Phareodus was a predatory fish classified in the same family as the living arawana of South America (family Osteoglossidae or bony tongue fish). Two species are known from the Green River Formation. P. encaustus was larger (up to 75 cm) and more elongate, while P. testis had a shorter body profile with a deeper belly and grew up to 38 cm in size (Grande, 1984; 2013). Phareodus fossils have been found with remnants of Knightia, Mioplosus, and Priscacara fish in the stomach or mouth. The genus has been reported from Cretaceous rock in India, Paleocene rocks in Bolivia, Mexico, and USA (Washington), and Eocene rocks of Wyoming, Australia, and Europe (Paleobiology Database, n.d.). This specimen is from the Fossil Lake basin, near Kemmerer, Wyoming, and shows the characteristic large, mosaic-like scales with a reticulate pattern of lines typical of bony tongue fish.

References:

Grande, L., 1984. Paleontology of the Green River Formation, with a review of the fish fauna. Geological Survey of Wyoming, Bulletin 63, p. 333. (1st ed. 1980.)

Grande, L., 2013. The lost world of Fossil Lake: Snapshots from deep time. University of Chicago Press. p. 425.

Paleobiology Database, No date. Phareodus. Available at: https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=53975 (Accessed: March, 2025).