Hi! Thanks for the comment. I'm new on pixel art (I started like a month ago xD)  so I will practise the things you said. Thank you a lot. Also, I thought about the animation of the jaw, but I absolutely  forgot xD. Well, anyways, thank you. I'll keep practising as much as I can :D

For the challenge, I presume? 

I like this. My only nitpick though is the fish skull; it feels rather solid and stiff, as if it's a cardboard puppet being pulled up and down. Having the lower jaw bob with momentum (open as the skull goes up and close as the skull goes down) should help make it feel more realistic 

I also feel like it could use a tad bit more polish and maybe a little cropping, though the latter is just me as I personally don't like having lots of empty unused space unless it works with the piece lol.