| Evaluation of a large collection of Tertiary decapod crustaceans, collected from the Pacific Northwest of North America, has resulted in a major advance in knowledge of the systematics, paleobiogeography, and evolution of the decapod Crustacea, especially the Brachyura. Nineteen of approximately sixty brachyuran families as currently defined by biologists were studied. Eighteen new species, seven new genera, forty-seven new combinations, and two nomina nova are recognized in this work. One subfamily was raised to family status, several subgenera were raised to generic level, and several species were synonymized. The definitions of eleven families were extensively revised, and the geologic range of numerous families and genera were extended, resulting in major revisions in our understanding of the evolutionary history of these animals. Further, most families discussed herein were evaluated in the context of modern biological studies as part of a major effort to modernize decapod paleontology.; The brachyuran decapods demonstrate distinctive paleobiogeographical patterns during the Cretaceous and Tertiary, and these patterns are consistent with those documented globally. The decapod fauna is composed of five major components: (1) a North Pacific component, (2) a North Polar component, (3) a component of Tethyan origin, (4) an amphitropical component, and (5) a component derived from the high southern latitudes.; The Cretaceous and Tertiary faunas of the North Pacific Ocean were initially dominated by taxa, of North Pacific origin. Diversity was highest in the Pacific Northwest of North America during the Eocene, and has declined steadily since then. Diversity in Japan was relatively low until the Miocene, when diversity increased markedly due to the tropical influence of the Tethys and Indo-Pacific region. Diversity has remained high in Japan. The Cretaceous, Eocene, and Miocene were times of evolutionary expansions within the Brachyura and were separated by periods of evolutionary stasis. |
