It's a really unwell and deformed Synodontis catfish. It has no dorsal fin and has pits all over its face. It's tail is clamped and the fish is really skinny.
Try feeding it on prawn, fish, frozen (but defrosted) bloodworms, brineshrimp and mysis shrimp. Feed it 3-5 times a day for a month then reduce feeding to 2-3 times a day for a month and then reduce it to 1-2 times a day from then on.
Do a 50-75% water change and gravel clean the substrate every day for the first month then reduce it to 2-3 times a week for a month, then reduce it to once a week.