Figure 3.

Relative drag per unit volume of ichthyosaurs. (a,b) Normalized drag per unit of volume without (a) and with (b) limbs, for nine ichthyosaurs scaled to the same total length and tested at the same speed, relative to the values for a bottlenose dolphin (mean ± s.d.). Two-sample t-test ***p = 0.00044 (no fins), **p = 0.0037 (full body) between the ‘basal grade' and the rest of ichthyosaurs. (c,d) Normalized drag per unit of volume without (c) and with (d) limbs for nine ichthyosaurs scaled to the same volume and tested at the same speed, relative to the values for a bottlenose dolphin (mean ± s.d.). No significant differences detected between ichthyosaur grades.