Wannagan Creek site

The Wannagan Creek site is a fossil site found in the South Unit of Theodore Roosevelt National Park of North Dakota, USA. The site is Paleocene in age, approximately 60 million years old. Paleontologists of the Science Museum of Minnesota have studied the site for nearly thirty years. The site is thought to represent a paleoenviroment of subtropical swampy lowland and forests. Preservation is excellent for both the flora and fauna of the site. Trace fossils of crocodilians and other vertebrates have also been discovered.

Topography/Geology

The topography of the site is that of a badland, due to the downcutting of the Little Missouri River. The rock units are likely sediments derived from the Laramide orogeny deposited in an ecosystem dominated by rivers, streams, ponds, lakes, and swamps.

The Wannagan Site is found in the upper portion of Bullion Creek Formation. This geologic formation is exposed only in the South Unit of Theodore Roosevelt National Park. The Bullion Creek is a heterolithic unit consisting of yellow to tan, poorly lithified claystones, mudstones, and siltstones with a lesser amounts of interbedded fine-grained sandstones and lignite. The Bullion Creek Formation reaches a thickness of over 60 m. Wannagan Creek site is overlain by the Sentinel Butte Formation. This formation is generally gray to brown in color but is similar in lithology to the Bullion Creek. The Sentinel Butte is roughly 90 m thick. The contact between the two formations is roughly 6 m above the Wannagan site. The Sentinel Butte contains an extensive stump-bearing petrified wood bed above the contact at the site.

Fauna

Many mammals are found at the site. All are small compared to modern mammals, the largest being sheep-sized. Preserved mammals include a squirrel-like primitive primate and "Ptilodus"; an arboreal multituberculate. The largest mammal at the site is the condylarth herbivore "Phenacodus". An additional mammal fossil is "Protictis", a weasel sized member of Viverridae that may have hunted on the forest floor.

Reptiles are the dominant animal type preserved at Wannagan. The largest animal (~4 meters [13 ft] in length) found at the site is the eusuchian crocodilian "Borealosuchus formidabilis" (formerly known as "Leidyosuchus formidabilis"). "B. formidabilis" is also thought to be the apex predator of the fauna. The second largest reptile is the champsosaur "Champsosaurus gigas". "C. gigas" is unusual among Paleocene reptiles in that it is larger than its known Mesozoic ancestors; 3 meters (10 ft) in length versus 1.5 meters (4.5 ft) for the largest Cretaceous champsosaurs. Reptiles as a whole decreased in size after the Cretaceous–Tertiary extinction event. Other reptiles include soft-shelled turtles, varanid lizards, a small alligatorid called "Wannaganosuchus", palaeophid snakes, and the snapping turtle-like "Protochelydra zangerli".

Birds from Wannagan include an ibis, an unnamed water bird, and a plover-like shore bird. The two types amphibians found at Wannagan are the giant salamander "Piceorpeton willwoodense" and frogs. Fish include fossil "Esox", freshwater rays, gar, and bowfin. Additionally, the dragonfly "Gomphaeschna schrankii" and the mayfly "Ephemeropteran" have been found.

Flora

The flora of Wannagan is quite well preserved in some cases, with evidence of insect feeding found on many fossils. Most of the fossils have modern equivalents. The list of trees at Wannagan Creek include palms, ginkgo trees, bald cypress, dogwoods, oaks, elms, fig trees, magnolias, dawn redwoods, hackberries, sassafras, sycamores, cherries, mulberries. and cycads. Additional plants found at the site are grape vines, lotus, bur-reeds, cattails, and water-plantago.

ee also

* List of fossil sites "(with link directory)"

External links

* [http://www.state.nd.us/ndgs/NDNotes/ndn9_h.htm North Dakota Geological Survey] Paleontology of Theodore Roosevelt National Park
* [http://www.crocsrule.org/home.html Science Museum of Minnesota] Science Museum of Minnesota's Wannagan website
* [http://www.nps.gov/thro/tr_dinos.htm The National Park Service] Theodore Roosevelt National Park's Paleontology
* [http://paleodb.org/cgi-bin/bridge.pl?action=displayCollectionDetails&collection_no=15000 Paleobiology Database: Wannagan Creek Quarry: Tiffanian, North Dakota]
* [http://paleodb.org/cgi-bin/bridge.pl?action=displayCollectionDetails&collection_no=27640 Paleobiology Database: One Mile North of Wannagan Creek Quarry: Late/Upper Paleocene, North Dakota]