Lets get things straight shall we?

let this get straight out the gate... whoever said that was Gojira lol

In this movie Gojira isn't the species, it's that one individual creature.

While the bones could have belonged to an ancient member of that species, and the spines could have fallen off or been lost to time, I definitely agree that it's too long and skinny.

So basically, I agree with your main point, but I don't jive with your logic.

i think its manda

When Dr. Graham asked if it was Godzilla Serizawas exact words were: "No, something much older."

I just like to tell myself it was one of the Ghidorah heads :D

http://www.scified.com/site/godzillamovies/igns-godzilla-set-visit-reveals-new-stills-potential-spoilers--godzilla-easter-eggs

See after reading this months ago , I tend to disagree with anyone who says it is not a Godzilla Skeleton.

Note : Please read the line and paragraph under the first picture after clicking link.

People it is the skeleton of one of the Shinomura. 

In the DVD special features, they confirm that it is in fact a Godzilla skeleton.

^I wish it was clearer in the movie. It might've made the vendetta Godzilla has for the MUTO a bit stronger. "This is much older," is such a vague line and lends people to wonder if it was a Godzilla or not. It's some of the weakest exchanges of dialogue in the film.

Yeah i agree, in the dvd extras they do say that it is indeed the bones of godzilla. So, that really means that even though it was "much older" that godzilla in the movie wasn't the oldest of his species.

The closest thing said in the movie to suggesting that the skeleton is a Godzilla is just when Serizawa says it's "another giant creature, like Gojira." That line could mean that it's any other giant monster from the same period, not specifically a Godzilla. Either way, the special features have confirmed that it is Godzilla. If Legendary so chooses, the skeleton could be a setup for Mechagodzilla in the third film.