Meet Palaeophis Colossaeus, the Largest Sea Snake of All Time

By: Desiree Bowie  | 
A white snake with black or brown stripes swimming through coral in blue water
Imagine this, the length of a bus, swimming toward you. No thank you. / Getty Images
Key Takeaways
  • Palaeophis colossaeus was a massive sea snake from the lower Eocene era, reaching lengths comparable to a school bus and ruling the ancient oceans.
  • This extinct species lived in the Tethys Sea region, which is now North Africa, and thrived in warm, shallow marine environments.
  • Fossil records indicate its length varied, with estimates ranging from 26.6 to 40.4 feet (8.1 to 12.3 meters), making it one of the largest sea snakes known.

Palaeophis colossaeus, a sea snake from the lower Eocene era, ruled the oceans millions of years ago as one of the largest of its kind. This period saw the emergence and diversification of early forms of many modern animal groups, including mammals, birds and marine species.

Rivaling a school bus in length, this ancient snake exemplifies the massive size and diversity that characterized prehistoric aquatic snakes during a time of significant evolutionary change.



Academic Research on Palaeophis

Some of what we've learned about Palaeophis colossaeus derives from a 2018 research paper by Jacob A. McCartney, Eric M. Roberts, Leif Tapanila and Maureen A. O’Leary.

Their findings provided crucial insights into the size, habitat and evolutionary characteristics of the aquatic snake, shedding light on its adaptation to ancient marine environments and its place in the ecological history of the Trans-Saharan region.


According to their research, the extinct genus Palaeophis was part of a group of prehistoric sea snakes from the Eocene epoch. Other species in this genus include Palaeophis maghrebianus, found in Morocco, and Palaeophis virginianus, identified in North America. While sharing general characteristics, these species had unique adaptations, reflecting the diversity within the genus.

Palaeophis colossaeus is believed to have been one of the larger species in the genus, potentially surpassing the size of its Moroccan relative, Palaeophis maghrebianus.

Distinguished by its robust and broad vertebrae, Palaeophis colossaeus shows clear skeletal distinctions compared to other species in the genus. It is thought to have had slightly narrower and more elongated bones.

Modern Counterparts: Pythons and Anacondas

In terms of size and aquatic lifestyle, the ancient sea snake's closest modern equivalents might be large marine pythons and anacondas.

Contemporary snakes — like the reticulated python and the green anaconda — share traits like substantial size and a semi-aquatic lifestyle with the Palaeophis genus. Anacondas, for instance, are among the heaviest and longest snakes today and are well-adapted to aquatic environments.

However, these modern snakes belong to different families and have evolved independently, exhibiting distinct differences from the ancient species.


Where Did the Ancient Aquatic Snake Live?

The extinct sea snake, believed to have inhabited the area now known as North Africa, lived during the Eocene epoch, a period that spanned from approximately 56 to 33.9 million years ago.

Fossil evidence of this giant sea snake has been found in areas that were part of the ancient Tethys Sea, which existed between the ancient supercontinents of Gondwana and Laurasia before the opening of the Indian and Atlantic Oceans.


During the Eocene, the Earth's climate was warmer, and sea levels were higher, creating extensive shallow marine environments ideal for marine life, including Palaeophis colossaeus. The Tethys Sea would have offered a rich and diverse ecosystem suitable for a large, predatory sea snake.

However, specific details about this giant serpent's exact habitat preferences and lifestyle are largely speculative, as our understanding is based solely on fossil records and the geological context of those findings.


How Big Was Palaeophis Colossaeus?

Fossil records suggest that Palaeophis colossaeus was the largest snake ever to exist in the ocean, but the fossils vary in length. According to the research paper mentioned earlier, some fossils place it at 40.4 feet (12.3 meters) in length, while others cap the snake at 26.6 feet (8.1 meters).

The differences in length estimates are due to variations in specimen sizes. This suggests that the species varied broadly in terms of length and weight.


But one thing is certain: You wouldn't want to encounter any Palaeophis species or its gigantic terrestrial counterpart, Titanoboa cerrejonensis from Colombia's Paleocene era, in the wild.

The mighty Titanoboa is believed to have measured around 42 feet (about 13 meters) in length and could have weighed as much as 2,500 pounds (1,135 kilograms). These measurements, inferred from their vertebrae, rank them among the largest snakes known in history.

