Classification: 

Historically, the genus Neophocaena contained only one recognised species, the finless porpoise N. phocaenoides.

It has very recently been split into two species: the Indo-Pacific finless porpoise N. phocaenoides and the narrow-ridged finless porpoise N. asiaeorientalis, formerly recognized as the subspecies N. phocaenoides asiaeorientalis.

Two subspecies are retained within N. asiaeorientalis; the Yangtze finless porpoise N. a. asiaeorientalis (the world’s only freshwater porpoise) and the East Asian finless porpoise or sunameri, N. a. sunameri. 

 

Appearance: 

The two species of finless porpoise are the only members of the porpoise family without a dorsal fin and are easily recognisable at sea.

The low profile makes it nearly invisible if the seas are rough.

Both species of finless porpoise have a dorsal ridge along the back that runs from above the flippers to the beginning of the tail stock.

This ridge is covered in circular wart-like tubercles or bumps, and in the narrow-ridged finless porpoise, as the name would suggest, the tubercules cover a narrow area.

Both species are one of the smallest cetaceans and the only member of the porpoise family to have a bulbous melon - there is no prominent beak. The mouth is small and curves slightly upwards and there is a slight depression behind the blowhole.

Both species of finless porpoise have a small, streamlined body which is pale grey-blue in colour with a lighter belly and white chin.

Adults usually grow to between 1.2 and 2metres in length.

 

Behaviour: 

Both species of finless porpoises are active animals, usually swimming in small groups or alone.

They swim just below the surface of the water with sudden, darting movements.

Little disturbance is caused when they break the surface and they tend to roll onto their sides when doing so.

They have been known to spyhop, but are rarely seen breaching.

They are generally shy, apart from some individuals living in the Yangtze River, China, which have become accustomed to heavy boat traffic. Calves have been sighted riding on the mother's back, gripping the dorsal ridge, and coming out of the water when the mother breathes.