The Sundance Formation is a western North American sequence of Middle Jurassic to Upper Jurassic age Dating from the Bathonian to the Oxfordian, around 168-157 Ma, It is up to 100 metres thick and consists of marine shale, sandy shale, sandstone, and limestone deposited in the Sundance Sea, an inland sea that covered large parts of western North America during the Middle and early Late Jurassic.
Geology The Sundance Formation underlies the western North American Morrison Formation, the most fertile source of dinosaur fossils in the Americas, and is separated by a disconformity from the underlying Middle Jurassic Gypsum Springs Formation.
Fossils The Sundance Formation is known for fossils of an extinct species of marine cephalopod, the belemnite Pachyteuthis densus, as well as several extinct species of oyster, including Deltoideum, Liostrea, and Gryphaea nebrascensis. Other common invertebrates include crinoids, echinoids, gastropods, insects, ostracods, and foraminifera.
Fossil dinosaur 'footprints' on an ancient ocean shoreline are preserved in the formation and protected at the Red Gulch Dinosaur Tracksite, located in the Bureau of Land Management Red Gulch/Alkali National Back Country Byway, near Shell in Big Horn County, Wyoming.BLM−Bureau of Land Management, Wyoming Office: "Red Gulch Dinosaur Tracksite" website, info, maps, photo gallery, accessed 8.21.2015
Two unusual trackways from the formation are not easily identifiable to taxonomic group, though one could have been from an injured pterosaur.
Paleobiota
Reptiles
Genus Species Member Material Notes PteraichnusLockley, M.; Harris, J.D.; and Mitchell, L. 2008. "A global overview of pterosaur ichnology: tracksite distribution in space and time." Zitteliana. B28. p. 187-198. . P. stokesi Alcova/Grey Reef Reservoir, Seminoe Reservoir and Bighorn Canyon National Recreation area. (Wyoming) Trace fossilsPterosaur tracksTatenectes T. laramiensis Redwater Shale MemberA cryptoclidid plesiosaurPantosaurus P. striatus Redwater Shale MemberA cryptoclidid plesiosaurMegalneusaurus M. rex Redwater Shale MemberA thalassophonean pliosaurBaptanodon B. natans Redwater Shale MemberAn ophthalmosaurid ichthyosaurPlesiosaurus "P." shirleyensisMaterial now lost.W. R. O'Keete, F. R. and Wahl Current taxonomic status of the plesiosaur Pantosaurus striatus from the Upper Jurassic Sundance Formation, Wyoming, article on pages 37-47 of the complete issue, 2003, Paludicola, 4 (2) : 27-68. Paperback – January 1, 2003Possibly a junior synonym of Pantosaurus striatus
Fish Genus Species Member Material NotesOccithrissops O. willsoniAn ichthyodectiformCaturus C. dartoniA caturid amiiformHybodontiformes indeterminate Redwater Shale MemberTeethBelongs to a group of shark like cartilaginous fish called the Hybodontiformes. This might either be Hybodus or Asteracanthus. Found in association with Tatenectes.
Invertebrates Genus Species Member Material NotesPachyteuthis P. densusA belemniteWyoteuthis W. linsterorumA belemnite
References