Kaikaifilu

## KaikaifiluKaykay Snake

* **Skull Length** of 1.2 meters (4 feet)
* **Top Speed** of 27 kilometers (17 miles) per hour
* **Acceleration** of 7.5 meters (25 feet) per second
* Possesses heterodont dentition

***“ A deadly hunter. Kaikaifilu. ”***

― **David Attenborough**, *Coasts*
***Kaikaifilu*** (named after "Kaykayfilu", which translates to "Kaykay [the] Snake", a serpent god in Mapuche mythology that serves as the supreme ruler of the seas and all its inhabitants) is a genus of mosasaur that lived in the López de Bertodano Formation, Seymour Island, Antarctica, 66 million years ago, during the Maastrichtian stage of the Late Cretaceous Period.

## Paleobiology

### Size and Physique

*Kaikaifilu* known mainly from preserved parts of its skull, which, based on the skull of the tylosaurine *Taniwhasaurus*, may have reached a length of 1.2 meters (4 feet), possessing heterodont dentition (differently-shaped teeth), a feature not seen in any other mosasaur except *Eremiasaurus* of the Ouled Abdoun Basin in Morocco. According to the calculations of Dr. Gregory S. Paul, *Kaikaifilu* is estimated to reach a size of 10 meters (33 feet) and a weight of three metric tons (3.3 short tons).

It is unknown whether *Kaikaifilu* is a mosasaurine or a tylosaurine due to having features that contradict with its classification as a tylosaurine. Prehistoric Planet appears to depict *Kaikaifilu* as a tylosaurine due to being proportionally slimmer than *Mosasaurus*. Regardless, it is medium-sized by mosasaur standards, being only around two-thirds the size of the largest mosasaurs. However, following *Mosasaurus* and *Moanasaurus* (both of which also live in the same formation as *Kaikaifilu*), it is the third-largest mosasaur of the Southern Hemisphere, and thus one of the largest marine predators to ever live in the waters around Antarctica.

### Prehistoric Planet's Depiction

Prehistoric Planet depicts *Kaikaifilu* as being countershaded like its relative *Mosasaurus*. While mostly black, its underbelly, the edges of its flippers and tail fin, and five bands wrapping around the center of its tail are creamy white. Since it is not as big as its famous relative, *Kaikaifilu*, though a dangerous hunter in its own right, is not as feared, given how a pod of *Tuarangisaurus* were willing to fight it off, but not the significantly larger and more powerful *Mosasaurus* in Oceans.

## Paleoecology

### Paleoenvironment

*Main: López de Bertodano Formation, Tahora Formation*

Main: López de Bertodano Formation, Tahora Formation

***“ Back in the shallow waters of Zealandia, large groups of Tuarangisaurs have come together. They propel themselves with all four fins, and travel almost effortlessly to find the fish shoals that gather here in summer. ”***

― **David Attenborough**, *Coasts*
*Kaikaifilu* lived 66 million years ago in the López de Bertodano Formation of Seymour Island, which showed that the waters surrounding Antarctica were warmer than they are in the modern day, though, at 4 - 12 degrees Celsius (39.2 - 54 degrees Fahrenheit), the area was still very much cold, hence, the seas of Antarctica would have still been plausibly covered in sheets of ice, just as depicted in the sixth segment of Oceans. While there is no evidence of *Kaikaifilu* living in the warmer waters of the Tahora Formation, given the distance between it and Antarctica, its presence in the warmer seas covering the submerged continent of Zealandia is not entirely implausible, an idea supported by the fact that its slightly larger relative, the *Prognathodon*-sized *Moanasaurus*, was present in both the Tahora and López de Bertodano Formation (based off of isolated teeth).

### Hunting Tactics and Feeding Preferences

As believed to be the case for mosasaurs, this marine reptile likely lead a solitary life. As a predator, it always goes for what appears to be the weakest and easiest of prey, like a pregnant *Tuarangisaurus*. Even so, predators are not irrationally persistent in their pursuit of prey, they would back off when the risk and degree of injury is greater than the possible rewards it could get from a hunt, hence, a group of the same plesiosaurs vigorously assaulting it could successfully drive it away.

## Appearances

### Coasts

In the sixth and final segment of Coasts, in the shallow waters of Zealandia, large pods of *Tuarangisaurus* have come together to find the shoals of fish that gather in that area during the summer. One female, more sluggish than usual, lags behind the group, with only her two year-old calf to keep her company. Her laborious movement is noticed by a *Kaikaifilu*, which closes in on her, since she appears to be the easiest target to kill. She attempts to escape to deeper waters, while her calf charges at the mosasaur to harass and distract it.

