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This chapter presents a comparative study of the structure and function of chemical senses in aquatic mammals. It first discusses the chemosensory systems of extant species of Monotremata, Didelphimorphia, Insectivora, Carnivora, Sirenia, Cetacia, Artiodactyla, and Rodentia. It then examines the evolution of chemical senses through a comparative analysis of the olfactory organs of semiaquatic mammals and terrestrial mammals.

The order Carnivora has a shorter history in Africa than on any other continent except Australasia and South America. The definite record of the order on the African continent extends back to the Lower Miocene, though some earlier records may exist. During this time, the order has diversified enormously, first as a result of migrations from Eurasia and later as a result of in situ speciation. Despite this, little is known about the history of African Carnivora compared with most continents, mainly due to the geographically biased fossil record on the African continent. For the Plio-Pleistocene, only parts of northern, eastern, and southern Africa have an adequate Carnivoran fossil record, and for the Miocene the situation is much worse, as only some time slices of this epoch have an adequate record in some parts of eastern Africa. This chapter describes the systematic paleontology of Pholidota. It reviews more than 100 genera and about twice that many species. The organization is by family (in standard order) and genus. The chapter concludes with short sections on biogeography and migration patterns.

The mammal fauna of California was significantly shaped by Beringian migrations that occurred episodically from the Eocene through the late Pleistocene. Wide-dispersing mammals show evidence of continental divisions across North America, with western clades retreating variously to the coast or ice-free regions during glaciation periods. For small mammals, deep phylogeographic divergence is common due to vicariant events, and due to their limited dispersal, they often remained isolated. Severe habitat loss and degradation in the past few centuries has decimated many populations that occur in riparian corridors from east to west, further isolating historically contiguous populations and preventing migration. Barriers to dispersal existed in the Monterey Bay region from about 8–2 Ma, because the southern Sierra Nevada drained into the Pacific Ocean from this location and presented a significant obstacle for the dispersal of small mammals. The central Sierra Nevada, southern Sierra Nevada (particularly around the San Joaquin River), the outer Coast Ranges (particularly around the San Francisco Bay south to Monterey), San Bernardino Mountains, Tehachapi Mountains, Peninsular Ranges, and Inyo Valley are identified as focal areas for endemic taxa. A number of studies now verify that divergence for a number of taxa from the warm deserts began in the Miocene east of the Mojave.

This chapter provides a review of the evolutionary and taxonomic history of the Musteloidea, which is the most species-rich superfamily of the Carnivora, containing approximately 30% of the extant species in the order. An up-to-date summary of knowledge on the evolutionary and taxonomic history and phylogenetic relationships of the Mephitidae, Ailuridae, Procyonidae and Mustelidae is provided. Multilocus DNA sequences have made a large impact on the understanding of phylogenetic relationships among the Musteloidea. Molecular data have revealed distinct families (Ailuridae and Mephitidae) within the Musteloidea and have illuminated new relationships based on tempo and patterns of evolution within the Procyonidae. Morphological data in conjunction with molecular data have been used to elucidate species boundaries within certain musteloid genera and have led to the discovery of a new species. Research studies published during the last 30 years have enriched and transformed our understanding of the evolution of musteloid biodiversity.