Compsognathus
Compsognathus is a genus of small, bipedal, carnivorous theropod dinosaur. Members of its single species Compsognathus longipes could grow to around the size of a turkey. They lived about 150 million years ago, during the Tithonian age of the late Jurassic period, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany in the 1850s and the second in France more than a century later. Today, C. longipes is the only recognized species, although the larger specimen discovered in France in the 1970s was once thought to belong to a separate species and named C. corallestris.
Many presentations still describe Compsognathus as "chicken-sized" dinosaurs because of the size of the German specimen, which is now believed to be a juvenile. Compsognathus longipes is one of the few dinosaur species whose diet is known with certainty: the remains of small, agile lizards are preserved in the bellies of both specimens. Teeth discovered in Portugal may be further fossil remains of the genus.
Although not recognized as such at the time of its discovery, Compsognathus is the first theropod dinosaur known from a reasonably complete fossil skeleton. Until the 1990s, it was the smallest-known non-avialan dinosaur, with the preceding centuries incorrectly labelling them as the closest relative of Archaeopteryx.
Description
For decades, Compsognathus were famed as the smallest dinosaurs known; the first specimen collected was around in length. However, dinosaurs discovered later, such as Caenagnathasia, Microraptor and Parvicursor, were even smaller. The largest Compsognathus specimen is estimated to have weighed somewhere between.Compsognathus were small, bipedal animals with long hind legs and longer tails, which they used for balance during locomotion. The forelimbs were smaller than the hindlimbs. The hand bore two large, clawed digits and a third, smaller digit that may have been non-functional. Their delicate skulls were narrow and long, with tapered snouts. The skull had five pairs of fenestrae, the largest of which was for the orbit, with the eyes being larger in proportion to the rest of the skull.
The lower jaw was slender and had no mandibular fenestra, a hole in the side of the lower jawbone commonly seen in archosaurs. The teeth were small but sharp, suited for its diet of small vertebrates and possibly other small animals, such as insects. Its frontmost teeth were unserrated, unlike those further back in the jaw which were flattened and more strongly recurved. Scientists have used these dental characteristics to identify Compsognathus and its closest relatives. Reisdorf and Wuttke described the taphonomical phenomena of the German specimen of Compsognathus.
The number of digits on the hand of Compsognathus has been a source of debate. For much of its history, Compsognathus was typically depicted with three digits, as is typical for theropods. However, the type specimen only preserved phalanges from the first two digits, leading to the suggestion that Compsognathus bore only two functional digits, with the third metacarpal being extremely slender and reduced. Study of the French specimen indicated that the third digit bore at least one or two small phalanges. However, there remains no evidence for an unugal phalanx on the third digit, so the digit may have been reduced and non-functional. Bidar supposed that the French specimen had webbed hands, which would look like flippers in life. In the 1975 book The Evolution and Ecology of the Dinosaurs, L. B. Halstead depicts the animal as an amphibious dinosaur capable of feeding on aquatic prey and swimming out of reach of larger predators. Ostrom debunked this hypothesis by showing conclusively that the French specimen was nearly identical to the German specimen in every aspect but its size. Peyer confirmed these conclusions.
Integument
Some relatives of Compsognathus, namely Sinosauropteryx and Sinocalliopteryx, 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 them with coverings of downy proto-feathers. However, no feathers or feather-like covering have been preserved with Compsognathus fossils, in contrast to Archaeopteryx, which are found in the same sediments. Karin Peyer, in 2006, reported skin impressions preserved on the side of the tail starting at the 13th tail vertebra. The impressions showed small bumpy tubercles, similar to the scales found on the tail and hind legs of Juravenator. Additional scales had in 1901 been reported by Von Huene, in the abdominal region of the German Compsognathus, but Ostrom subsequently disproved this interpretation; in 2012 they were by Achim Reisdorf seen as plaques of adipocere, corpse wax.Like Compsognathus, and unlike Sinosauropteryx, a patch of fossilized skin from the tail and hindlimb of the possible relative Juravenator starki shows mainly scales, though there is some indication that simple feathers were also present in the preserved areas. This may mean that a feather covering was not ubiquitous in this group of dinosaurs, or maybe that some species had fewer feathers than others.
