The Malmooth were beings with blue-green, chitinous skin and long heads. They had pairs of mandibles at the side of their human-like mouths, which twitched as they talked. They also had internal milk on which they could feed. Malmooth had what appeared to be an extra pair of nostrils below the first. (TV: Utopia)
The Malmooth social convention required its speakers to divide their name into two syllables and speak them at the beginning and the end of each sentence, for example "Hello" would become "Chan-Hello-tho" in the case of a Malmooth known as "Chantho". To not do this would be akin to swearing in other languages. (TV: Utopia)
With the dying of the universe, the Conglomeration decayed and nearly all of the Malmooth became extinct, save for a young female called Chantho, who worked with Professor Yana at Silo 16 on Malcassairo.
Chantho was later killed when Yana returned to his old self — the Master — in the year 100,000,000,000,000, but not before she shot the Time Lord, triggering his regeneration. With her death the Malmooth became extinct. (TV: Utopia)