An ancient mammal that emerged from a large cave discovered at the Kitayama Tunnel construction site in the third construction zone of the Expressway. Gomess' scientific name is "Gometius". It is carnivorous and rabid, attacking its enemies with its sharp and huge claws, fangs, and its tail. It is the natural enemy of the primitive monster bird Litra.

Gomess had been hibernating for a long time in the depths of a large cave but was awakened by a rise in underground temperature due to a tectonic movement, and was discovered by a miner who dug the cave.

Later, when Yuriko Edogawa and Jun Manjome enter the tunnel for an interview and are trapped in the cave by a landslide caused by an earthquake, they become aware of its presence, Gomess relentlessly track them down. When Litra, which had just hatched from an egg unearthed in a large cave, attacked them from above, Gomess fought back with its tails and fangs, but in the end died after being exposed to Litra's "Citronella Acid".