Discovery and species
Compsognathus is known from two almost complete skeletons, one from Germany that is long and another from France that is long. The physician and fossil collector Joseph Oberndorfer acquired the German specimen in 1859, discovered about the same year in the lithographic limestone deposits in the Riedenburg-Kelheim region of Bavaria, in the Jurassic part of a lagoonal region known as the Solnhofen archipelago. The limestone of this area has also yielded such well-preserved fossils as Archaeopteryx with feather impressions and some pterosaurs with imprints of their wing membranes. The German Compsognathus fossil itself most likely came from the Painten Formation of the Kapfelberg locality, specifically dated to the uppermost Kimmeridgian stage ; however, alternative possibilities include quarries near Jachenhausen or Goldberg, both from the Tithonian, to which stage Compsognathus has traditionally been dated. Johann A. Wagner discussed the specimen briefly in 1859, when he coined the name Compsognathus longipes, and described it in detail in 1861. In early 1868, Thomas Huxley compared the two species and, following earlier suggestions by Karl Gegenbaur and Edward Drinker Cope, concluded that, apart from its arms and feathers, the Archaeopteryx skeleton was closely similar to Compsognathus, and that the proto-bird was related to the dinosaurs. In 1896, Othniel Marsh recognized the fossil as a true member of the Dinosauria. John Ostrom thoroughly redescribed the species in 1978, making it one of the best-known small theropods at that time. The German specimen is on display at the Bayerische Staatsammlung für Paläontologie und historische Geologie in Munich, Germany, which bought the fossil from Oberndorfer in 1865.The larger French specimen was discovered by quarry owner Louis Ghirardi around 1971 in the Portlandian lithographic limestone of Canjuers near Nice in southeastern France. It dates to the lower Tithonian. Although Alain Bidar originally described the specimen as a separate species called Compsognathus corallestris, Ostrom, Jean-Guy Michard and others have since relabeled it as another example of Compsognathus longipes. Quimby identified the smaller German specimen as a juvenile of the same species. In 1983, the National Museum of Natural History in Paris acquired the French Compsognathus fossil; Michard thoroughly studied it there.
Collector Heinrich Fischer had originally labeled a partial foot, from the Solnhofen area, as belonging to Compsognathus longipes. Though this identification was rejected by Wilhelm Barnim Dames in 1884, Friedrich von Huene nevertheless in 1925 provisionally referred the specimen to Compsognathus. However, Ostrom's study of 1978 has disproven this. Jens Zinke in 1998 assigned forty-nine teeth from the Kimmeridgian Guimarota formation of Portugal to the genus. These were not identical to those of C. longipes, having serrations on the front edge, but were because of general similarities in form referred to a Compsognathus sp.
In 1997 Virginia Morell renamed a related Chinese form, Sinosauropteryx prima, into a Compsognathus prima; this has found no general acceptance.
Classification
The genus Compsognathus gives its name to the family Compsognathidae, a group composed mostly of small dinosaurs from the late Jurassic and early Cretaceous periods of China, Europe and South America. For many years it was the only member known; however, in recent decades paleontologists have discovered several related genera. The clade includes Aristosuchus, Huaxiagnathus, Mirischia, Sinosauropteryx, and perhaps Juravenator and Scipionyx. At one time, Mononykus was proposed as a member of the family, but this was rejected by Chen and coauthors in a 1998 paper; they considered the similarities between Mononykus and the compsognathids to be an example of convergent evolution. The position of Compsognathus and its relatives within the coelurosaur group is uncertain. Some, such as theropod expert Thomas Holtz Jr. and co-authors Ralph Molnar and Phil Currie in the landmark 2004 text Dinosauria, hold the family as the most basal of the coelurosaurs, while others as part of the Maniraptora.For almost a century, Compsognathus longipes was the only well-known small theropod species. This led to comparisons with Archaeopteryx and to suggestions of an especially close relationship with birds. In fact, Compsognathus, rather than Archaeopteryx, piqued Huxley's interest in the origin of birds. The two animals share similarities in shape and proportions, so many in fact that two specimens of Archaeopteryx, the "Eichstätt" and the "Solnhofen", were for a time misidentified as those of Compsognathus. Many other types of theropod dinosaurs, such as maniraptorans, are now known to have been more closely related to birds.
Below is a simplified cladogram placing Compsognathus in Compsognathidae by Senter et al. in 2012.