The study of dinosaur abundance in the Hell Creek Formation by Sheehan et al. (2000) raises three points that require comment. Additionally, some of their history of the “3 m gap” requires emendation. As the authors correctly state, in the late 1970s and early 1980s various workers observed that dinosaur remains seemed to be absent or rare in the upper 3 m of the Hell Creek Formation in northeastern Montana. As Sheehan et al. note, this was subsequently seen as a geographically wider phenomenon. It must be emphasized that this was first noted before the 1980 publication of the seminal...

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