Thats a common pleco, the name for his tall fin is "sail fin" and his coloration is "marble". It's like saying "I have a long haired black cat" so it's a cat, and it has long hair, and it is black.
Yeah those guys max at like 30". They have teeth, large ones can and do attack swimming fish and eat them if they get hungry, and they are notorious jumpers.
LFS will call pretty commons "fancy plecos" "fancy commons" "marble plecos" "sail fin plecos" etc..... They just want a reason to call it something other then common....
To me it seems a bit like calling that long haired black cat a Persian... even though it is just a regular cat with long hair.