He has worked with dinosaur remains from the southwest United States of America and Mexico [1][2][3] and has been responsible for discovering new and important genera.
1990 He was an adjunct Professor of Geology at Mesa State College, Grand Junction, Colorado, USA adjunct Associate Professor at University of Utah, Salt Lake City, Utah and a Research Associate of the Denver Museum of Natural History in the Denver Museum of Nature and Science, Colorado Boulevard, Denver, Colorado.
An expert on the Mesozoic, he has spent more than thirty years excavating fossils across the southwestern US and Mexico authoring and coauthoring more than 75 professional papers.
The reconstruction of ancient marine and terrestrial environments, biostratigraphy, paleoecology, and mass extinctions are some of his interests.
His researches in the middle Cretaceous of Utah indicate that the origins of Alaska and the first great Asian-North American faunal interchange occurred about 100 million years ago, which his numerous trips to China and Mongolia have substantiated.