In today's nature animals that can eat from trees and grass normally are four legged like a giraffe or elephant and have teeth for tough vegetation. What would the teeth be good for and would vegetation alone be enough to sustain a animal of that size. The shape of the head and only having front teeth seem that it to pull soft water vegetation in water, swallows its food mostly whole while using it teeth for sifting or catching fish. Flamingos have a similar head structure and sifts water. I imagine land was lush including the swamps would be teaming with life. It would help to know its environment.
The tail is for protection usually most reptiles with long tails do not use them offensively.
