Psittacosaurus sinensis

Psittacosaurus was an early ceratopsian from the Early Cretaceous of China, roughly 125–110 million years ago. About a meter long, Psittacosaurus was a small bipedal plant-eater named for its deep, parrot-like beak. It is known from several species (with some debate over which ones are valid) that extend over ~15 million years - a long time for a dinosaur genus. Psittacosaurs are basal enough to predate the large frills and horns of later ceratopsians.

Specimen IVPP 12-0888-2 was originally described in 1996 as the type specimen of a new species of Psittacosaurus, P. neimongoliensis. In 2010 it was suggested that the 1996 paper failed to distinguish it from P. sinensis, and no one has challenged it in a peer-reviewed paper since, so I am following it here. But perhaps someone will take a closer look at IVPP 12-0888-2 in the future?

Meanwhile, with hundreds of specimens and still over half a dozen species, Psittacosaurus is one of of the best documented Mesozoic dinosaurs. One specimen of Psittacosaurus preserves extensive skin impressions, showing it was scaly over most of the body, but had a dense row of quills running down the midline of the front part of the tail. Preserved melanosomes in the scales show that the specimen was countershaded - meaning it was darker colored on top and lighter on the bottom. This is a common type of coloration for animals that have to hide, as the lighter bottom half is naturally shaded from the sun, making them look flatter and blending in better to the surrounding environment.