Belchbeast (Gastrotherium ursamimus)

When living in harsh environments with little options for a sustainable food source, a thick layer of fat is one of the best options an animal can opt for. Though usually associated with marine tetrapods (as it aids in buoyancy and keeping warm), blubber is also an efficient tool for land tetrapods that live in environments with temperature extremes. Deserts and desert-like conditions often bring forth animals which sport this excess adipose tissue due to the lack of food, which results in animals eating in large amounts at one point in time and using their fat to sustain themselves for what could be several months. Skull Island's dry semi-desert, unsurprisingly, is home to a creature that follows this evolutionary trend; the unflatteringly-named Belchbeast (Gastrotherium ursamimus).

The Belchbeast is a large multituberculate that, true to its species name, shares many traits seen in bears, including an omnivorous diet, semi-dexterous front paws, massive amounts of hair, the ability to stand upright to intimidate foes, and a vast amount of fat to live off of in a biome where food can be scarce during the island's dry season. This primitive mammal can reach sizes also attained by adult sun bears, and like the Sun Bear, it even has a long, sticky tongue to help it feed on insects (and even some small tetrapods) found in the holes of spiny trees. Though this beast is a generalist feeder, it seems to take notable preference to succulents, which are full of precious water and nutrients to help it in trying times.

Belchbeasts get their name from one less-than graceful behavior of theirs; their extremely loud belch-like calls. These beasts have a wide range of sickening vocalizations, each one having a different purpose. Louder calls are meant to call out for mates (they live in monogamous pairs), while quieter (a very liberal use of the word) calls are used during more direct confrontations with predators, rivals, potential mates, or just friendly communication with other members of the species.

Author's Note: The Belchbeast is loosely inspired by a crocodylomorph from The World of Kong: a Natural History of Skull Island labeled the Bear-Croc, which also produces belch-like vocalizations.