The Upper Cretaceous Two Medicine Formation of northwestern Montana has promise of yielding the most comprehensive data ever documented concerning the evolution of Upper Cretaceous dinosaur faunas and their respective ecosystems. Preliminary collection of dinosaur specimens from various stratigraphic positions throughout the 650 meter thick (12 million years) unit has produced primitive, opportunistic species (ancestral to known lineages) from basal sediments; conservative species from "upland" sediments; and transitional (Judithian to Edmontonian) species from uppermost sediments. In each case a regressional or transgressional phase of interior seaway fluctuation can be correlated with a particular fauna. The objective of this proposal is to collect additional specimens and data from previously known and new, uncollected sites for use in subjecting previous hypotheses, concerning physical, causal effects of speciation, to rigorous tests. Additionally, the Two Medicine sites offer considerable promise of yielding a substantial amount of new data pertaining to ancestral and descendant Upper Cretaceous dinosaur species. Determination of transitional variables is made possible, owing to the fact that abundant, well preserved specimens of numerous ontogenetic stages are available. The proposed time frame for the project is three years.
