When a village in San Javier, Peru fell under attack by an enormous beast, G-Force arrived to invesitgate, assuming it was Godzilla's doing. They held onto this assumption until they discovered a massive hole tunneled into the earth by the responsible creature, which Burton Helzer jokingly named "Burtannus Rex". Kino and Také investigated the tunnel to see if they could locate the monster. They eventually came across a pair of creatures nearly twenty feet tall. They realized the two were only babies, and were immediately greeted by their mother, who was easily as large as Godzilla. Stunning the subterranean beast with a million candle-power flashlight, Kino and Také were able to make their escape from the tunnel.
Meanwhile, as all this was happening, Godzilla had arrived in the area, searching for Burtannus. Digging into her tunnel from under the ocean, Godzilla forced the mighty parent and her children out into the open sea. Burtannus struck first blood in the fight, impaling Godzilla with her spiked snout. Godzilla responded by biting Burtanus' face then firing his atomic ray into the wound. Relatively unharmed, Burtannus responded by stunning Godzilla with an electric shock, then knocking him off his feet with a slam from her mighty tail. With Godzilla distracted, Burtannus decided to leave the fight behind and escape with her children, swimming off to parts unknown.
Burtannus' skin is armour-like and quite tough. She has a large, powerful tail capable of battering opponents, and it is also covered in spikes. Her beak is quite sharp and capable of piercing even Godzilla's hide. Her greatest weapon, however, is the ability to send out a powerful electrical current from her snout spike, an attack strong enough to momentarily stun Godzilla.
The creature Burtannus was named after Burton Helzer, a senior member of the kaiju research team G-Force.