Figure 2.

Drag coefficients of nine ichthyosaurs and a modern analogue, the bottlenose dolphin. (a,b) CFD-computed total drag coefficients of nine ichthyosaurs and a bottlenose dolphin without (a) and with (b) limbs at Reynolds numbers from 10⁶ to 5 × 10⁷. (c,d) Comparison of the drag coefficients and their mean values (in grey) between taxa, without (c) and with (d) limbs; two-sample t-tests between groups not significant (NS). (e,f) Mean values of the drag coefficient of ichthyosaurs plotted against the mean occurrence age for each taxon, without (e) and with (f) fins; no correlation detected, Kendall's τ = −0.29, p = 0.28, NS (no limbs); Kendall's τ = −0.22, p = 0.39, NS (with limbs). Ichthyosaurs from the ‘basal grade’ are highlighted in yellow, the ‘intermediate grade’ in green and the ‘fish-shaped ichthyosaurs' in blue. The bottlenose dolphin Tursiops is highlighted in red. (g) Two-dimensional plots of flow velocity magnitude (Re = 5 × 10⁶; inlet velocity of 5 m s⁻¹).