I study freshwater fish evolution in the late Cenozoic of North America. Various fossil salmonids, minnows, suckers, sunfish, and sculpins are important in Miocene, Pliocene, and (to a lesser extent) Pleistocene sediments of Washington, Oregon, Idaho, Utah, Nevada, California, and Arizona, as well as adjoining states and Mexico. When compared to the Recent faunas of Western U.S., these ancient fishes are surprisingly more diverse and more specialized than their recent counterparts, reflecting the destructive effects of Pleistocene climatic fluctuations.
Fish diversity and evolution are a function of stability of aquatic habitat, which depends on consistent volume and temperature of water. Western habitats have never benefited from the stability of aquatic habitats characteristic of Eastern North America because active tectonic plate margins of the west have disrupted, isolated, and elevated habitats causing high rates of extinction.
- Curator Emeritus of Fishes, Museum of Zoology
- Curator Emeritus of Lower Vertebrates, Museum of Paleontology
- Professor Emeritus of Ecology and Evolutionary Biology
- Professor Emeritus of Geological Sciences