Compsognathidae is a family of coelurosaurian theropod dinosaurs. Compsognathids were small carnivores, generally conservative in form, hailing from the Jurassic and Cretaceous Periods. The bird-like features of these species, along with other dinosaurs such as Archaeopteryx inspired the idea for the connection between dinosaur reptiles and modern-day avian species.[5] Compsognathid fossils preserve diverse integument — skin impressions are known from four genera commonly placed in the group, Compsognathus, Sinosauropteryx, Sinocalliopteryx, and Juravenator.[6] While the latter three show evidence of a covering of some of the earliest primitive feathers over much of the body, Juravenator and Compsognathus also show evidence of scales on the tail or hind legs. "Ubirajara jubatus", informally described in 2020, had elaborate integumentary structures on its back and shoulders superficially similar to the display feathers of a standardwing bird-of-paradise, and unlike any other non-avian dinosaur currently described.
The first member of the group, Compsognathus, was discovered in 1861, after Johann A. Wagner published his description of the taxon.[7][8][9] The family was created by Edward Drinker Cope in 1875.[10] This classification was accepted by Othniel Charles Marsh in 1882, and added to the Coelurosauria clade by Friedrich von Huene in 1914 after additional fossils had been found.[7] With further discoveries, fossils have been uncovered across three different continents, in Asia,[11][7][8][9][6] Europe,[12] and South America.[8][10] Assignment to Compsognathidae is usually determined through examination of the metacarpal, which is used to separate Compsognathidae from other dinosaurs.[13] However, classification is still complicated due to similarities to the body of several other theropod dinosaurs, as well as the lack of unifying, diagnostic features that are shared by all compsognathids.[10][14] It has been proposed that at least some compsognathids represent juvenile specimens of larger tetanuran theropods, such as carnosaurs.[15]
The first significant fossil specimen of Compsognathidae was found in the Bavaria region of Germany (BSP AS I 563) and given to collector Joseph Oberndorfer in 1859.[16] The finding was initially significant because of the small size of the specimen. In 1861, after an initial period of review, Johann A. Wagner presented his analysis of the specimen to the public and named the fossil Compsognathus longipes ("elegant jaw").[17] In 1868, Thomas Henry Huxley, an early supporter of Charles Darwin and his theory of evolution, used Compsognathus in a comparison to similar feathered dinosaur Archaeopteryx in order to propose the origin of birds. Huxley noticed that these dinosaurs shared a similar layout to birds and proposed an exploration of the similarities. He is credited as being the first person to do so.[18] This initial comparison sparked the interest into the origin of birds and feathers. In 1882, Othniel Charles Marsh named a new family of dinosaurs for this species Compsognathidae and officially recognized the species as part of Dinosauria.[19]
In 1971, a second nearly complete specimen of Composgnathus longipes was found in the area of Canjuers, which is located in the southeast of France near Nice.[7] This specimen was much larger than the original German specimen, but similarities led to experts categorizing the fossil as an adult Compsognathus longipes and leading to the further classification of the German specimen as a juvenile.[20] This specimen also contained a lizard in the digestive region, further solidifying the theory that compsognothids consumed small vertebrate species.