regarding the Rhydon, looks good, though some of the lines are a bit wobbly, one of the teeth bending odly, for example.
aside from that, i'd say the shading needs a bit of work [something with that many edges and angles would be a shading NIGHTMARE for beginners X_X. i would think twice about shading something that pointy at the angle you did, so i'm not implying i could do a better job here]. the side facing the sun would be light, but the side in the shadows would have overlapping shadows. for example, the shadow of the side as well as the shadow of the spike/horn/whatever part you're working on at the time. as an example, the left ear would have the side facing the sun, light. the side facing away would be shaded, and the area around the base would have even MORE shadow, because it's got both the shade of not being in the sunlight, and the shadow of the ear itself, over it. like i said, a beginner's nightmare
as for Spinax's character, only comments i could give were to be shrink the stars and make them more frequent, maybe ditch the stars' 'arms', and make the waves slightly thinner, more frequent [i emphasise the term SLIGHTLY here. too much and it'd look like scribble], and melding into eachother, so it wouldn't be unusual for a wavy, sideways Y pattern to be made by two waves merging into one. gives the water a more natural, less solid look.
that aside, cool...