Metraxis

The Metraxis are a sapient mammalian species originally native to the aquatic planet Kinneret. Their traditional form of greeting is the phrase "I acknowledge you".

Biology
The Metraxis are a humanoid species with faces similar to a sea lion's. They are a dioecious race, and females are known to produce milk. Their skin is black and smooth, as if covered in oil, and they storage fat in the abdomen, resulting in a visible "pot belly". They have silvery whiskers on their faces, but no hair whatsoever. They also have large dark eyes which are capable of blinking, just like human eyes. They have several pairs of nostrils.

History
At some point in their history, the Metraxis started suffering from a genetic condition that resulted in sterility, and were forced to reproduce by cloning. However, their cloning techniques were imperfect, and the process resulted in the loss of some genetic information, causing the lifespan of each new generation to become shorter. Believing that something in their homeworld was causing this, a group of Metraxis decided to leave Kinneret behind and built an ark-like spaceship to travel the galaxy, eventually finding a new home that was adequate for them. At this point, seven generations had passed in the ark. Fortunately, radiation leaking from the ship's fission reactor accidentally resulted in a reverse mutation that caused at least some of them to become fertile again, and they successfully settled on their new planet.

Appearances

 * Doctor Who audio - Short Trips, Volume 4 - "A Star is Born", by Richard Dinnick (2011)