Steggosian

The Steggosians were a race of aliens, described by the Tenth Doctor as "fascist dinosaur people."

Biology
They were approximately six feet wide, with scaly skin, flat heads, big plates running down their backs, and spiky tails. (PROSE: The Eyeless)

History
At some point, the Corsair literally lost his shirt to a Steggosian in a cards game aboard a blimp. (PROSE: The Bloodletters)

Circa the late 1980s, they suffered a terrible plague which had been carried by rats and were wiped out except for a starship crew who had been in deep space at the time. The captain, driven mad, decided to rid the universe of all mammals. After twenty years (during which time the rest of his crew died), he came to Earth, where he planned to release from the recently-rebuilt Big Ben a poison powerful enough to kill everyone in the country. The Doctor arrived to stop him, and during their fight the captain lost his balance and fell to his death, ending the Steggosian race. (PROSE: The Eyeless)