MESOZOIC MARINE REPTILE DISPARITY


557


FIGURE 4. Mesozoic marine reptile disparity and time-bin sample size. Disparity through time is based on the data in Figure 3A,B, showing the mean sum of variances (solid black line) and sum of ranges (dashed black line) results. Bin sample size is plotted in the same 16 Mesozoic time intervals (solid red line).


TABLE 3. Statistical tests for significant differences/shifts in functional disparity and functional morphospace occupation between successive Mesozoic time bins. For comparative purposes, statistical tests for a disparity shift between the Carnian and Hettangian–Sinemurian are also provided. Disparity tests are based on paired-sample t-tests and likelihood ratios (LR). Functional morphospace occupation tests are based on nonparametric multivariate analysis of variance (NPMANOVA), performed on PC scores from the first 11 PC axes. Uncorrected and Bonferroni-corrected p-values are reported. Bold values represent statistically significant results where p-values are <0.05 and LRs are >8. See text in the “Stratigraphic Binning” section for full time-bin names and age ranges.


Paired-sample t-tests


Time-bin comparison Ole/Ani


Ani/Lad Lad/Car Car/Nor


Nor/Het-Sin *Car/Het-Sin


Het-Sin/Plei-Toa Plei-Toa/Aal-Bath Aal-Bath/Cal-Oxf Cal-Oxf/Kim-Tith Kim-Tith/Ber-Bar Ber-Bar/Apt-Alb Apt-Alb/Cen-Tur Cen-Tur/Con-San Con-San/Camp Camp/Maas


0.520 0.232 0.631 0.023 0.011 0.058 0.489 0.396 0.100 0.153 0.072 0.834 0.018 0.404 0.361


1 1 1 1


Marginal likelihoods


p-value Corrected p-value Likelihood ratios (LR) 0.443


0.373 0.177 0.926 1 1 1 1 1 1


0.286 1 1


extinctions throughout the Late Triassic. When examining disparity in terms of the sum of variances metric (Fig. 3A), the overlapping confidence intervals associated with the Norian and Hettangian–Sinemurian bins suggest a nonsignificant disparity decline during the Triassic/Jurassic transition. This most likely arises from inflated confidence intervals because of a low sample size in theNorian (n=5).When this successive bin comparison is examined using variance-based statistics (Table 3), there is evidence for a statistically significant


1.295 1.102 1.861 1.003 8.268


0.982 0.168 0.304 0.001


12.751 2.273


13.592 1.085 2.971 1.071 1.197


0.959 0.493 0.569 0.242 0.899 0.337 0.043 0.058 0.922 0.278


NPMANOVA


p-value Corrected p-value 0.126


1 1 1 1


10.374 —— 2.228 1.025 1.125


1 1 1 1 1 1 1 1 1


decline, according to marginal likelihoods (LR: 8.27, exceeding threshold for significance; Royall 1997) and standard statistical tests (paired-sample t-tests, p=0.023; note this is not robust to correction for multiple comparisons). The sum of ranges metric (Fig. 3B) shows a statistically significant decline between and the Carnian and Norian bins, but there is no decline in disparity between the Norian and the Hettangian–Sinemurian bin of the earliest Jurassic, so conflicting with the results for the sum of variances. In this primary analysis, the


0.108 1


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