The Dragonsaurus is a monster from prehistoric times, surviving in the depths of the ocean. Overtime it fed on the oil quantities in the Earth to survive millions of years before resurfacing in the present day.
The Dragonsaurus is massive sea creature with seven tentacles that have serpent-like heads. Its one real head however is located on the center of its body, appearing as a lump with a terrifying face.
The Dragonsaurus has the unique ability to feed on oil which allows it to survive long periods of time and grow larger and stronger in size. In battle it mainly uses its serpentine tentacles that can extend to long distances to attack enemies, which can also create hurricane force winds. It posseses an extremely high healing factor, allowing it to regenerate its tentacles in a matter of seconds. Its resistance is no joke eiter, the Dragonsaurus being immune to electric and acid-based attacks, incredibly resistant to beams and it can absorb projectiles like missiles into its body where they fail to detonate. It also has the ability to levitate when going towards land.
In the Kessen! Daikaiju crossover, the Dragonsaurus heads for Tokyo with three super robots Grendizer, Great Mazinger, and Getter Robo G deployed to fight it. The three robots were having a tough time fighting the mosnter, and matters only got worse when Boss Borot showed up and got swallowed. The oil within the awkwardly moving robot made the Dragonsaurus stronger. The Great Mazinger made an opening allowing Boss Borot to escape. Knowing the massive amounts of oil within the Dragonsaurus, the Getter Dragon used the Shine Spark to ignite the oil, which caused the Dragonsaurus to explode.
The Dragonsaurus appeared as the final enemy of the series, alongside Dr. Hell. It was first foretold by Aila Mu, who was speaking to Jun Hono through her dream, explaining that it was the force that destroyed the Mu kingdom many years ago. Dr. Hell had some of its Mechanical Beasts have beacons set up to guide the monster to the Tokyo Bay. The Mazinger Angels were dispatched to handle the situation. However, with Dr. Hell's Mechanical Beasts getting in the way, and the Dragonsaurus itself being a force to be reckoned with it looked like a losing battle. However, Minerva X, Diana A, and Venus A assumed their more powerful forms and used a joint attack to destroy the Dragonsaurus at its real head.