Compsognathus longipes
Compsognathus longipes ("with graceful jaw and long feet") is the only known species of the extinct genus Compsognathus from a compsognathid theropod dinosaur, which lived at the end of the Jurassic period, approximately 150 million years ago, in the Tithonian, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany in the 1850s and the second in France almost a century later. Many popular submissions describe Compsognathus as a rooster-sized dinosaur, due to the smallness of the German specimen, which is now reinterpreted as a juvenile form of the same species as the French specimen, a larger adult. size. Compsognathus is one of the few dinosaurs for which the diet is known with certainty: the remains of small agile lizards are preserved in the bellies of both specimens. Tooth fossils discovered in Portugal can be assigned to the genus.
Although not recognized as such at the time of its discovery, Compsognathus is the first known dinosaur with a fairly complete skeleton. Today, Compsognathus longipes is the only recognized species, although the largest specimen discovered in France in the 1970s was thought to represent a separate new species, C. corallestris. Until the 1990s, Compsognathus was the smallest known dinosaur and the closest known relative of the primitive bird Archaeopteryx.
Description
For decades, Compsognathus was famous for being the smallest known dinosaur; collected specimens are about a meter in length. However, later discovered dinosaurs, such as Caenagnathasia, Microraptor, and Parvicursor, were even smaller. Compsognathus is estimated to have weighed about 3 kilograms.
Compsognathus was a small, bipedal animal with long hind legs and an elongated tail, which it used for balance during locomotion. The front limbs were smaller than the hind limbs and were provided with claws equipped with three strong clawed fingers adapted for catching prey. Its delicate skull was narrow and long, with a pointed snout. The skull had 5 pairs of fenestrae, cranial openings, the longest being the eye sockets, where the eyes are found in the living animal. The eyes were large in proportion to the rest of the skull.
The lower jaw was thin and lacked mandibular fenestrae, pits in the lower jaw commonly seen in archosaurs. The teeth were small but sharp, compatible with their diet of small vertebrates and possibly other small animals, such as insects. Its teeth seen from the front, those of the premaxilla, were not serrated, unlike those that were further back in the jaw. Scientists have used these dental features to identify Compsognathus and its closest relatives. Reisdorf and Wuttke in 2012 described the taphonomic phenomena of the German specimen of Compsognathus .
The Compsognathus specimen discovered in Germany in the 19th century had only two digits in each forelimb, leading scientists to conclude that this was the case in the creature in life. However, a fossil discovered later in France revealed that the hand had three digits, similar to other members of the other genera. compsognathids. Fossilization of the German Compsognathus simply had not fully preserved the specimen's hands. Bidar surmised that the French specimen had webbed hands, which would look like flippers in life. In the 1975 book 'The Evolution and Ecology of Dinosaurs', L. B. Halstead describes the animal as an amphibian dinosaur. capable of feeding on aquatic prey and swimming out of reach of large predators. Ostrom discredited this hypothesis by conclusively demonstrating that the French specimen was nearly identical to the German specimen in all respects except size. Peyer confirmed these conclusions.
Integument
Evidence from related species suggests that the body may have been covered with feather-like structures. Some relatives of Compsognathus, such as Sinosauropteryx and Sinocalliopteryx, have been preserved with the remains of simple feathers covering the body, prompting some scientists to suggest that Compsognathus could have been feathered in a similar way. Consequently, many depictions of Compsognathus show it covered with downy protofeathers. However, no feathers or feather-like sheaths have been preserved with the fossils of Compsognathus, unlike Archaeopteryx, which are found in the same sediments. Karin Peyer, in 2006, reported preserved skin impressions on the tail side starting at the thirteenth tail vertebra. The impressions showed small bumpy tubercles, similar to the scales found on the tail and hind legs of Juravenator. Additional scales had been reported by von Huene in 1901, on the abdominal region of Compsognathus German, but Ostrom later refuted this interpretation. In 2012 they were by Achim Reisdorf seen as adipocere plaques, cadaver 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, although there are some indications 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.
