At birth, M. peruvianus is between 1.5-1.6 m long, while the adult is between 3.4-3.7 m. This whale is the smallest species of Mesoplodon (World Biodiversity Database, 2001). This species is, on its upper side, uniformly dark gray fading to light gray on the underside (dark gray posterior to the navel). The body is spindle-shaped. The short, dark-tipped beak precedes a narrow head with an indentation at the blowhole. This species has two tiny teeth on its lower jaw. The small, triangular dorsal fin has a wide base and is positioned far behind the center of the animal. The flukes have no notches, and their tips are slightly pointed. (All information from Texas A&M University - Corpus Christi, 2001 unless otherwise noted.)
M. peruvianus exhibits sexual dimorphism. The males of the species are larger than the females (World Biodiversity Database, 2001).
The features that distinguish this Mesoplodon species from others of its genus are most prominent in males (Webb, 1998).
Range length: 3.4 to 3.7 m.
Other Physical Features: endothermic ; bilateral symmetry