Chimeron

The Chimeron were a race of Humanoids who were nearly wiped out.

Biology
Chimerons hatched from large grey eggs and started as green, wrinkly infants. Though males kept this appearance throughout their life, the queens of the species had a slightly different development. In order to properly develop, the young queens were given a special substance from birth onwards. In the first few hours, they rapidly grew and became more Human-like, developing hair and other more distinct facial features starting to lose their wrinkles. Chimeron queens also developed a strong singing voice at this age, partly as communication and partly as a powerful means of defence. Once they reached the Singing Time, they perfected their defensive songs and reached closer to adult size. Adult queen Chimerons looked similar to Human females with slightly green skin and grey patches behind the ears for detecting higher frequencies.

History
The Chimerons were nearly wiped out by the Bannermen, but one of the last queens, Delta, was able to escape with an egg. The egg hatched on Earth, and with the assistance of the Doctor, Delta and her daughter were able to escape annihilation by the Bannermen. They eventually left Earth in the company of a young Human named Billy who had fallen in love with Delta and took a serum, actually Chimeron baby food, that began to transform him into a Chimeron. (DW: Delta and the Bannermen)