Mononykus did not appear in the main series.
SpecialsEditMononykus appeared in 'The Giant Claw', the second episode of Chased By Dinosaurs.
It was shown to be a nocturnal omnivore, pestering Nigel Marven by eating his pet scorpion- though he pestered them back by running after one and catching it. They were shown to be feathered Dinosaurs very closely related to modern birds. A flock of Mononykus inhabit the jungle-like region Nigel was traversing through. A few more are seen on the scrub-lands, were a terrifying Tarbosaurus, scares off a couple of Mononykus that Nigel had been watching, of course forcing him to hide too.