Pen Formation
The Pen Formation is a Campanian-age geologic unit in the western United States.
Vertebrate fauna
Sharks are well known from the Pen Formation.Lonchidion selachosSqualicorax kaupiCretorectolobus olsoniIschyrhiza miraScapanorhynchus texanusS. raphiodonCretolamna appendiculataOther fishes include Xiphactinus, the ray Ptychotrygon, and gar. The nodosaurid ankylosaurs Acantholipan and CPC 273 have also been found in the Pen Formation.