Bony Adaptations

Palaeophis species are divided into "primitive" and "advanced" groups. "Advanced" Palaeophis have features like tall pterapophyses (bony projections on the vertebrae) and small prezygapophyses (articulating surfaces of the vertebrae), indicating better swimming adaptation.

Palaeophis colossaeus, however, is in the "primitive" group, lacking such specializations. Its broad vertebrae suggest a less streamlined body, but some features hint at aquatic adaptation. This species' exact swimming abilities and habitat are still under study.


Did Palaeophis Colossaeus Eat Whales?

Many claims surround the aquatic snake's massive appetite, particularly its affinity for ingesting whales. This hypothesis is based on several aspects of its existence and the different species in its environment.

One major factor in driving this claim is its formidable size. Being one of the largest known sea snakes implies a capability to hunt larger prey.


Then there's its home base. During the Eocene epoch, this snake shared its marine habitat with early forms of whales, which were generally smaller than its modern relatives and belonged to different species.

These early, smaller whale species could have been suitable prey for a large predator like Palaeophis colossaeus. Drawing parallels with modern large marine predators further supports the hypothesis that the aquatic predator might have included these smaller whale species in its diet.

For example, in modern oceans, large predators like great white sharks or orcas are known to hunt smaller marine mammals, including seals or even smaller whale species. So if larger marine predators often target sizable, nutritious prey that are smaller than themselves, it's possible that Palaeophis colossaeus did the same.


So what do we know about the feeding habits of this serpent?

Unfortunately, nothing concrete. The diet of the prehistoric giant sea snake is intriguing due to the absence of cranial fossils that would reveal the size of its mouth. Scientists explore this mystery by examining the skulls of related species.

Some have less kinetic skulls with elongated bones, suggesting a large gape for consuming big prey. Others, with more kinetic skulls, could eat even larger food.

However, the variety of these related species makes it difficult to draw definite conclusions about the sea snake's diet. Depending on the environment, its feeding habits could have ranged from fish and small crocodilians to turtles, mammals or small whales.

The snake's size would have deterred most predators, leaving only large dyrosaurids and sharks as potential threats.


Other Giant Sea Snakes

Palaeophis colossaeus is a prime example of the diversity and adaptability of sea snakes. Alongside this giant, several other species, both ancient and contemporary, highlight the evolutionary journey of marine reptiles:

  • Olive sea snake (Aipysurus laevis): Inhabiting the coral reefs of the Pacific and Indian Oceans, the olive sea snake is recognized for its unique olive-green coloration. Adapted to coral reef environments, it preys on fish and marine invertebrates. While generally nonaggressive, it can display aggression if disturbed.
  • Giant sea snake (Hydrophis spiralis): As the largest modern sea snake, it can reach up to 9.8 feet (3 meters) in length. Residing in the warm coastal waters of the Indo-Pacific, this venomous species predominantly feeds on small fish, including eels. Its formidable size and venom make it a top predator in its natural habitat.
  • Banded sea krait (Laticauda colubrina): Distinguished by its black and white bands, the banded sea krait has a unique amphibious lifestyle, living in the ocean and laying eggs on land. Although it possesses highly potent venom, it is typically not aggressive toward humans unless provoked.
  • Palaeophis toliapicus: This ancient sea snake from the Eocene era is known from marine deposits. It was a significant predator during its time, with adaptations for fully aquatic life in warm seas.
  • Pterosphenus schucherti: This Eocene sea snake, discovered in North America, was well-adapted for life in warm, shallow marine environments. Pterosphenus schucherti likely preyed on small fish and aquatic invertebrates, using its agility and stealth for hunting.

This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.


Frequently Asked Questions

How did Palaeophis colossaeus adapt to its marine environment?
Palaeophis colossaeus had a streamlined body and paddle-like limbs that allowed it to navigate the ancient seas efficiently. Its robust vertebrae provided structural support for its large size, aiding in swimming and capturing prey.
What did Palaeophis colossaeus primarily eat?
Palaeophis colossaeus likely preyed on large marine creatures such as fish, mollusks and possibly smaller marine reptiles, using its powerful jaws and sharp teeth to capture and consume its prey.