Investigations on Cetacea (1972)


Information is communicated on the occurrence of Phoconea spinipinnis off the Uruguayan coast and on the general geographical distribution of this rare species. In contradiction to the observations of ALLEN [1925], the manubrium of our specimen exhibited a 3 mm wide perforation and the 7th cervical vertebra a clearly defined spinous process. The relative skull measurements of adult specimens of Phocoena spinipinnis are compared to those of Ph. dioptrica and Ph. phocoena. The height of the neurocranium varies in the three species, the lowest percentage value being found for spinipinnis and the highest for dioptrica. The three species also differ as regards the length of their upper toothrow (right and left) that is relatively shortest in Ph. spinipinnis and relatively longest in Ph. phocoena. The number of alveoli is also lower in spinipinnis than in phocoena and dioptrica. At the level of the eyes, i.e, across the zygomatic arch, the skull of dioptrica is wider than the skulls of the other two species between which no difference is observed. Ph. spinipinnis has the temporal fossa with the largest area and circumference.