Wyoming and neighboring states have a long tradition of important fossil dinosaur discoveries that continues to this day. Recent finds in the Elk Basin, near Cody, Wyoming, by paleontologist Dr. Marilyn Wegweiser (Georgia College and State University) represent a new and apparently very productive Late Cretaceous site. The site will be the focus of Earthwatch volunteers starting this summer.

Wegweiser, principal investigator of Wyoming's Mystery Dinosaur, presented her preliminary finds as an invited speaker at the Tate Conference at the Paleontology Museum at Casper College, Wyoming, on June 8. In a lecture titled "Sequence Stratigraphy and Paleoecology of Late Cretaceous Campanian-Maastrichtian Transition Strata in the Western Bighorn Basin Region," Wegweiser reported on her first two seasons of excavation at the site.

"There is a paucity of published research in the literature about this area and its rocks," said Wegweiser. "There are dinosaurs here in rocks that, in part because this area is largely unmapped and not explored geologically, have never yielded dinosaurs before. In the last two summers I found 29 paleontological resource sites in Elk Basin, constrained to four stratigraphic intervals. They were just waiting to be discovered."

Wegweiser also reports finding dinosaur tracks occurring in the same layer as dinosaur fossils to be excavated this summer. These are among the first dinosaur footprints to be discovered in association with dinosaur bones, a tremendous boon for exploring the behavior of these prehistoric reptiles.

Although it is too early to accurately identify the fossils, Wegweiser has found at least one potentially new large bipedal dinosaur, the primary focus of Earthwatch teams this summer. So far about six meters of it has been exposed, and that is just the femurs and a few ribs.

"Being that big and bipedal in the Late Cretaceous strongly suggests a meat eater of some kind," said Wegweiser, although she admits it could also be a hadrosaur, or duck-billed dinosaur. "With some of the other fossils associated with it, it could be an entirely new animal."

Perhaps not as stirring as the discovery of a potentially new dinosaur, but of great importance, Wegweiser found vital clues to the paleoecology of the region. Her preliminary findings suggest that the area was near the western shoreline of a great interior sea during the Late Cretaceous, and was subject to repeated flooding from approximately 70 million to 66.5 million years ago.

"Sedimentological studies point to an active salt marsh system, a place with lagoons and mud flats influenced by diurnal tides," said Wegweiser. "These modern environments are wonderful ecological habitats with an amazing amount of biodiversity. Understanding the Cretaceous salt marsh will teach us a great deal about near shore life then."

Wegweiser will also be presenting her findings at the Society of Vertebrate Paleontology meeting in Oklahoma this October, at which point she may have more definitive results from her exciting finds. In the mean time, Earthwatch teams will be eagerly unearthing Wyoming's Mystery Dinosaur in an effort to better understand the paleoecology of Elk Basin.

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