Temporal range: Late Jurassic
|A restoration of Compsognathus longipes|
| Compsognathus longipes|
Although not recognized as such at the time of its discovery, Compsognathus is the first dinosaur known from a reasonably complete skeleton. Until the 1980s and 1990s, Compsognathus was the smallest known dinosaur and the closest supposed relative of the early bird Archaeopteryx. For nearly a century, Compsognathus was the only well-known small theropod. This led to comparisons with Archaeopteryx and to suggestions of a relationship with birds. The two theropods share many similarities in shape, size and proportions, so many in fact that a featherless skeleton of an Archaeopteryx was for many years misidentified as a Compsognathus. Many other dinosaurs, such as dromeosaurids are known to be related to birds.
Some relatives of Compsognathus have been preserved with the remains of simple feathers covering the body like fur, promoting some scientists to suggest that Compsognathus might have been feathered in a similar way. Consequently, many depictions of Compsognathus show it with a covering of downy proto-feathers. However, no feathers or feather-like covering have been preserved with Compsognathus fossils, in contrast to Archaeopteryx, which was found in the same sediments. In 2006, reported skin impressions preserved on the side of the tail starting at the 13th tail vertebra were found. The impressions showed small bumpy tubercles. Additional scales had earlier been reported in the abdominal region of the German Compsognathus, but this interpretation was later disproved.