Figure 13. Ontogram of one Tylosaurus sp. specimen, 11 Tylosaurus kansasensis specimens, and seven Tylosaurus nepaeolicus specimens based on a quantitative cladistic analysis.

Specimens identified as T. nepaeolicus are shown in magenta, and specimens identified as T. kansasensis are shown in yellow; the type specimen of each taxon is indicated by an asterisk. The ontogram is a single tree and tree statistics are summarized in the upper left. Character states that define each growth stage are shown along the main branch, and the exemplar specimens are to the left of the main branch; the most mature individuals, identified by the analysis with an artificial adult, are indicated by arrows. The encircled numbers on the nodes are the growth stages, and the numbers to the right of them are the bootstrap and jackknife values, respectively (1000 replicates, < 50% not shown). Unambiguous character reversals are shown in red. “Immature” specimens were recovered in the lower third of the tree, “intermediate” specimens were recovered in the middle third of the tree, and “mature” specimens were recovered in the upper third of the tree. The ontogram does not bifurcate and thus supports synonymy of T. kansasensis with T. nepaeolicus and that T. kansasensis represent juveniles of T. nepaeolicus (Jiménez-Huidobro, Simões & Caldwell, 2016), and does not show evidence for sexual dimorphism. Specimen photographs are not to scale; FHSM VP-14845 is a neonate only referable to Tylosaurus sp.; the photographs of FGM V-43, FHSM VP-2209, AMNH FARB 1565, and FHSM VP-78 have been inverted to face left.