Hell Creek Formation picture. Credits to Anky-man
The Hell Creek Formation is a rock formation that houses mostly Late Cretaceous aged rock, dated at the Maastrichtian stage. It was named after the exposures studied at the Hell Creek it was found near. It overlies the Fox Hills Formation and underlies the Fort Union Formation. The K-Pg Boundary is situated near it, preserving flora and fauna shortly before the K-Pg extinction event.
Members of Hell Creek[]
Many animals have been found in Hell Creek's rock layers, and is rich in biodiversity. Hell Creek, as one of the final preserved time periods before impact, has a very high importance. Below will be all listed confirmed genera found from the formation, but indeterminate remains will be mentioned in their respective sections. Many genera are still extant to this day, so only the extinct species will be listed when possible.
Invertebrates[]
Mollusca[]
Several bivalves make up the majority of mollusk genera found in Hell Creek, along with two genera of ammonites and one freshwater snail.
- Corbicula
- Sphaerium beckmani
- Obovaria pyramidella
- Pleiodon (indeterminate species)
- Plesielliptio
- Plethobasus (P. aesopiformis and P. beisopoides)
- Pleurobema cryptorhynchus
- Proparreysia (nine species)
- Quadrula cylindricoides
- Rhabdotophorus
Insecta[]
Multiple indeterminate specimens of flies, dragonflies, and damselflies have been found in Hell Creek's amber, but unnamed. Currently only one species has been named.
- Cephaloleichnites (ichnotaxon of leaf beetle)
Fish[]
Several genera of fishes have been described from Hell Creek, ranging from sturgeon to sharks, with some genera still extant. This section is separated by bony fishes (Osteichthyes) and cartilaginous fishes (Chondrichthyes).
Chondrichyes[]
- Chiloscyllium (indeterminate)
- Galagadon
- Lonchidion
- Myledaphus
- Protoginglymostoma
- Restesia
Osteichthyes[]
- Acipenser (A. amnisinferos, A. eruciferus, and A. praeparatorum)
- Anchiacipencer
- Belonostomus
- Coriops
- Cyclurus
- Lepisosteus occidentalis (nomen dubium)
- Melvius
- Phyllodus
- Paleopsephurus
- Paralbula
- Parapsephurus
- Platacodon
- Protoscaphirhynchus
- Pugiopsephurus
Anklyosauridae/Nodosauridae[]
Pachycephalosauridae[]
Ceratopsia[]
- Leptoceratops
- Tatankaceratops
- Torosaurus
- Triceratops (T. horridus and T. prorsus)
Ornithopoda[]
- Edmontosaurus
- Thescelosaurus (T. garbanii and T. neglectus)
Theropods[]
- Trierarchuncus
- Tyrannosaurus
- Nanotyrannus (N. lancensis and N. lethaeus)
- Struthiomimus
- Ornithomimus
- Anzu
- Eoneophron
- Acheroraptor
- Avisaurus
- Brodavis
- Dakotaraptor
- Magnusavis
- Paronychodon
- Pectinodon
- Potamornis
- Richardoestesia
- "Styginetta" (nomen nudum)