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 Marvin by eating his scorpian- 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 region Nigel was traversing through. A few more are seen on the scrublands, were a terrifying Tarbosaurus, scares off a couple of Mononykus that Nigel had been watching, of course forcing him also to hide.