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and skeletal proportions among parareptiles (Fig. 1B) does not allow use of a single model for all taxa. Pareiasaurs, for example, have an entirely different Bauplan when compared with procolophonoids or mesosaurids. Thus, seven models were constructed for seven principal clades with distinct morphological character- istics (Supplemental Table 1). They were based on several specimens from different taxa; the list is detailed in Table 1. For groups with unknown skeletal elements, volumes of these missing parts were calculated based on the proportions found in the most complete and most morphologically similar model. Data Set.—The study was carried out at
the genus level. This choice was motivated by the fact that most parareptile genera are monospecific and most of the phylogenetic analyses were performed at the genus level as well. To include asmany taxa as possible while avoiding synonymy issues, we extracted a list of valid parareptile genera from the latest and most exhaustive study on this group (Ruta et al. 2011).Added to this listwere: Abyssomedon
TABLE 1. List of the specimens used to construct the skeletalmodels used for calculation of the SCM. Quotation marks refer to the name above.
Model Bolosauria Specimens
AMNH 4327 MNG 8852
Lanthanosuchoidea PIN 271/1 PIN 3706/9
Mesosauridae SMNH R212
SAM PK-K 8381
Millerosauria
SAM PK 709 MBR 5605 BPI 3821 RC 14 RC 70
Nycteroleteroidea PIN 2212/92 Pareiasauria
PIN 2212/6 SMNS 58317
Procolophonoidea BP/1/962
SAM PK-K 7711
SAM PK-K 10434
Species
Bolosaurus striatus Eudibamus cursoris
Lanthanosuchus watsoni
Lanthaniscus efremovi
Mesosaurus tenuidens
″ ″
″
Milleretta rubidgei ″ ″
Emeroleter levis
KPM uncat/E1 ″ KPM 232
Deltavjatia rossicus ″ ″
Procolophon trigoniceps
″ ″
BMNH R-3375 ″ BMNH R-518 ″
(MacDougall and Reisz 2014), Contritosaurus (Ivakhnenko 1974), Delorhynchus (Reisz et al. 2014), Erpetonyx (Modesto et al. 2015), Feeserpeton (MacDougall and Reisz 2012), Obirkovia (Bulanov and Yashina 2005), and Phonodus (Modesto et al. 2010). In the end, we considered 76 taxa of parareptiles. Mesosaurids were not included in the CCMb analysis because they were not scored as genera or species in any of the included phylogenetic studies but rather treated as a composite clade coding. A matrix describing precisely which
skeletal elements and how many of them are known for every genus was built. Descriptions of the specimens were extracted from the lit- erature. To investigate completeness patterns through time, knowledge of the stratigraphic range of the genera was assembled. This data was downloaded from the Paleobiology Database (Uhen and Sessa 2013); the data set may be considered complete as of December 2015. Statistical Tests.—CCMand SCMgivea
percentage value for each taxon (Supplementary Table 2). An average completeness was calculated for each Permian and Triassic stage (Fig. 3). The three curves (CCMa, CCMb, and SCM) obtained were comparedwith one another and to a generic diversity curve (Fig. 3D) with nonparametric correlation tests: Spearman’s rank correlation coefficient (Spearman 1904) and Kendall’s tau rank correlation coefficient (Kendall 1938). To correct for autocorrelation, the data were transformed via generalized differencing (McKinney 1990). Table 2A presents results of the tests obtained on the complete data set. To avoidexaggeratedweight given to some taxa due to monogeneric diversity in five stages (Gzhelian, Asselian, Sakmarian, Ladinian, and Rhaetian), we also applied the correlation tests on a data set excluding these stages. Results obtained with this data set are presented in Table 2B. The correlation between metrics was also
analyzed without taking the temporal dimen- sion into account. Figure 4 shows the scatter plots of the three metrics in pairs. To depart from the natural correlation due to the three metrics quantifying the same information, we used Lin’s concordance correlation coefficient
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