Abstract

(…) The original description of the holotype of P. dioptrica was based on an unique and distinctive color pattern. The dorsal surface and upper lateral surface to just above the’ eye is black, but the dorsal keel of the caudal stock is white (see figure 1). The dorsal surface of the flukes is black and the ventral surface is white with a gray border. The lower lateral surfaces and ventral surface are white. The eyes are surrounded by a wide black eye patch. The pectoral flippers are white and have a clear gray border, and a faint gray “flipper stripe” extends from the angle of the gape to the anterior insertion of the flipper. The general external morphology is as in other species of Phocoena, but dioptrica differs in having pectorals relatively smaller and rounded rather than pointed, and a large triangle shaped dorsal fin in adult males. The skull in general character is like that of P. phocoena, but differs as follows (see figure 2): 1) the dorsal surface of the rostrum is much more flattened, in lateral view the premaxillae are less visible; 2) in lateral view, the dorsal profile of the supraoccipital bone is in line with the dorsal profile of the rostrum instead of tilted at an angle of slightly more than 20 degrees; 3) the condylobasal length of cranium (283 to 315 mm) is greater; 4) the cranium is broader; 5) the rostrum is more acute; and 6) the slope from the vertex of the skull to the nasal orifices is steep, in this resembling Phocoenoides. (…)