Figure 6. Graphical model for analysis of the time of origin of Mesonychia, assuming that all uncertainty is in the left or origination tail of the confidence interval (compare work sheet in Table 4). Sample space is three-dimensional as in Figure 4. The sample space shown here reflects the exponentially declining availability of older fossil-bearing sedimentary rocks at the earth's surface (F), and diversification of Mesonychia at a constant rate in the d dimension from the time they are first inferred to have existed until they are first found as fossils. Simulation built into the analysis tests analytical assumptions by repeatedly drawing samples of size n = 56 from B + C (or ETD) and counting the number of times all fall in C (or OTD) in 1000 trials (one sample is shown in simulation bar at bottom of figure). All samples drawn from B + C fell in C in 37 of 1000 simulation trials, which is close to the 50/1000 times expected with a critical likelihood l = 0.05.