Skeletal Remains of various, mostly extinct species can be found in the game. The majority of these skeletons are found in the Lost River, aside from Reaper Leviathan skeletons which are found in the Inactive Lava Zone and the Mountains corridor.
Some skeletons can be scanned, doing so will provide additional story information, or other information.
Skeletal Remains Found in Alien Habitat
This large creature was kept in the large aquarium of the Disease Research Facility for a long period of time for testing purposes. The skeleton is very odd in appearance, having a solid exterior shell, as well as an interior skeleton. The PDA notes shared skeletal traits with the Biter. It also states that this creature was a carnivorous life form.
The skeletal remains of a vast predator, discovered inside an artificial habitat at the alien research facility.
Ancient Fossilized Skull
This huge skeleton is found outside the Lost River Laboratory and is surrounded by spotlights and cables. This species is presumed extinct. The skeleton is the only one known to exist and is approximately one million years old. It appears to be some sort of huge carnivorous life form. The skeleton is composed of many bone plates. Running parallel on down either side of the skeleton are twelve large holes, the purpose of which is unknown. It has six eye sockets and many sharp teeth, each tooth being larger than the Player.
This skeleton is large enough that the player can swim through the gaps left by its missing teeth.
The skull of a million year old armored carnivore. Projections suggest this lifeform would have been larger than any living specimen encountered on the planet.
The oceans of 4546B must have been very different to support lifeforms of this size, with more open geography and many more lifeforms in the leviathan range.
Reaper Leviathan remains can be found on the floor of the Inactive Lava Zone, and within the Mountains corridor. They are either found as whole skeletons, or just skulls. The Reapers came to be in these locations due to Sea Dragon Leviathans making infrequent trips to the surface to hunt them, and then bring them back down to eat.
This leviathan is not adapted to live in volcanic environments.
Sea Dragon Skeleton
This skeleton is found in the Lost River Junction. It belonged to a Sea Dragon Leviathan that attacked the Disease Research Facility in an attempt to retrieve an egg belonging to it, that the Precursors had taken in the hope that it would it would reveal the hatching mechanisms of Sea Emperor Leviathan Eggs, likely due to the similar physical appearances of these two species, suggesting they share a common ancestor. The Sea Dragon's attack on the facility destroyed it, but also caused fatal head trauma to the Sea Dragon; it died not long after the attack. The remains are approximately one thousand years old.
The semi-intact skeletal structure of a leviathan class predator.
This skeleton is enormous and ancient, approximately three million years old, found in the Bone Fields. The skeleton belonged to an enormous, eel-like super-predator, dwarfing both the Sea Dragon Leviathan and Sea Emperor Leviathan, despite only being around one third of the whole skeleton. The remains consist of a huge, reptillian-esque skull and sixteen pairs of huge ribs. The skeleton is covered in flora and coral. The skull is so large that a Cyclops can fit inside its jaws. The Precursors were also studying these remains, as evidenced by small, angular indentations on the ribcage, as well as the Disease Research Facility being partially set up to study it. A smaller variant of this creature's skull can be found in the Ghost Forest.
The complete specimen would have been an estimated 1300–1500 meters long.
The fossilized remains of a seemingly extinct super predator. Its sheer size would have prohibited it from entering such an enclosed space, suggesting the geography of the planet has shifted around it over time.