The main reason we do not have any dinosaur fossils at the Western Center is because there were none found in this area. The Western Center focuses on the paleontology of the surrounding Riverside County region, which has had very little in the way of dinosaur finds.
The landscape during the time of the dinosaurs was much different than it is today. The area that is now Riverside County was completely underwater during the time of the dinosaurs, which paleontologists call the Mesozoic Era (made up of the Triassic, Jurassic and Cretaceous Periods). This alone makes dinosaur fossils a very rare occurrence in Southern California. It wasn’t until much later, during the Ice Age, that our region was above the water and able to be inhabited by many of the animals we see in the museum today.
(Image: California during the Jurassic Period. Aerial image courtesy of Department of Geology, Arizona State University)