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Late Cretaceous and Cenozoic Mammals of North America: Biostratigraphy and Geochronology. Michael O. Woodburne, ed. 2004. Columbia University Press, New York, 391 + xv p. $95.00. ISBN 0-231-13040-6.
Fossil mammals were first collected by trappers, soldiers, and natural history surveys from the American West in the mid-nineteenth century. These initial discoveries led to subsequent fossil collecting expeditions by many prominent North American vertebrate paleontologists of the day (Lanhan, 1973). As a result of these discoveries, for the past 150 years paleontologists working in continental deposits of North America have used the extensive sequence of fossil mammals, particularly from the west, to calibrate geological time and understand faunal evolution. Late Cretaceous and Cenozoic Mammals of North America synthesizes our current knowledge of land-mammal localities, faunas, and biochronology on the continent extending back 100 million years.
Following the recommendation of the 1937 Vertebrate Section of the Paleontology Society (predecessor to the Society of Vertebrate Paleontology, SVP), development of the continental land-mammal age nomenclature and chronology led to the "Wood Committee Report," which attempted to formalize North American land-mammal ages, or "NALMAs" (Wood et al., 1941). Although this report focused on the Tertiary, important late Cretaceous and Pleistocene mammal localities were also included. The NALMAs are based on several principles, including: 1) each landmammal age is defined by four different biochronological indicators, i.e., index fossils (unique to age), first and last appearances, and characteristic fossils (the latter not necessarily restricted to the age); 2) each is a temporally unique biochron, i.e., it does not overlap in time with the next younger, or older, age; 3) each land-mammal age is about the same duration as the others; 4) no ages were proposed to straddle Cenozoic epoch boundaries; and 5) taken together, the NALMAs span all of the Cenozoic.
With the discovery of new fossils and the advent of radioisotopic and paleomagnetic dating techniques during the second half of the twentieth century, the NAMLAs were open to scrutiny and further refinement. Particularly noteworthy in this regard were the revised calibrations of the NALMAs using K-Ar (Evernden et al, 1964) and magnetostratigraphic dating methods (summarized in Opdyke and Channell, 1996). Realizing the need for integration of these new data sets, the members of the SVP held a symposium in Dallas in...