The morphology of the Perrin's beaked whale "Mesoplodon perrini" resembles the Hector's beaked whale "M. hectori". Morphological characteristics that set these two species apart include minor differences in the cranium, teeth, and mandible. External appearances of Perrin's beaked whales are typical of "Mesoplodon" beaked whales, with a relatively small head, long thorax and abdomen, deep peduncle, and short tail. Only the original five beached specimens have been accurately measured. From nose to tail, the adult female was approximately 4.4 meters (~14.5 feet), while the adult male was 3.9 meters (~13 feet). The other three specimens were juvenile males, which measured between 2.1-2.4 meters (~7-7.5 ft).