The Ferris Formation is an Upper Cretaceous (~67-66 Ma) to Paleocene (66-63 Ma), fluvial-deltaic geological formation in southern Wyoming. It contains a variety of trace and body fossils, preserved in sandy fluvial channel deposits and overbank units. Diverse vertebrate fossils have been reported from the formation. Supplemental Information

The Ferris Formation is up to thick in the Hanna Basin and represents a rapid accumulation of predominantly fine-grained sediment on a broad deltaic and fluvial environments. Some of the fluvial channels contain evidence of tidal influence and brackish water, in the form of tidal facies, shark teeth, and crustacean burrows, which demonstrates that the western shoreline of the Western Interior Sea was close in proximity to the Hanna Basin even during the latest Cretaceous. The local K-T boundary is contained within a sandy channel deposit made up of stacked bars. Reworked Cretaceous fossils are preserved at the base of the channel complex, associated with mud rip-up clasts, and Paleocene mammal fossils are preserved in the upper portion of the bar.

Fossils

Diverse vertebrate fossils have been reported from the Ferris Formation, spanning to from Lancian (Cretaceous) to Puercan (Paleocene). Systematics of mammalian fossil records are based on Lillegraven & Eberle (1999), while non-mammalian vertebrate fossil records are based on Wroblewski (2026).

Chondrichthyians Chondrichthyians of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images Dasyatis D. sp. Puercan Lonchidion L. selachos Lancian Myledaphus M. pustulatus M. sp. Orectolobiformes Indeterminate Restesia R. monocuspilatus R. americana

Actinopterygians Actinopterygians of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images Amiidae Indeterminate Lancian to Puercan Lepisosteidae Indeterminate Phyllodus P. paulkatoi Lancian Platacodon P. sp. Teleostei Indeterminate Lancian to Puercan

Amphibians Amphibians of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images Caudata Indeterminate Lancian Habrosaurus H. dilatus

Squamates Lizards of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images cf. Odaxosaurus cf. O. piger Lancian Squamata Indeterminate Lancian to Puercan

Testudines Turtles of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images Adocus A. sp. Lancian Baenidae Indeterminate Lancian to Puercan Basilemys B. sp. Lancian Chelonia Indeterminate Compsemys C. victus Trionychidae Indeterminate Lancian to Puercan

Choristoderans Choristoderans of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images Champsosaurus C. sp. Lancian to Puercan

Crocodylomorphs Crocodylomorphs of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images Alligatoroidea Indeterminate Lancian to Puercan cf. Borealosuchus cf. B. sp. Lancian Navajosuchus N. mooki Puercan

Dinosaurs Ornithischians Ornithischians of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images Ankylosauridae Indeterminate Lancian Some specimens originally assigned to Ankylosaurus and Edmontonia. Chasmosaurinae Indeterminate Originally assigned to Triceratops. Edmontosaurus E. annectens Nodosauridae Indeterminate Some specimens originally assigned to Ankylosaurus and Edmontonia. Ornithischia Indeterminate Stygimoloch S. spinifer Some specimens originally identified as thescelosaurids. Thescelosaurus T. sp.

Saurischians Saurischians of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images Acheroraptor A. temertyorum Lancian Some specimens originally assigned to Paronychodon and Saurornitholestes. Dakotaraptor D. steini Some specimens originally assigned to Aublysodon, Dromaeosaurus and Saurornitholestes. Deinonychosauria Indeterminate Nanotyrannus N. lancensis Specimens originally assigned to Aublysodon. Paronychodon P. lacustris Pectinodon P. bakkeri Some specimens originally assigned to Troodon. Richardoestesia R. isosceles Some specimens originally assigned to Saurornitholestes. Struthiomimus S. sedens Some specimens originally assigned to Ornithomimus. Theropoda Indeterminate Tyrannosauridae Indeterminate Tyrannosaurus T. rex

Mammals Eutherians Eutherians of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images Alticonus A. gazini Puercan Alveugena A. carbonensis Ampliconus A. antoni A. sp., cf. A. browni Arctocyonidae Indeterminate Baioconodon B. sp., cf. B. denverensis B. middletoni B. sp. Carsioptychus C. coarctatus Species originally assigned to Periptychus. Cimolestes C. sp. cf. C. sp. Lancian to Puercan Conacodon C. sp., cf. C. cophater C. delphae C. harbourae Puercan "Condylartha" Indeterminate Ectoconus E. cavigellii E. ditrigonus E. sp. Eoconodon E. sp. Gypsonictops G. sp., cf. illuminatus Lancian Loxolophus L. faulkneri L. sp., cf. faulkneri L. sp., cf. hyattianus L. priscus cf. L. sp. Puercan Maiorana M. ferrisensis Mimatuta M. sp. cf. M. sp. Mithrandir M. gillianus M. sp., cf. gillianus Oxyacodon O. sp., cf. O. agapetillus O. apiculatus O. priscilla Oxyclaenus O. cuspidatus cf. O. sp. Oxyprimus O. galadrielae O. sp. Palaeoryctidae Indeterminate Periptychidae Indeterminate Procerberus P. sp. "Proteutheria" Indeterminate cf. Protoselene cf. P. sp. Protungulatum P. donnae P. sp., cf. donnae P. gorgun P. sloani Valenia V. wilsoni Species originally assigned to Promioclaenus.

Metatherians Metatherians of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images Peradectes P. sp., cf. P. pusillus Puercan Peradectidae Indeterminate Lancian ProtalphadonP. lulli P. sp. cf. lulli Species originally assigned to Alphadon.

Multituberculates Multituberculates of the Ferris Formation Genus Species Location Stratigraphic position Abundance Notes Images Cimolodon C. nitidus C. sp., cf. nitidus Lancian EctypodusE. sp. A E. sp. B Puercan Meniscoessus M. seminoensis Lancian Mesodma M. ambigua M. formosa M. hensleighi M. sp., cf. M. garfieldensis M. sp. ?M. sp. Puercan Neoplagiaulacidae Indeterminate Lancian to Puercan PtilodusP. sp., cf. P. tsoiensis P. sp. Puercan Taeniolabis T. taoensis Valenopsalis V. joyneri Species originally assigned to Catopsalis.

See also List of dinosaur-bearing rock formations Hell Creek Formation Fort Union Formation

References

Bibliography