WordNet records no synonym and no antonym for mononychus olecranus. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a turkey-sized long-legged fossil 75 million years old found in the Gobi Desert having bird-like fused wrist bones and keeled breastbone and a long tail resembling a dinosaur's; short forelimbs end in a single claw instead of wings; classification as bird or dinosaur is in dispute
Synonyms, antonyms and the broader and narrower relations for mononychus olecranus come from Princeton University’s WordNet. Full sources and licences.