***“ For the calf, trying to distract the mosasaur is a dangerous game. But it's buying time. The mother and calf are not entirely alone. These individuals may be related, and it's in all their interests to drive Kaikaifilu away. ”***

― **David Attenborough**, *Coasts*
Just when the calf got the mosasaur's full attention, enraging it enough to really commit to pursuing the juvenile plesiosaur, at least 4 - 5 of the members of the *Tuarangisaurus* pod circle back and assault the mosasaur, snapping at it and forcing it to leave. With the hunter gone, the sluggish *Tuarangisaurus*, which turns out to be pregnant, can finally give birth in peace.

### Prehistoric Planet: Uncovered - How Fast Was A Mosasaur?

  **How Fast Was A Mosasaur?**
**Subject**
The speed and acceleration of mosasaurs, as well as the means which allow them to perform the feats that make them quick, formidable, and powerful ambush predators.

**Experts**
Dr. Michael Habib, Kiersten Formoso
Footage of *Mosasaurus* from Coasts and Oceans, along with a brief moment of *Kaikaifilu*, are shown in this Uncovered segment, which is dedicated to discussing how fast a mosasaur could be.

***“ Mosasaurs were seagoing lizards. Think of a giant, swimming, whale-sized Komodo Dragon. Tapered snout, rough skin, four fins instead of normal limbs, and a long tail that would look a lot like a shark tail, but upside down. That's basically a mosasaur. ”***

― **Dr. Michael Habib**, *University of California*
Presented as the main focus is the largest mosasaur, *Mosasaurus hoffmannii*. The secret to the success of this ambush hunter is that it can move with incredible speed while it was only stationary moments before. Today, this is demonstrated by crocodiles, which have muscles that can deliver short bursts of tremendous power. Dr. Michael Habib, one of the show's consultants, brings up how mosasaurs may have bent themselves in a C-shape, then, in one sudden movement, push off of the water on the side of their bodies. As seen in modern-day fish, this "C-start" technique allows them to accelerate from a standstill to full speed in an instant. The suggestion is that mosasaurs use this same technique on a much greater scale. Using a 42-foot, 12-ton mosasaur for reference, the Prehistoric Planet research team ran a unique test four times to finally figure out exactly how fast can *Mosasaurus hoffmannii* actually swim.

***“ This mosasaur could probably clear 75% of its body length in one single second. That means if that mosasaur is 17 meters away from you, in one second, it will be 75% closer, and in the 2nd second, it would have surpassed you and probably eaten you along the way. ”***

― **Kiersten Formoso**, *University of Southern California*
The force generated by a mosasaur traveling at full speed is compared to the impact of a full-sized semi-truck, which, along with the mosasaur's powerful bite force, can prove immediately fatal.

***“ Mosasaurs could reach 30 miles an hour in as little as one second. This is what makes them arguably the ultimate marine predator of all time. ”***

― **David Attenborough**, *Prehistoric Planet: Uncovered - How Fast Was A Mosasaur?*
Going off of these calculations, *Kaikaifilu*, being 10 meters (33 feet) long, can cover a distance of 7.5 meters (25 feet) in one second, or 27 kilometers (17 miles) per hour. While this is the same as the top speed of *Tyrannosaurus*, *Kaikaifilu* can reach this speed in a single second and would have been able to maintain it for a comparatively longer time, while *T. rex* would likely tire out before even reaching its top speed. It is also possible that, given how it is only two-thirds the length and one-fifth the mass of *Mosasaurus hoffmannii*, *Kaikaifilu* may have been, in theory, faster than these calculations (which are meant for mosasaurs the size and weight of *Mosasaurus*) make it out to be. Conversely, it is also possible that the extra mass and the greater amount of muscles and generated power allow the larger mosasaurs to accelerate with such great speed, and, due to being smaller and thus, lighter and packing lesser or proportionately weaker muscles, *Kaikaifilu* may not have accelerated to such great speeds, meaning that the calculation only works for mosasaurs possessing a similar length and mass as *Mosasaurus*.

## References

1. ↑ 1.0 1.1 1.2 The Princeton Field Guide to Mesozoic Sea Reptiles
2. ↑ 2.0 2.1 As stated in Prehistoric Planet: Uncovered - How Fast Was A Mosasaur?
3. ↑ 3.0 3.1 Un nuevo mosasaurio (Squamata, Mosasauroidea) del Cretácico Superior de Antártica
4. ↑ 4.0 4.1 *Kaikaifilu hervei* gen. et sp. nov., a new large mosasaur (Squamata, Mosasauridae) from the upper Maastrichtian of Antarctica
5. ↑ Late Cretaceous winter sea ice in Antarctica?
6. ↑ Why *Tyrannosaurus* was a slow runner and why the largest are not always the fastest