Although †Hiodon rosei (Hussakof), an extinct species of mooneye, has been known of for over a century, little in the way of its ecology or life-history has been studied. It is a common fossil in the McAbee site, a lakebed dated to the Eocene epoch. Various fossils collected from the sites around the Eo-Thompson basin (including McAbee) were analyzed for standard length in an attempt to generate age classes. Missing standard lengths were extrapolated from proxies determined by regression analysis. The distribution of sexes among the various fossil localities was also analyzed. Furthermore, to support hypothesis development about the ecology of †H. rosei, a literature review was undertaken. The fossils from the Eo-Thompson basin range from less than 1 year to over 4 years of age, with the majority being between 1 and 3 years of age. There was no difference in the distribution of sexes within the McAbee site or between the sites of the Eo-Thompson sites studied. †Hiodon rosei appears to be an opportunistic insectivore, probably feeding at night. It may have spawned in rivers or shallow water, and matured around 1 year of age. Much research is still needed and a promising start is to collect further samples at the Eo-Thompson sites.
