User:Abyssal/Ornithomimipus

Ornithomimipus is an ichnogenus of dinosaur footprint. In 2001, McCrea and Sarjeant used the ratio of an Ornithomimipus print's length to its width in order to help identify what kind of animal produced it. Previous workers lead by Moratalla have used this method to distinguish tracks left by ornithopods and theropods. Gypsichnites had an average length-to-width ratio of 1.09 among twelve prints examined by McCrea and Sargent at the W3 Main tracksite. Their results excluded ornithopods from candidate trackmakers because the length-to-width ratios of their tracks were at least 1.25.

W3 Main
Ornithomimipus is known from a fossil site called the W3 Main track site. This site forms part of a footwall in the Smoky River Coal Mine near Grande Cache, Alberta. The fossil footprints at W3 Main were first reported in the early 1990s. These reports were examined by several follow-up expeditions during the summer of 1998. McCrea and Sargent describe W3 Main as difficult to study because the tracksite is at about 1700 meters of altitude and frequently obscured by adverse weather conditions like fog or overcast skies. Compounding the problem, the footwall itself is oriented in such a way that the sun only shines on it for part of the day. Ornithomimipus occurs alongside other theropod tracks like Aquatilavipes curriei, Irenesauripus, Gypsichnites, and Irenichnites. Ankylosaur tracks of the ichnogenus Tetrapodosaurus are also present. McCrea and Sargent have called this association of different dinosaur trackmakers as "a rich late Early Cretaceous fauna." These tracks are preserved in rippled sandstone in the presence of many trace fossils left by both large and small invertebrates. Plant fossils preserved in the same stratigraphic unit as the tracks, the Gates Formation, include ferns, conifers, cycads, ginkgoes, and two species of flowering plant. Larger plant remains include fossil logs and tree stumps that are spaced far apart from one another. The fossils of W3 Main paint a picture of an ancient coastal plain or delta. The lack of mud cracks in the track bearing sediments is evidence that they were never dehydrated fully before preservation, possibly because the tracks were left in water a few centimeters deep or just because the exposed sediment was very wet when stepped on.

Reference

 * McCrea, Richard T. 2001. Tourism Opportunity Analysis: Dinosaur Tracks In the Grande Cache Area Tourism opportunity analysis dinosaur tracks in the Grande Cache area. Publisher: Edmonton : Alberta Economic Development. ISBN 0778512622.
 * McCrea, R. T. and W. A S. Sarjeant. 2001. New ichnotaxa of bird and mammal footprints from the Lower Cretaceous (Albian) Gates Formation of Alberta; pp. 453–478 in D. H. Tanke, and K. Carpenter, (eds.), Mesozoic Vertebrate Life. Indiana University Press, Bloomington and Indianapolis.

Hook
... that fossil dinosaur footprints called Irenichnites have been discovered in an Alberta coal mine?