FIGURE 3. Ecological model for development of low-diversity, high-equitability biofacies in the Late Cenomanian Hartland Shale Member, Greenhorn Formation includes three major components: 1) Recruitment lottery - breeding subpopulations A-E produce high numbers of larva, but successful recruitment is unpredictable. Recruitment is represented by lines with arrows; 2) Growth rate/tolerance - bars representing colonization and growth of recruits (along bottom of diagram) are keyed to subpopulations A-E by fill patterns. Time progresses from left to right in the figure; 3) Disturbance factor - fluctuations of the redox boundary above the sediment-water interface (SWI) represented by red fill. Species richness (S) is represented by a dashed line below the diagram and equitability (e) by a shaded curve. Fluctuations in diversity and equitability are a function of interaction between the three factors described above (based on Sageman and Bina, 1997).