Of course, I have only ever touched Diplomystus dentatus  from the Green River Formation, Eocene. The head of your critter looks like a familiar diplo, but obviously, "shorter" and deeper bodied for its size. These traits to my eye are so exaggerated that it makes me question the legitimacy of the specimen. In addition, the spine of the dorsal fin looks preternaturally long for the total size of the critter. But having no experience of fish from that location or age; I will have to wait for thos