(…) Watkins et al. (1977) and Dudok van Heel (1981) point to similarity in sound output in Cephalorhynchus and Phocoena, and suggest that it may be the result of convergent evolution, due to a similar ecological conditions, i.e. life in a coastal or estuarial, shallow water habitat. This suggestion, together with evidence that sounds are generated with forehead, soft-tissue structures (possibly involving the fatty bursa), are compelling reasons to undertake a detailed comparative study of their forehead anatomy.
In this presentation, we approach the problem of describing complex 3-D anatomy by using high resolution, computer generated stereograms based on serial, 2-D sections which depict structures that we believe are important to sonar signal generation in Phocoena phocoena and Cephalorhynchus commersonii. Stereograms allow the viewer’s brain to reconstruct the morphology in three dimensions. (…)