G.M.
Both my boys transitioned from adventuresome eaters with huge appetites to toddlers with a more limited taste and appetite at right around that age. I read somewhere that one should average a toddler's food intake over a week before getting worried about it, so I just tried to relax.
I know that dinner is kind of an institution in the US and that we all want to teach our kids to eat a family meal in the evening, but I think that it's healthier for dinner not to be the central, biggest meal of the day. I've tried to back off the eating part of our dinner routine and focus on the social part. That way, I have no 'food agenda' and I am more likely to not be stressed by my kids grazing all evening (on healthy foods) rather than sitting down to an evening meal.
And, I second the opinion that he probably wants some independence. My kids were self-feeding by about 15 months. I put down a plastic tablecloth on the floor, high chair on top of that and let them go nuts. They love playing and exploring with their food. And enough actually gets in their tummies! Remember that his stomach is only as big as his fist.
Hope this helps.