Phareodus encaustis is an osteoglossid (arowana) that comes from the Eocene of the Green River Basin formation in Wyoming. I've also attached a jaw from a larger specimen than the one photographed (really wish I'd found the complete fish)
Here's another Osteoglossid (arowana) called Phareodus testis. Climate changes killed off the 2 known US-native aro species. Darn the bad luck. This one is also from the Eocene (50 MYO) Green River Basin formations of Kemmerer, Wyoming.