Limusaurus.
Limusaurus is a genus of theropod dinosaur that lived in what is now China during the Late Jurassic, around 161 to 157 million years ago. The only species, Limusaurus inextricabilis, was described in 2009 from specimens (pictured) found in the Upper Shishugou Formation in the Junggar Basin. Limusaurus was a small, slender animal, about 1.7 m (5 ft 7 in) in length and 15 kg (33 lb) in weight, with a long neck and legs but small forelimbs. It underwent a drastic morphological transformation as it aged: while juveniles were toothed, the teeth were completely lost and replaced by a beak. This probably corresponded to a dietary shift from omnivory to herbivory. Since many specimens were found together, it is possible Limusaurus lived in groups. As referenced in its genus name, which means "mud lizard", specimens of Limusaurus appear to have been mired in mud pits created by the footprints of giant sauropod dinosaurs.
