Posterior and lateral semicircular canal size with respect to skull length.

<p>(A) Posterior semicircular canal (PSC) area enclosed versus skull length, and (B) Lateral semicircular canal (LSC) area enclose versus skull length. Skull length significantly correlates with both PSC and LSC area enclosed in both bipedal and quadrupedal dinosaurs. The PSC regressions of the two groups are similar in slope and regression intercept, indicating that skull length cannot be used with PSC size to distinguish bipeds from quadrupeds. The LSC regressions of the two groups also share a common slope, but are significantly separated by regression intercept with the bipeds elevated above the quadrupeds. This separation is similar to the anterior semicircular canal (ASC) size comparison with skull length and much less robust than the ASC size comparison with estimated head mass (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0058517#pone-0058517-g003" target="_blank">Figure 3</a>). Solid lines: standardized major axis regressions for significant correlations, dashed lines: phylogenetically correct ordinary least square regression (PCOLS), and dotted lines: 95% confidence interval for each group around the PCOLS. •: bipeds, ▴: quadrupeds, and ▪: taxa with ambiguous posture.