Reptilicus

Danish miners dig up a section of a giant reptile's tail from the frozen grounds in Lapland, where they are drilling. The section is flown to the Danish Aquarium in Copenhagen, where it is preserved in a cold room for scientific study. But due to careless mishandling, the room is left open and the section begins to thaw, only for scientists to find that it is starting to regenerate.
Once fully regenerated from the tail section, Reptilicus goes on rampage from the Danish countryside to the panic-stricken streets of Copenhagen before finally being killed with poison by ingenious scientists and military officers.
However, the monster's foot is not destroyed and sinks to the bottom of the sea...