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. 2020 Oct 20;8:e10145. doi: 10.7717/peerj.10145

Figure 4. Summary of potential outcomes for the analysis of the data matrix including Tylosaurus kansasensis and Tylosaurus nepaeolicus.

Figure 4

Hypothetical T. nepaeolicus specimens are represented by black skulls and hypothetical T. kansasensis specimens are represented by gray skulls. (A) If the current hypothesis is supported and T. kansasensis are juveniles of T. nepaeolicus (Jiménez-Huidobro, Simões & Caldwell, 2016), most or all T. kansasensis specimens will be recovered as less mature than most or all T. nepaeolicus specimens. (B) If T. kansasensis are juveniles of T. nepaeolicus, and the taxon is sexually dimorphic, most or all T. kansasensis specimens will be recovered as less mature than most or all T. nepaeolicus specimens and before the onset of sexual maturity (represented by a bifurcation in the ontogram). (C) If T. kansasensis and T. nepaeolicus are the same taxon but neither is necessarily all adults nor all juveniles, and sexual dimorphism is absent, the specimens will be interspersed with each other on the ontogram. (D) If T. kansasensis and T. nepaeolicus are the same taxon but neither is necessarily all adults nor all juveniles, and sexual dimorphism is present, the specimens will be interspersed with each other on the ontogram and on both branches after the onset of sexual maturity. (E) The ontogram is linear with specimens of both taxa interspersed with each other, but identical individual variations are unambiguously optimized in several specimens of one taxon and not along the main axis or in specimens of the other taxon; in this case, two groups are recovered and they may represent two taxa or sexual dimorphism. (F) If T. kansasensis and T. nepaeolicus are opposite sexes of the same taxon, the ontogram will bifurcate with specimens of T. kansasensis on one branch, T. nepaeolicus on the other branch, and a mix of specimens near the root. (G) If T. kansasensis and T. nepaeolicus are two different taxa, the ontogram will bifurcate at or near the root with all the T. kansasensis specimens on one branch and all the T. nepaeolicus specimens on the other; this could also represent sexual dimorphism with an oversampling of adults in which specimens of T. kansasensis represent one sex and specimens of T. nepaeolicus represent the other.