Paleontology in Washington encompasses paleontological research occurring within or conducted by people from the U.S. state of Washington. Washington has a rich fossil record spanning almost the entire geologic column. Its fossil record shows an unusually great diversity of preservational types including carbonization, petrifaction, permineralization, molds, and cast.[1] Early Paleozoic Washington would come to be home to creatures like archaeocyathids, brachiopods, bryozoans, cephalopods, corals, and trilobites. While some Mesozoic fossils are known, few dinosaur remains have been found in the state. Only about two-thirds of the state's land mass had come together by the time the Mesozoic ended. In the Cenozoic the state's sea began to withdraw towards the west, while local terrestrial environments were home to a rich variety of trees and insects. Vertebrates would come to include the horse Hipparion, bison, camels, caribou, oreodonts. Later, during the Ice Age, the northern third of the state was covered in glaciers while creatures like bison, caribou, woolly mammoths, mastodons, and rhinoceros roamed elsewhere in the state. The Pleistocene Columbian Mammoth, Mammuthus columbi is the Washington state fossil.