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ANTOINE VERRIÈRE ET AL.
when monogeneric bins are not included is a significant correlation appearing between CCMa and CCMb for Spearman’s ρ (ρ=0.564, p=0.046). It could also mean that these five bins were extreme values, whose impact is exaggerated by the fact that they represent only one genus. By excluding them, less dis- torted information is measured in the correla- tion test. The results of Lin’s concordance correlation coefficient (Fig. 4), which does not depend on the time series, support the corre- lations found by the tests when monogeneric time bins are excluded. The two character completeness curves
TABLE 4. Average percentages of completeness attributed tomain portions of the skeleton for the CCMa and the SCM.
Portion of the skeleton Skull
Mandible Dentition
Axial skeleton Shoulder girdle Forelimbs
Pelvic girdle Hind limbs Osteoderms
CCMa 52.3%
5.7% 6.8% 7.1% 4.6% 8.2% 4.3% 8.2% 2.8%
SCM
28.3% 4.4% 0.2%
35.6% 5.8% 7.5% 8.0%
10.2% 0.0%
(Fig. 3A,B) are significantly and strongly cor- related (Table 2) and have a strong agreement (ρc=0.704). This shows that, despite different protocols, the two methods measure the same signal. In contrast, only the CCMa is significantly correlated with the SCM, with a strong agreement (ρc=0.638), whereas none of the statistical tests indicates a significant relationship between the SCM and the CCMb (Table 2), and the agreement is low (ρc =0.363), despite the strong correlation between the lat- ter and the CCMa. This could be due to the fact that the phylogenetic character matrices used to calculate the CCMb include many matrices intended to examine a specific clade, while matrices examining a broader range of taxa form the character list used in the CCMa. In a clade-specific phylogenetic matrix, the nature and the number of characters is implemented from the amount of available material in the group, so there already is a sorting of the studied elements, possibly leading to higher estimations of the group’s CCMb value. Although the CCMa and the SCM both weigh each portion of the skeleton differently (Table 4), the difference between them is dam- pened by several factors. First, the combined matrix used in the CCMa was constructed to attribute a percentage of completeness to each bone; every skeletal element is therefore represented, potentially differing from some of the matrices used for the CCMb. Moreover, both the SCM and the CCMa are implemented from the same list of the bones known for each taxon. Apart from some differences (for the SCM, every single skeletal element is considered, even in bilateral symmetrical
bones, whereas the type of bone is only marked as present or absent for the CCMa), the two metrics are based on the same descriptive data.
Figure 3 shows examples of how some
patterns present in both CCMa and SCM are not found in the CCMb. For example, the Kungurian holds the lowest values of CCMa and the SCM in the Permian, while the curve shows a plateau for the CCMb. This may be driven by the bolosaurians, which have a higher CCMb than SCM and CCMa (Fig. 6). Calculation of the CCMb includes two bolosaurian-focused matrices (Müller et al. 2008; Falconnet 2012) in addition to the general matrices on parareptiles. In these matrices, the bolosaurian genera are scored for almost all characters, as the matrices are mostly based on cranial characters visible in the majority of bolosaurians, even though the number of skeletal elements preserved in these taxa is low (indicated by the low SCM score). While these factors explain the correlations between the completeness curves through time, other parameters must be taken into account to understand the completeness values of the individual parareptile clades (Fig. 6). As described above, the CCMb always holds the highest values, except in nycteroleteroids and mesosaurids (for which the CCMb could not be calculated), but once again, this is not always significant according to the statistical tests (Table 3). Furthermore, the relationships between the three metrics for each clade are not always the same and need to be considered in light of the respective fossil record of each individual group. Bolosaurians, millerosaurians, lanthano- suchoids, and procolophonoids each have a
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