Platylithax robusta, periotic , porpoise ear bone

This is a really close match for Platylithax robusta, a taxon which Kellogg (1931) named based off of an isolated periotic from Sharktooth Hill. According to Barnes and Mitchell (1984), this is one of the rarest species of odontocetes in the Sharktooth Hill bonebed To be more specific: at the time of writing, Barnes and Mitchell stated that the only known specimen of Platylithax was the type specimen reported by Kellogg.