Discovery and research
Two nearly complete skeletons are known of Compsognathus, one in Germany that is 85 cm long, and another in France that is 155 cm long. For almost a century, Compsognathus was the only well-known small theropod. This led to comparisons with Archaeopteryx and suggestions of a relationship to birds. Even Compsognathus and Archaeopteryx piqued Huxley's interest in the origin of birds. The two animals share many similarities in shape, size, and proportions; in fact, a featherless fossil of Archaeopteryx was for many years misidentified as Compsognathus. Many other dinosaurs, including Deinonychus, Oviraptor and Segnosaurus, are now known to be close relatives of birds.
Discovery
Physician and fossil collector Joseph Oberndorfer discovered the German specimen, BSP AS I 563, in the lithographic Solnhofen limestone deposits in the Riedenburg-Kelheim region of Bavaria during the 1850s. Limestone from the Solnhofen area has also produced well-preserved fossils such as Archaeopteryx, with feather impressions, and some pterosaurs with markings from their wing membranes dating to the early Tithonian epoch. Johann A. Wagner described the specimen briefly in 1859 and in more detail in 1861, when he used and coined the term Compsognathus longipes. The generic name comes from the Greek kompsos/κομψος, "elegant", "refined" or "delicate" and gnathos/γναθος; "jaw", the name of the species comes from Latin and means "long-legged". In early 1868, Thomas Huxley hypothesized that the specimen was closely related to dinosaurs, and in 1896, Othniel Marsh recognized the fossil as a true member of the group. John Ostrom redescribed the species thoroughly in 1978, making the dinosaur one of the best-known small theropods to date. The German specimen is on display at the Bayerische Staatsammlung für Paläontologie und historische Geologie (Bavarian State Institute for Paleontology and Historical Geology), in Munich, Germany.
The largest French specimen, MNHN CNJ 79, was discovered in 1972 in the lithographic Portland de Canjuers limestone near Nice in southeastern France. It also dates from the beginning of the Tithonian. Although Bidar originally described the specimen as a separate species named Compsognathus corallestris, Ostrom, Michard, and others have renamed it another specimen of Compsognathus longipes. Quimby identified the specimen as smaller German as a juvenile of the same species. studied there completely.
The collector Heinrich Fischer had originally labeled a partial foot, also from Solnhofen, as belonging to a Compsognathus. Although this identification was rejected by Wilhelm Barnim Dames in 1884, Friedrich von Huene nevertheless provisionally referred the specimen to Compsognathus in 1925. However, Ostrom's 1978 study has disproved this. Jens Zinke in 1998 assigned to the genus forty-nine teeth from the Guimarota Formation of the Kimmeridgian of Portugal. These are not identical to those of C. longipes, serrated on the leading edge, but due to general similarities in shape they were referred to Compsognathus sp..
In 1997, Virginia Morell changed the name of a related Chinese form, Sinosauropteryx prima, to Compsognathus prima, although this has not found general acceptance.
Classification
Compsognathus gives its name to the family Compsognathidae, a group of mostly small dinosaurs from the late Jurassic and early Cretaceous of China, Europe, and South America. For many years this was the only known member; however, in recent decades, paleontologists have discovered several related genera. The clade includes Aristosuchus, Huaxiagnathus, Mirischia, Sinocalliopteryx, Sinosauropteryx, and perhaps Juravenator and Scipionyx. Initially, Mononykus was proposed as a member of this family, but was eventually rejected by Chen and co-authors in a 1998 article; they considered the similarities between Mononykus and compsognathids as an example of convergent evolution. The position of Compsognathus and its relatives within the coelurosaur group is uncertain. Some authors, such as theropod expert Thomas Holtz Jr. and co-authors Ralph Molnar and Phil Currie on the 2004 text The Dinosauria, argue that the family is the most ancient among coelurosaurs, while others authors defend that it is part of Maniraptora.
Paleobiology
In a 2001 study by Bruce Rothschild and colleagues, nine foot bones referred to Compsognathus were examined for signs of stress fracture, but found none.
"Hands"
The Compsognathus specimen discovered in Germany in the 19th century shows only two fingers on each forelimb, leading scientists to conclude that this was its anatomy in life. However, a fossil discovered later in France revealed that the hands had three fingers, similar to other compsognathids. The fossilization of the German specimen simply did not preserve the fingers of the French specimen. Bidar surmised that the French specimen had webbed toes, which would have been seen as flippers in life. In the 1975 book The Evolution and Ecology of Dinosaurs, L. B. Halstead depicted the animal as a dinosaur-amphibian capable of feeding on aquatic prey and swimming out of reach of large predators. Ostrom ridiculed this hypothesis by showing that the French specimen was almost identical to the German specimen in all respects except size. Peyer confirmed these conclusions.
