Did you know fantastic help is an anagram of Planet Catfish? This forum is for those of you with pictures of your catfish who are looking for help identifying them. There are many here to help and a firm ID is the first step towards keeping your catfish in the best conditions.
Two days ago I bought a fish under the name 'Ancistrus', after some googling I came to the conclusion that it is most likely to be a 'regular' Ancistrus cf_cirrhosus. But he/she has a white stripe at the end of the caudal fin what made me think about the Dolichopterus, so just to make sure hopefully you can clear things up. This is the picture I made, hopefully it is clear enough, if not please let me know and I'll try to make more when he reveals him/herself.
It is most likely a common Ancistrus. The young will have the white along the fins, and as they grow it will fade out.
If it were true dolicoptrus, it would likely be very expensive and not thriving in the store, unless it is an exceptional lfs, as they have very specific needs that most stores (at least in this area) will not be able to maintain.