Eocene Green River Mioplosus
Mioplosus labracoides
Green River Formation
Middle Eocene
Lincoln County, Wyoming
This is an outstanding example of the species from the Fossil Butte Member of the Green River Formation. This specimen has excellent preservation and detail for this locality. Often Mioplosus specimens have significant disarticulation but this example has perfect articulation. The fish body is 26 cm long. There is no repair or restoration.
Mioplosus is the largest perciform fish found in the Green River Formation. The genus makes up about 2 to 4 percent of the total fish fauna. Mioplosus is easy to distinguish from the other perciform genera in the formation because of its very elongate fusiform body shape, the presence of two distinct dorsal fins, and a moderately forked tail fin. The maximum size for this species is about 20 inches but very large examples are quite rare. Mioplosus was evidently a very predaceous species as indicated by dozens of known specimens with fishes in their jaws or stomachs. Even as very your recently hatched individuals, this species was already cannibalistic, feeding on other small Mioplosus.