Reptilicus

A fair-to-poor monster film has a group of oil drillers coming up with the mangled tail of some prehistoric beast (the film's most gruesome and best scene). Sent to a famous professor for study, the tail starts to regenerate and grows into a fierce beast that wreaks havoc on Copenhagen. American troops can't stop the beast but are able to force it into the water. A depth charge severs its feet, but it still keeps up the devastation. Finally, a deadly drug is shot into the monster, and it seems to perish. But those feet are still around and growing by the minute.