The anatomy of finless porpoises has been relatively well studied, compared with that of some other cetacean species.
For example, the tubercles along the dorsal ridge are known to contain numerous nerve endings that may possess a sensory function.
The auditory system also appears well-developed, with numerous large nerve fibres specialised for rapid communication between the ears and the brain.
On the other hand, sight is relatively poor, with a reduced lens and a limited number of fibres in the optic nerve and to the muscles moving the eyes.

The skeleton is unusually light, accounting for only 5% of the total weight of the animal.
There are between 58 and 65 vertebrae, about half of them in the tail, and with the first three cervical vertebrae fused into a single structure.
There are ten to fourteen pairs of ribs in the chest, and an additional set of vestigial ribs has sometimes been reported in the neck, in association with the seventh cervical vertebra.
There are 44 sets of spinal nerves.

The nasal passage contains nine or ten air sacs, which have a complicated structure, and are capable of sealing off all air within the passage.
Behind these are an additional set of vomeronasal sacs.
The trachea, however, is short, with only four cartilaginous rings.
The stomach has three chambers, there is no caecum, and no distinct difference between the small and large intestines.
The anatomy of finless porpoises has been relatively well studied, compared with that of some other cetacean species. For example, the tubercles along the dorsal ridge are known to contain numerous nerve endings that may possess a sensory function. The auditory system also appears well-developed, with numerous large nerve fibres specialised for rapid communication between the ears and the brain. On the other hand, sight is relatively poor, with a reduced lens and a limited number of fibres in the optic nerve and to the muscles moving the eyes.
The skeleton is unusually light, accounting for only 5% of the total weight of the animal. There are between 58 and 65 vertebrae, about half of them in the tail, and with the first three cervical vertebrae fused into a single structure. There are ten to fourteen pairs of ribs in the chest, and an additional set of vestigial ribs has sometimes been reported in the neck, in association with the seventh cervical vertebra. There are 44 sets of spinal nerves.
The nasal passage contains nine or ten air sacs, which have a complicated structure, and are capable of sealing off all air within the passage. Behind these are an additional set of vomeronasal sacs. The trachea, however, is short, with only four cartilaginous rings. The stomach has three chambers, there is no caecum, and no distinct difference between the small and large intestines.
Finless porpoise