Figure 10

Homology of the sea urchin gastric caecum based on its location as a primary criterion. (A-C) Interactive 3D PDF models of the digestive tract of two "regular" [Eucidaris metularia (A), Diadema savignyi (B)] and one irregular [Echinoneus cyclostomus (C)] sea urchin species. Left-click onto each of the three images in order to activate the embedded 3D models. Labeling designates the structures we consider homologous. Note that the 3D model of Diadema savignyi (B) depicts a modelling artefact due to the close proximity of esophagus and rectum: both structures seem to be fused, although they are clearly not in reality. Please refer to [88–90] for an in-depth explanation of how to manipulate and generate publication-embedded 3D PDF models. This interactive 3D figure requires Adobe Reader 8.0 or higher to operate. Not to scale.