The separation between the head and body in the sprite is definitely not evident. The concept is pretty awesome, but with the head-on view it doesn't translate well, seems to me. I think it's partly 'cause you shaded everything like it's on the same plane. Like, okay, you've got shading, lightsource, etc. but you really have to make that distinction between what's in front and what's behind. The head should cast a shadow on the body, etc.
On the animation, it seems rather stiff for such an awesomely organic creature. So mechanical, see? Just straight down. I would suggest having, rather than a straight-down, straight-closed, strike-bite, maybe give him some swing on the z axis and then have him do more of a scoop motion, see? Like, swing back, then real quicklike, forward and up in an arc towards the viewer. Also, maybe give the lower jaw/lip some opening too, instead of just having the top widen. Makes it look weird, you know? Less menacing. Things don't really open their mouth from the top, you know? So yeah.
