Gradual dinosaur extinction and simultaneous ungulate radiation in the Hell Creek Formation.

Title	Gradual dinosaur extinction and simultaneous ungulate radiation in the Hell Creek Formation.
Authors	Robert E. Sloan, J. Keith Rigby, Leigh M. Van Valen and Diane Gabriel
Magazine	Science
Date	05/02/1986
DOI	10.1126/science.232.4750.629
Introduction	Research indicates that dinosaur populations in Montana, Alberta, and Wyoming experienced a progressive decline, commencing 7 million years prior to the close of the Cretaceous period. This decline intensified significantly in the final 0.3 million years, coinciding with increased ecological pressure from swiftly adapting ungulates. During this period, a noticeable decrease in both dinosaur diversity and population density was observed. The most recent dinosaur remains are situated within a geological channel that also preserves Mantuan mammal teeth, seven distinct dinosaur species, and Paleocene pollen. The apex of this channel lies 1.3 metres above the estimated location of the iridium anomaly, which marks the Cretaceous/Tertiary boundary.
Quote	Robert E. Sloan, J. Keith Rigby and Leigh M. Van Valen et al. Gradual Dinosaur Extinction and Simultaneous Ungulate Radiation in the Hell Creek Formation. Science. 1986. Vol. 232(4750):629-633. DOI: 10.1126/science.232.4750.629
Element	Iridium (Ir)
Industry	Research & Laboratory

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