Anguirus is a fictional monster who appears in movies in the "Godzilla" series. He is a very large, mutated ankylosaurus. He first appeared in "Godzilla Raids Again", a 1955 kaiju movie from Toho Studios. He was the first monster that Godzilla fought against. Since then, he has fought with Godzilla against stronger monsters who put the Earth in danger. This makes him one of Godzilla's most trusted allies.