Spawned from here
It's debatable.
1. While the Japanese name for BW Basic Megatron is "Megalligator," the Japanese word used to describe the alt mode in the tech specs and packaging is "wani", which the Japanese use to refer to anything from the Order Crocodylia -- the Japanese word doesn't specify which family, although it is more often associated with crocodiles.
2. Hasbro's packaging says "Crocodile turns into evil Predacon commander!"
I know that the mould is closer to an alligator than to a crocodile even though Hasbro says it's a crocodile. Some would argue that it's closer to a caiman than an alligator. But then again, Snarl's beast mode is closer to a dunnart than a Tasmanian Devil, yet HasTak says it's meant to be a Tassie Devil.