08/14/2026
Our fifth and final Beach Buddy is Phareodus encastus. A species of freshwater bony fish from the Eocene, P. encastus fossils are found in the Green River Formation of Wyoming, a former lake basin famous for exceptional preservation of fossils.
The name Phareodus means “to have teeth”, and these fish certainly did. They used their rows of chompers to hunt smaller fish and insects in the mid to deep waters they inhabited. These fish used their backloaded, backward-facing fins to dart forward, either to catch prey or escape predators. With much of their habitat being mountain lakes, long term hiding was rarely an option, so rapid bursts of speed would have suited the species well.
Modern relatives of Phareodus have been recorded as using their teeth as bars, carrying eggs or hatchlings around safely in their mouths. Mass mortality specimens of juvenile Phareodus supports the hypothesis that they traveled in groups when young, though the lack of such fossils displaying adult individuals suggests they lost their schooling tendency after maturing.
If you have ever had the experience of taking a group of kids to a waterpark, you can likely relate to this fishy chaperone. So swing on down to the museum and see the fossil in person, before heading to the waterslides.
📷 Phareodus fossil. Wyoming.
