What is the difference between a dolphin and a porpoise?

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1. 1

   Porpoise (Wikipedia)

   WikipediaPublished Oct 15, 2026Checked Oct 17, 2026

   “Porpoises () are small dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and belugas. There are eight extant species of porpoise, all among the smallest of the toothed whales. Porpoises are distinguished from dolphins by their flattened, spade-shaped teeth distinct from the conical teeth of dolphins, and lack of a pronounced beak, although some dolphins (e.g. Hector's dolphin) also lack a pronounced beak. Porpoises, and other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulates. Porpoises range in size from the vaquita, at 1.4 metres (4 feet 7 inches) in length and 54 kilograms (119 pounds) in weight, to the Dall's porpoise, at 2.3 m (7 ft 7 in) and 220 kg (490 lb). Several species exhibit sexual dimorphism in that the females are larger than males. They have streamlined bodies and two limbs that are modified into flippers. Porpoises use echolocation as their primary sensory system. Some species are well adapted for diving to great depths. As all cetaceans, they have a layer of fat, or blubber, under the skin to keep them warm in cold water.”

2. 2

   Harbour porpoise (Wikipedia)

   WikipediaPublished Oct 15, 2026Checked Oct 17, 2026

   “The harbour porpoise (Phocoena phocoena) is one of eight extant species of porpoise. It is one of the smallest species of cetacean. As its name implies, it stays close to coastal areas or river estuaries, and as such, is the most familiar porpoise to whale watchers. This porpoise often ventures up rivers, and has been seen hundreds of kilometres from the sea. The harbour porpoise may be polytypic, with geographically distinct populations representing distinct races: P. p. phocoena in the North Atlantic and West Africa, P. p. relicta in the Black Sea and Sea of Azov, an unnamed population in the northwestern Pacific and P. p. vomerina in the northeastern Pacific.”

3. 3

   A contribution to the anatomy of two rare cetacean species: The hourglass dolphin (Cephalorhynchus cruciger) and the spectacled porpoise (Phocoena dioptrica).

   Anatomical record (Hoboken, N.J. : 2007) (Graïc et al.)Published Oct 22, 2025Checked Oct 17, 2026

   “We present a comprehensive analysis of the gross macroscopical and microscopical morphology of two hourglass dolphins and four spectacled porpoises. Morphometric measurements and skeletal characteristics aligned with the literature, while internal anatomy (organs and systems) was similar to other odontocetes. Precise and consistent lung measurements were challenging; qualitative assessments indicated relatively large lungs with respect to body size. The spectacled porpoise dorsal fin was uniquely large with a well-developed blood supply; this is hypothesized to act as a thermoregulatory window, though it may also play a role in sexual display in the case of males. Overall, this study provides new data on the anatomy of the hourglass dolphin and spectacled porpoise, contributing insights that may influence future research on these rare species. The findings highlight the importance of anatomical studies as a basis for explaining evolutionary relationships within cetaceans and their ecological roles in the Southern Ocean ecosystems.”

4. 4

   Morphological features of the orbicularis oculi muscle and facial nerve in four odontocete families, with comparisons within Cetartiodactyla.

   The Journal of veterinary medical science (Nishimaniwa et al.)Published Nov 5, 2025Checked Oct 17, 2026

   “However, in specimens from Phocoenidae and Delphinidae, the OC featured a muscular area with muscle fibers and an aponeurotic area comprising collagen fibers lacking facial nerve distribution. Our results suggest that this aponeurotic area was acquired in the common ancestor of species within the Delphinoidea superfamily, and that the upper eyelid is less mobile than the lower eyelid. The palpebral branches, which originate from the facial nerve, extend from the lower to the upper palpebral regions in the examined odontocetes, showing a clear difference from the entry course seen at the lateral canthus in artiodactyls. The proximal palpebral branches diverged directly from the facial nerve trunk, forming a characteristic diverging point distal to that of artiodactyls. These branches probably correspond to the auriculopalpebral nerve, which has lost the rostral auricular branch component. The morphological changes in cetacean heads also led to changes in the branching pattern and pathway of the facial nerve.”