I just looked up a lot of squalifoma profiles and everything but the tail matches. the the bottom half of the tail is longer than the top on all squaliformas, where as both parts of the tail are the same size on my pleco
My first thought was a Hypostomus but I think the caudal trunk is too skinny and elongate for them. I think it should be either be Squaliforma or Aphanotorulus.
I think the tail thing you describe is just due to the nature of a closed/open caudal fin.
What was called the Cochliodon genus was also a thought but like most plecos ID,s get totally blasted every now and again and we poor hobbyists are at a loss to keep up