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Journal of Paleontology 91(5):919–932
Table 5. Eigenvalues with confidence intervals at 95% and correlation coefficients for each variable with the two first components of the PCA obtained with ratio variables (Fig. 3.3). Abbreviations of variables according to Figure 1 and Table 1. Asterisks indicate significant correlation.
Eigenvalue
Lgl/LC LPL/Lgl
Variable LOR/Lgl
Lgl/WglB LOR/WOR WPF/WOR WIG/WglE LPF/LOR LPF/LPA
PC1
–0.0454 –0.1325 0.0321 0.0198
Lower limit –0.1134
–0.0436 0.4429 0.3397 0.8060 0.1328
–0.1942 –0.0323 –0.0141 –0.1030 0.2176 0.1626 0.3712 0.0554
Upper limit 0.0306
–0.0630 0.0946 0.0526 0.0260 0.6396 0.4951 1.1832 0.1995
PC2
–0.4423 0.0775
–0.3170 0.0398
–0.0490
Lower limit –0.7301
–0.4988 –0.1841 –0.5578 0.3163
–0.0185 –0.7759 –0.0859 –0.8082 –0.4093 –0.9295 0.0516
–0.1751
Upper limit –0.0463
–0.0687 0.1015
0.1555 0.1913 0.1596
–0.0573 0.5116 0.1008
PC1
–0.1886 –0.8456* 0.1004 0.1421
–0.1767
0.9140* 0.7712* 0.9797* 0.6453*
Correlation PC2
–0.2019 0.4052
0.7504* –0.1165
–0.1569 0.0972
0.8254* 0.1558 0.5169
In both cases the two groups show significant differences and the discriminant functions were equally efficient in classifying the specimens. The total error from the cross-classification table is 3.53% with both datasets (GMD and RD). To avoid redundancy, only the values of the discriminant function obtained with GMD are shown: centroid values are –3.08 and 1.51 for Bienvillia and Parabolinella, respectively, and the discriminant scores for the holotype and paratype of P.? triarthroides are 1.287 and –0.793, respectively, suggesting that they should be classified as Parabolinella.
The discriminant analysis results were quite similar.
Cladistic analysis.—Revision of the type material of P.? triarthroides reveals that this species has a bifurcate pre- occipital (S1). Thus the original matrix from Monti and Con- falonieri (2013) was accordingly modified for this qualitative character (Ch. 22, state 1 instead of 0 for P.? triarhroides, see Table 2 and Supplementary dataset 5). The analyses performed including all 40 characters (Table 2, Supplementary dataset 5) and with the two treatments of continuous characters (ratios vs. geometric mean) show similar results. In both cases, the species of Parabolinella constitute a monophyletic group, even with different conditions of analysis (without implied weighting and with different function of k), and P.? triarthroides is always recovered within this group. Among all the trees recovered with these different conditions, only those with highest similitude index (similarity=0.95; Supplementary dataset 6.1) are shown: the topology in Figure 5 (CPR + DP matrix), which was obtained applying either maximum parsimony or implied weighting (k=11–14), and the topology in Figure 6 (CPGM + DP matrix), which was obtained applying implied weighting (k=10–14). When the analysis was performed only with the continuous partition, Parabolinella was never recovered as a monophyletic clade (Fig. 7). When the CPR matrix was used, two very similar trees were recovered (similarity=0.9), inde- pendently of the conditions of analysis (i.e., without implied weighting and with different functions of k); and when the CPGM matrix was used, three slightly different topologies were obtained (similarity=0.6, 0.65, and 0.8). For comparison purposes, only the topologies obtained with k=11 are reported for each kind of partition (Fig. 7). The comparison of topologies through unweighted SPR distances obtained from CPR vs. CPGM matrices indicates that they are very different (similarity=0.3–0.55, Supplementary dataset 6.3). Further- more, the consensus tree displays only from two to five shared
internal nodes, out of a total of 20 (Supplementary dataset 6.5). The topologies obtained with the discrete partition are very different to those obtained with CPR and CPGM (the maximum of similarity is 0.35 for CPR, Supplementary dataset 6.5) (Fig. 7). The topologies obtained from CPR are slightly more consistent with the discrete partition than those obtained from CPGM (mean of similarity 0.2755 and 0.1196 for each strategy, respectively, see Supplementary dataset 6.5). Finally the tree obtained from the complete matrix, but using CPGM, shows slightly higher support values than including CPR (Figs. 5 and 6). When all characters are included in the analysis, the
discrete partition controls the structure of the tree (Figs. 5–7). The topologies obtained for each complete matrix (with CPR or CPGM data) do not differ so widely with the use of different k
values.As mentioned above, when the analyses were performed with the complete dataset, the genus Parabolinella was always recovered as a monophyletic group and the differences are within the Parabolinella clade (Figs. 5, 6). The Parabolinella clade is supported by four synapomor-
phies within the discrete partition: the presence of an adaxially bifurcated S1 furrow (Ch. 22, 0→1), which is the only non-homoplastic character; the palpebral lobes centered to S2 (Ch. 17, 0→1); the anterior termination of glabella rounded (Ch. 20, 0→1); and the S2 furrows shorter than S1 (Ch. 25, 0→1) (Figs. 5, 6; Table 2). Within the continuous partition, four additional synapomorphies emerge with CPR and with CPGM, although they are not the same. Considering CPR, the synapomorphic transformations are: shorter glabella related to the length of the cephalon (Ch. 1, 0.68→0.63); the preglabellar field occupies a larger proportion of the preglabellar area (sag.) (Ch. 3, 0.69→0.72); preglabellar field well developed related to length of the occipital ring (sag.) (Ch. 4, 0.58→0.94); posterior cephalic border shorter as a proportion of length of occipital ring (Ch. 6, 0.58–0.59→0.54–0.57) (Fig. 5). The first three of these synapomorphies also are recovered as characters of importance to distinguish the two genera in the morphometric analysis. On the other hand, the synapomorphies of the genus for CPGM are: a well-developed preglabellar area (sag.) and preglabellar field (sag.) (Ch. 3, 0.51→0.69-0.73; Ch. 4, 0.35→0.48–0.55); and a short (sag.) glabella with a narrow base (tr.) (Ch. 1, 1.97→1.92; Ch. 7, 2.1– 2.18→2.06) (Fig. 6). In this case, all four synapomorphies found coincide with variables that allow separation of both genera in the morphometric analysis.
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