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Very young fish (27mm) in which the scales have not yet ossified. Juvenile specimens of Diplomystus dentatus can easily be mistaken for juvenile specimens of Notogoneus osculus. But juvenile Notagoneus can be easily recognized by the larger skull and the position of the anal fin, which is set far back. For comparison a specimen of a juvenile Diplomystus dentatus preserved on the same slab: Taxonomy from Fossilworks.org. Revised generic diagnosis from Grande and Grande 2008, p. 10. "†Notogoneus differs from all other genera in the family Gonorynchidae by the following characters: (1) the subopercle bears a series of deep clefts along its posterior margin; (2) the first and second hypurals are not fused to each other; (3) the parhypural is not fused to the vertebral column; (4) the first and second hypurals are not fused to the vertebral column; and (5) scales in adults are nearly the length of a centrum. Also, the frontal is a paired element in †Notogoneus (vs. median in Gonorynchus)." Line drawing from Grande & Grande 2008, p. 4: References: Cope, E. D. (1885) Eocene paddle-fish and Gonorhynchidae. American Naturalist, 19:1090–1091. Woodward, A. S. (1901) Catalogue of Fossil Fishes in the British Museum (Natural History), Part IV 1-63. Hay, O. P. (1902) Bibliography and Catalogue of the Fossil Vertebrata of North America. Bulletin of the United States Geological Survey 179:1-868. Grande, L. and Grande, T. (2008) Redescription of the type species for the genus Notogeneus (Teleostei: Gonorhynchidae) based on new, well-preserved material. The Paleontological Society Memoir 70:1-31 [M. Uhen/M. Uhen]