the inside of its mouth is also too strikingly bright in contrast. dull that pink down a bit and it won't be such and eyesore.
and if you know me well, you'd know i would gripe about the black you used. so i think you should lighten it up just a bit. and give him some highlights! rhydon is very metallicy give his armor some shine!
while you're on the right track with the head shape, it looks very uneven...i dunno, it just looks...off.
and those legs, they should be stretched out just a bit, they're way too close together. rotate them out more so that they can actually support his weight.