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J. David Archibald Department of Biology, San Diego State University, San Diego,
 

Summary: e74
J. David Archibald
Department of Biology, San Diego State University, San Diego,
California 92182-4614, USA
The recent article by Fastovsky et al. (2004) examines the Mesozoic
record of dinosaur diversity. For this study they utilized recently published
dinosaur distribution data complied by Weishampel et al. (2004). A major
concern of Fastovsky et al. (2004) was the dinosaur record during the clos-
ing 10 m.y. of the Cretaceous. It is this aspect of their paper on which I
am commenting.
The authors conclude: "The database does not support the claim that
dinosaur richness was decreasing toward extinction during the ~10 m.y.
preceding the Cretaceous-Tertiary boundary" (p. 880). Note that the authors
qualified this statement with the phrase "decreasing toward extinction." This
is a subjective opinion separate of the more objective issue of whether there
was such a decline. When read carefully it is quite clear that their own data
show a decline. For example note their absolute richness for this interval in
Table 5 with a decline of 51 genera from late Campanian to 41 genera in the
late Maastrichtian. Note a similar pattern for the left hand bars in Figure 5.
The authors do not accept these results but rather introduce what they

  

Source: Archibald, J. David - Department of Biology, San Diego State University

 

Collections: Biology and Medicine; Geosciences