Food
The remains of a lizard in the thoracic cavity of the German specimen show that this animal fed on small vertebrates. Marsh, who examined the specimen in 1881, believed that this small skeleton within the stomach region of the fossil was an embryo, but in 1903, Franz Nopcsa concluded that it was a lizard. Ostrom identified the remains as coming from a lizard of the genus Bavarisaurus, concluding that it was a fast and agile runner due to its long tail and large proportions. of the members (according to a subsequent study made with biomechanical simulations by Bill Sellers and the paleontologist Philip Manning carried out by computer at the English University of Manchester and published in the bulletin Proceedings of the Royal Society , where They assure that it is the fastest biped so far known, being able to reach a maximum speed close to 64 km/h). This led to the conclusion that its predator, Compsognathus, had to have keen vision and the ability to accelerate a hundred meters in just over six seconds to catch up with the lizard. Bavarisaurus it is in one piece, indicating that Compsognathus must have swallowed its prey whole. The gastric contents of the French specimen consist of unidentified lizards or sphenodontids.
Playback
Excavators discovered 10mm-diameter eggs near the fossil remains of the German specimen. In 1901, Friedrich von Huene interpreted these as dermal ossifications. Griffiths redescribed them as immature eggs in 1993. However, later researchers have doubted their assignment to the genus because they were found outside the animal's body cavity. A well-preserved fossil of Sinosauropteryx, a genus related to Compsognathus, shows two oviducts containing two unlaid eggs. These proportionally larger and less numerous eggs of Sinosauropteryx cast further doubt on the original identification of Compsognathus eggs.
Feathers and the Bird Connection
No feather or similar structure has been preserved in fossils of Compsognathus, in contrast to Archaeopteryx, which has been found in the same sediments; thus, many depictions of Compsognathus show it without feathers. Von Huene reported the presence of a fossilized patch of skin on the abdominal region of the German compsognath, but was later refuted by Ostrom. Relatives of Compsognathus, such as Sinosauropteryx and Sinocalliopteryx, have been preserved with remains of single feathers covering the body like fur, indicating that Compsognathus must have possessed similar plumage. In contrast, a patch of skin Fossilized view of the tail and forelimb of another genus of presumed compsognathid, Juravenator, shows only scales, with no indication of feathers in preserved areas. This may mean that the feather cover was not complete in this group of dinosaurs, although a new evaluation by Butler and Upchurch has cast doubt on the assignment of the Juravenator to the same family as the compsognath..
Paleoecology
During the Late Jurassic, Europe was a dry, tropical archipelago at the edge of the Tethys Sea. The fine limestone in which the skeletons of Compsognathus were found, have their origin in calcite from the shells of marine organisms. Both the Solnhofen area and Canjuers, where the Compsognathus were preserved, were located between the beaches and coral reefs of the Jurassic European islands in the Tethys Sea. Some contemporaries of the compsognathus , include the primitive bird Archaeopteryx and the pterosaurs Rhamphorhynchus and Pterodactylus. The same sediments in which the compsognath has been preserved also contain fossils of various marine animals such as fish, crustaceans, echinoderms and mollusks, confirming the coastal habitat of this theropod. No other dinosaur has been found in association with Compsognathus, indicating that this may in fact be the largest terrestrial predator on these islands.
In popular culture
In children's books about dinosaurs, Compsognathus commonly appears. For a long time it was unique as a small dinosaur, with most other small dinosaurs discovered and described a century or so later.
They appear in the film series Jurassic Park, where they are simply referred to as "buddies", and although they are small dinosaurs, they are just as dangerous, attacking in packs. In Michael Crichton's original novel, Compsognathus attack a group of young children at the beginning, and John Hammond's character is mentioned as being killed by these creatures. In the movies, they appear in The Lost World: Jurassic Park attacking a girl at the beginning, then during the expedition on Sorna Island, the hunter Dieter Stark meets these little dinosaurs in the jungle, but unable to escape from a group of them, he is attacked and is torn to pieces by bites. When he dies, the latter screams in Swedish.
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