Inox (Inoculopalus edax, meaning Gluttonous Swamp-dweller) measure 12-18 feet in length.
A relic of a long-gone age, the large arrowheaded tetrapod Inoculopalus had remained largely unchanged since the Permian age. The wide meat eaters preferred to lurk in the stagnant pools and weed-clogged marshes of Skull Island's waterways, where murky water and floating scum helped mask their presence. Oversized relatives of modern salamanders and frogs, they were ambush predators, taking fish, wading birds, or anything small enough to fit down their throats.
Despite possessing legs, Inox preferred not to leave the water unless compelled to do so, either by lack of food or shrinking territory in times of drought. The ungainly animal was capable of hauling itself short distances over land but was vulnerable out of the water.
In their tadpole form, young Inoxes lived in muddy creek beds, surviving on a mixed diet of carrion, insects and grubs, small fish, and algae. They appeared similar to the adults but lacked back legs and the distinctive triangular skull until fully mature.