PARAREPTILE COMPLETENESS
more or less linear relationship. On the con- trary, the scatter in CCMb versus SCM is too substantial to support a close relationship. These visual inferences are supported by Lin’s concordance correlation coefficient. Results show a stronger agreement between CCMa and CCMb (ρc=0.704), and between CCMa and SCM (ρc=0.638), than between CCMband SCM (ρc=0.363). Completeness within Parareptile Clades.—From
the histogram of the mean completeness by clade (Fig. 6), it appears that theCCMb is always higher than the two other metrics, except in mesosaurids (which lack a CCMb value, as they are always included in the phylogenies as a family) and the nycteroleteroids. However, the fact that the CCMb values are above the others is not sustained by the statistical tests (Table 3). In lanthanosuchoids, the highest value is the CCMb, but there is only a significant difference between the CCMa and the SCM (U=31, p=0.041). For mesosaurids, there is no significant difference between the CCMa and the SCM. For millerosaurians and nycteroleteroids, there is no significant difference between any of the three metrics. In pareiasaurs, both CCMs strongly differ from the SCM. Procolophonoids are marked by a very significant difference between the CCMb and the SCM, but there is no difference between the CCMa and the SCM. Finally, mesosaurids have the highest completeness values in allmetrics. Completeness within Clades through Time.—The
temporal variation in completeness for each individual clade is shown in Figure 5. Parareptile completeness in the Triassic is only driven by procolophonoids, the only parareptile clade to survive the end-Permianmass extinction. Most notably, and in contrast to the overall pattern when considering all parareptiles, procolophonoid completeness drops in all three metrics across the Permian/Triassic boundary but only reaches an overall minimum in the Middle Triassic. While the different metrics do notgiveexactly thesameresults,theydo show similar patterns within each clade. For example, lanthanosuchoids show an increasing completeness from the Artinskian to the Kungurian, decreasing in the Roadian to a
trough lower than in the Artinskian, and finally increasing again in the Wordian, but
689
with substantially different levels in each metric. The completeness of pareiasaurs consistently decreases between the Capitanian and the Wuchiapingian, then reaches a plateau, slightly increasing (CCMa and CCMb) or decreasing (SCM) in the Changhsingian. In millerosaurians, the Changhsingian completeness value is higher than the Capitanian for allmetrics (theyare only present in these two time bins).
Discussion Parareptile Completeness.—Figure 3 shows that
the completeness of parareptiles through time is consistently high. None of the completeness curves show any great excursions from the mean value. In addition, the minor peaks and troughs that are visible do not correspond to any high or low values of taxic diversity (Fig. 3D). The correlation tests find no significant correlation between generic diversity and any of the three metrics (Table 2). This shows two things. First, thereisnoevidenceofa Lagerstätten effect in parareptiles. If a parareptile-bearing deposit was exceptionally rich and complete, therewould be a temporally coincident peak in both completeness and diversity. As maximum values of complete- ness are not linkedto high taxic richness here, this is not the case. Second, low completeness values not being associated with peaks of diversity suggests that most parareptile genera are not defined based on fragmentary material. Therefore, the likelihood of great synonymy issues is quite low. This interpretation is re- inforced by the mean completeness of parareptiles through time (45% for the SCM, 59% for the CCMa, 63% for the CCMb) being consistently high compared with those measured in other tetrapod clades, namely sauropodomorph dinosaurs (37–40%, Mannion and Upchurch 2010), Mesozoic birds (37%, Brocklehurst et al. 2012), and pelycosaur-grade synapsids (35–40%, Brocklehurst and Fröbisch 2014), whereas fossil specimens of anomodonts were found to be very complete (74%, Walther and Fröbisch 2013, 2014). Regarding correlation between the three
metrics, results differ depending on whether time stages with monogeneric diversity are included or not (Table 2). The main differences
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