Kirin is an auspicious beast in ancient China mythology. It is said that it only appears when the world is peaceful. It is regarded as a symbol of good luck and has been given many roles in myths and fables.
The appearance of Kirin is consistent with your description: four-hoofed dragon tail with one horn, scales and dark green. In addition, Kirin is also described as having auspicious power, which can bring prosperity, peace and wisdom.
So according to the information you provided, Kirin is a mysterious beast, which was widely used in ancient culture and art in China.