More than one Monster Theory

I have gone to see the movie a couple of times and this is just a theory but has anyone entertained the idea of more than one monster in the movie? The reason I ask is that the monster at the end seemed smaller and almost looked nothing like the monster that pulverized manhattan. Another thing is the bridge scene when the tentacle destroyed the bridge....the monster in Manhattan didnt have any "visislbe" tentacles. Lastly the statue of liberty sits in the water....so the monster went to Manahttan and then got back in the water to destroy the bridge then back out to keep destroying manhattan? Just some observations and totally loved the movie