Jacknife Cory. I just made that name up as I typed this.
But the fin does fold like a foldable knife - reminiscent of the marine Jackknife Fish shown above. As well as C. pulcher there are a few C-numbered fish that are similar; if you are going to order from a list sight unseen, get a picture first.
"Lovely pair of Corydoras serratus (Sands, 1995) a species discovered alongside Corydoras duplicareous found during my Upper Rio Negro field research, and described in my doctoral thesis." - David Sands
Mistakenly sold as C. punctatus, which actually looks like C. julii; also confused with C. reticulatus which always has clearly marked dark spot is on the dorsal fin which is absent in C. sodalis.
