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Mononykus was a theropod dinosaur from late Cretaceous Mongolia (Nemegt Formation, about 70 million years ago) with long, skinny legs. It moved about on two legs, was very nimble, and could run at high speeds, something that would have been useful in the open desert plains where it lived. It had a small skull, and its teeth were small and pointed, suggesting that it ate insects and small animals, such as lizards and mammals. Large eyes allowed Mononykus to hunt by night, when it was cooler and there would have been fewer predators about.


Biology[]

Mononykus was a small dinosaur, only 3 feet (1 m) long. Other characteristics include fused wrist bones similar to those of birds, and a keeled breastbone. It differed from close relatives Shuvuuia and Parvicursor in several details of its skeleton, including a pubic bone that is triangular in cross section, and different proportions in the toe bones.

Mononykus is currently represented by a single holotype specimen, this specimen consists of a partial skeleton lacking a tail, and only small fragments of skull bones, including a complete braincase. Several other specimens were later described, including specimens with complete tails (showing that the tail was relatively short) and complete skulls showing a distinct, mostly toothless form. However, these specimens have since been reclassified in the new genus Shuvuuia. Because of this, many reconstructions of Mononykus in art and mounted skeletons in museums are in fact based mainly on Shuvuuia.

While Mononykus was formally described in the 1990s, it was reported that a specimen possibly belonging this genus had already been unearthed by the Andrews expedition decades before. The specimen had been in the American Museum of Natural History collection, labeled simply as "bird-like dinosaur".However, given the re-assignment of the other specimens to related genera, and the difference in age.

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