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The Late Devonian Mass Extinction: the Frasnian/Famennian Crisis. George R. McGhee, Jr. xiii + 303 pp. Columbia University Press, 1996. $29 paper.
Five major mass extinctions stand out in plots of the number of families (or genera) through Phanerozoic time (the past 550 million years). These crisis intervals occur rapidly and are marked by substantial drops in global biodiversity and broad taxonomic impact. The temporal and geographical patterns of extinction, potential causes, and evolutionary consequences are topics of considerable interest. Several recent books on the end-Cretaceous episode (the smallest of the five) continue the debates about the disappearance of the dinosaurs and the effects of an asteroid impact 65 million years ago. The end-Permian mass extinction (the most severe in the history of life) and its dramatic impact are considered in an earlier volume of Columbia University Press's Critical Moments in Paleobiology series. Now George McGhee has provided an excellent synthesis of one of the less widely known of the "big five" crises: that of the Late Devonian.
About 365 million years ago, 22 percent of all families of marine animals (57 percent of the genera, and at least 75 percent of the species) disappeared between the two stages of the Late Devonian, the Frasnian (pronounced Franian) and Famennian. The recently evolved terrestrial plants and vertebrates also suffered significant extinctions. In 1969, Canadian paleontologist Digby McLaren suggested that an asteroid impact was the prime cause of this faunal turnover and destruction of ecosystems. McGhee supports the argument that extraterrestrial objects played...