Arctovish is a fish-plesiosaur hybrid fossil Pokémon. The plesiosaur half is colored blue and white. Arctovish has a blue tail with a fin on top. The flippers are colored blue with white patches on the end and with white spots. The fish half is applied upside down. It has a round blue head with black rectangle pupils, and the mouth is located on top of its head. It has white fins connected to its fish head.
It has trouble eating due to its mouth being on top of its head, even though it captures prey by freezing its surroundings. The skin on Arctovish's face is impervious to attacks. It allegedly became extinct despite this due to breathing difficulties, though this is likely not the case due to Arctovish being combined from two separate Pokémon that each had their niches before going extinct.
Arctovish, like its counterparts, may be based on the concept of chimera in paleontology, which refers to fossils reconstructed from multiple different species or genus of animals, resulting in an inaccurate and mistaken understanding of the animals's biology. In the case of Arctovish, its top half appears to be based on the fish Dunkleosteus though the frontal pair of fins resemble those possessed by lobe-finned fish such as coelacanths rather than the fins of Dunkleosteus. The upper half may also be based on the Ainiktozoon, an arthropod fossil discovered in Scotland which was reconstructed upside-down. Its bottom half appears to be based on an aquatic reptile, like a plesiosaur, mosasaur or ichthyosaur. Arctovish and its counterparts may also reference the Crystal Palace Dinosaurs, a series of scientifically inaccurate dinosaur sculptures displayed at the Crystal Palace Park.
The Pokédex entries for all the Galarian fossil Pokémon mention them being the cause of their extinction, which may be a reference to the outdated hypothesis that the dinosaurs were evolutionarily inert, which made them get bigger, stupider, and more sluggish, to the point they couldn't sustain themselves.
Arctovish being unable to breed could be a reference to cross-bred animals, which are born infertile (unable to produce offspring).
Arctovish may be a combination of arctic, fish, and possibly vicious or Ordovician.
Uochilldon may be a combination of 魚 uo (fish), chill, and -don (common suffix in dinosaur names derived from the Ancient Greek word for tooth).