Figure 5. Differences of morphological traits between Lutrinae, Pinnipedia, and terrestrial Caniformia are highlighted by side-to-side comparison. A, the ratio of tympanic membrane area to oval window area is drastically altered in aquatic specimens when compared to their terrestrial relatives. The ratio of seals is significantly smaller, but the same effect is visible in oưers albeit to a smaller degree. B, the distance between the tympanic sulcus and the oval window is drastically altered in aquatic species. There is however liưle difference between oưers (Lutrinae) and seals (Pinnipedia). C, comparison of the area size of the opening of the ECF/canaliculus cochleae, normed for body-length of all specimens with sufficient scan resolution (N = 35). Direct comparison shows clear differentiation between pinnipeds and the other groups, displaying an increase in area size of the opening. * = P ≤ 0.05, ** = P ≤ 0.01, ***= P ≤ 0.001, **** = P ≤ 0.0001.