetacean.

Despite being classified as a cetacean, Basilosaurus has a name which describes it as a king lizard. This was due to the fact that the scientist who named Basilosaurus back in the 1830s (Harlan) noted Basilosaurus as looking quite a lot like the massive prehistoric reptiles (such as mosasaurids, plesiosaurs and dinosaurs). The name Zeuglodon was recommended later after a geological conference and a paper made by anatomist, paleontologist and biologist Richard Owen, but due to the fact that the original scientific describer is the only one who can rename a species, the name Basilosaurus was stuck (this is a rule in taxonomy). Harlan did agree to rename to Zeuglodon in a paper, but never got round to it. An interesting thing that was mentioned in Owen's redescription is the fact that he stated that Basilosaurus was probably a herbivore due to its teeth, something that is not true by the known data and evidence. Mainly the fact that paleontologists have found its stomach contents and the same teeth can be seen in all carnivorous mammal groups. Despite the name being sorted out as Basilosaurus, Zeuglodon is preferred by cryptozoologists. The name Zeuglodon was used a fair bit of the time or at least in pockets throughout its description history.

If these primitive whales are still alive, they would certainly fit with a few select characteristics of Basilosaurus, such as a long body. However, many sightings are based on outdated, overly serpentine designs from the 1950s. Any lake monsters and sea serpents present an elongated, serpentine shape, similar to Basilosaurus. In addition, many sea serpents and lake monsters have been reported from northern waters that are thought to be too cold for reptiles such as plesiosaurs or giant snakes, but these same waters would be fine for an aquatic mammal. While this could be the case Basilosaurus has no evidence it contained much blubber and in its time it did not need as much blubber as modern whales (although evolving it could be the case, but it's not the most likely option based on the serpentine accounts).

Sea serpents and lake monsters are also frequently described as having bits of hair (especially a mane). Hair is mainly a mammalian feature and is not present in any reptiles. The swimming style of Basilosaurus has been studied more in recent years. It had a vertical spine that would have been quite flexible in life. While some cryptzoologists note that features of hairy sea monsters may be evidence for a Basilosaurid whale, Basilosaurus is said to have lost most of its hair. It likely only had very scanty bits of hair. Whales as they got closer to modern times seemed to lose much more of their hair. "Hair" in some sea monsters (globsters) is attributed to decomposing whale tissue. Decomposing whales have been blamed for many sea monster sightings. The spine flexibility comes from the aforementioned outdated perceptions of Basilosaurus.

In recent years the animal has become the primary focus of several cryptozoology researchers who theorize that the animal may be responsible for some modern reports of Lake Monsters and Sea Serpents. The problem here is that the sightings only match now outdated concepts, for example sightings of the Con Rit are said to be of armour plated Basilosaurids. This likely comes from texts that explained that some fossils of archeocetes show a type of armour, this is now considered to be an error. Some cryptozoologists are still using the already unlikely and (as previously noted) outdated snake perceptions. While the last Basilosaurus fossils come from rock layers that are around 33.9 million years old, it is not a terrible concept to think it could have survived past that time and into modern times. Although this is most likely not the case as most skeptical minds and paleontologists agree, due to the fact that Basilosaurus went extinct during an extinction event that would not favor its survival. Basilosaurus was too specialized and it went extinct during the Eocene-Oligocene event which likely made food stocks very hard for the whale and environmental changes are not healthy for specialized creatures. There should be some fossil evidence of it surviving the event, given the fact that whale fossils are quite frequent, we even have whale fossils up in layers that are dated to be from very recent (even early Holocene) times.


Basilosaurus seems to be a better choice then the Plesiosaurus, Pliosaurus, Icthyosaurus or Mosasaurus due to the fact that it's more recent in the fossil record and has mammalian attributes, but the evidence seems to point to the fact that it's still most likely not the case. However it is a possibility, just not a very likely one. This is based on many details of its anatomy and our current understanding of its biology.


Sources you cannot find much of on the internet[]

1) A Review Of North American Basilosauridae.

Sources you can find on the internet[]