These two patches are connected by a thin white strip, creating, loosely speaking, an hourglass shape; hence the common name of the dolphin.

The dorsal fin in hourglass dolphins is variable and the curvature may be particularly pronounced in older animals.

The hourglass dolphin has disk-shaped vertebrae and other inclined processes which gives them higher stability.

Males are thought to be slightly smaller and lighter than females, although the small number of specimens does not permit a firm conclusion.

Female gestation periods are estimated to be 12.9 months and they tend to give birth between mid to late July through October.

[3] The northernmost confirmed sightings are 36°S in the South Atlantic Ocean and 33°S near Valparaíso, Chile, in the Pacific.

This species prefers colder water so they spend most time closer to the surface where the temperature is around -0.3°C to 7°C.

Examinations of the stomach contents of the few specimens indicate they eat mantis shrimp, polychaete worms, and various (unrecorded) species of squid and small fish.

[4] Lesson and Garnot (1827) named another dolphin with two white patches on the sides Delphinus bivittatus.

[18] They are also listed in Appendix II of the Convention on International Trade in Endangered Species (CITES).