Fig. 3. Schematic diagrams showing landmarks for measurements of the bowhead mouth's anterior and posterior openings (AO and PO, respectively) used in constructing mathematical and physical models. (A) Transverse section at front of oral cavity shows the relationships of tongue, lips and baleen, and the locations of anterior vertical (dorsoventral; AV) and horizontal (frontal plane; AH) dimensions. Specific demarcations of all measures defined in text and in Table 1. (B) Lateral view at rear of mouth, showing locations of posterior vertical and horizontal (PV, PH, respectively) dimensions where filtered water exits this unidirectional flow system; compare to Fig. 1 for a wider view.