so much to learn...
Your details are fine, the main problem is the anatomy. I know this is not a real animal, but it's based on real life references, and this is why the original concept art look so good. Type crocodile anatomy on google, and check how the legs are made compared to the one we have as human. Crocodile walks on their fingers, not hand or feet like you did on your model. Plus, the foward articulations look too much like an human arm, take the midle joint, it looks like an elbow on your model, when in real life, its a wrist. Making those distinction will help the overall realism of your creature.