Evolving Life

These creatures appear on earth through transdimensional portals or other means. They start out as simple sing-celled organisms but they grow and progress rapidly, evolving into higher and higher forms of life, eventually into sauropod-like monsters and other imitations of life on Earth. 
References:
-http://www.imdb.com/title/tt0251075/
-http://www.imdb.com/title/tt1470827/
Category:Life