Back when I started keeping fish about forty years ago the "Common Plecostomus" were actually Hypostomus. When Pterygoplichthys gibbiceps came in they were called Red-spot Plecs. Now it appears to have shifted to Pterygoplichthys being called "Common Plecostomus" instead. The one in this photo clearly isn't a P. gibbiceps but you'd really need a good view of the dorsal fin to tell which genus it is.
@Chlidonias oh yeah definitely not P. gibbiceps- much more likely to be P. pardalis, P. disjunctivus or P. multiradiatus. Invasive populations derived from aquarium trade dumps/releases have been shown to largely be those species, and hybrids thereof.
I'll dig the papers out later when I get time to look.