Ontogenetic transformation series for Chasmosaurus specimens.

Strict consensus of 24 most parsimonious trees (TL = 40 steps, CI = 0.65, RI = 0.81) using 18 cranial characters. Bootstrap replicate frequency is shown above each node (only Bootstrap values of 50% or higher are given); Bremer values are shown above each node, in italics. Characters and associated states (shown in brackets) are shown on left and are mapped at their earliest occurence on the tree. These character state changes represent an inferred sequence of development; however, due to variable timing of character changes amongst specimens, this sequence is an approximation. Below each specimen is the previous taxonomic designation; state reversals are listed below. In box to the right of each specimen, rostral-to-epijugal length (top, bold, in mm; parameter 16, Fig 2) and squamosal length (bottom, in mm; parameter 19, Fig 2) are given for skull size reference, where preserved. Although TMP 1998.128.0001 was not included in the analysis, its basal position on the tree is indicated by a dashed line, inferred based on its small size and possession of immature character states (12(0), 13(0), and 14(0)). Boxes at bottom delimit age classes (see text for definitions); numbers below each box represent rostral-to-epijugal lengths (in mm) for each age class (est. = estimated). [planned for page width].