A lot of Pterygoplichthys sp. including pardalis and gibbiceps are considered common. Alas, I hate common names as they offer little validity to the actual identification of a particular species.
I picked up a "common pleco" tonight because when I was getting feeders I found one that was jet black no dots and very pale brown eyes and very extended tailfin
will have to see what it turns out to be
my last impulse "common pleco" purchase was a bristlenose who is presently growing out in my 140g