Caudipteryx

Cast of a fossil of Caudipteryx zoui in Hong Kong Science Museum.

• China, Liaoning ( Yixian Formation)

• Caudipteryx zoui
• Caudipteryx dongi ( Zhou & Wang, 2000)

Caudipteryx was a feathered theropod dinosaur from the group of Oviraptorosauria from the Lower Cretaceous Liaoning (China). Of this genus two species are known, Caudipteryx zoui and Caudipteryx dongi. It was small, bird -like animals, which had a nearly edentulous beak, secondaries and a short tail that ended in a fan of feathers.

Discoveries and naming

Caudipteryx was founded in 1998 by Ji, Currie, Norell and Ji based on two partial skeletons firstdescribed ( holotype; catalog number NGMC 97-4 A and para-type, catalog number NGMC 97-9 -A). A third Fossil ( catalog number IVPP 1240) was first described in 2000 by Zhou and Wang as Caudipteryx dongi. Caudipteryx zoui means as much as " Zou's tail feather ," said Artepitheth zoui the Chinese vice- Premier Zou Jiahua honors, which supports scientific work in Liaoning. The Artepiteth the second type Caudipteryx dongi honors the Chinese dinosaur experts Dong Zhiming.

The findings come from the Yixian Formation, a company belonging to Jehol Group rock formation, and are dated to the late Barremian to early Aptian.

Features

Like many other Maniraptoren Caudipteryx showed an interesting mix of reptilian and bird-like features. The skull was box-shaped and shorter than the upper thigh bone (femur ), as the Antorbitalregion the skull was shortened (from the eyes ). The elliptical nostrils were bigger than the Antorbitalfenster - a feature of modern birds. The jaws were formed into a beak, the only four teeth on each premaxillary bone ( premaxilla ) showed at the front end of the upper jaw. The crowns were needle-like, the tooth roots were five times wider than the visible part of the teeth.

Caudipteryx had 12 cervical vertebrae, the dorsal vertebrae 9 and 22 caudal vertebrae. The ribs have hook extensions, another characteristic feature for birds. The tail was short and made ​​only a quarter of the body length from. The arms were lean and the hand was 3 metacarpal, said first metacarpal bone was only 40% as long as the second. The third finger was reduced and displayed, only two phalanges, the claw ( ungual ) was missing. The acetabular cup ( acetabulum ) was large and made almost a quarter of the length of the ilium ( ilium ) from - in birds the acetabulum takes only 11 % of the length of the ilium one. The hind legs were thin and more than twice as long as the arms, the metatarsals were extended.

The tail and wing feathers are preserved as a fossil imprints. The wing feathers were 15-20 inches long and formed along the second finger a wing-like compartments. The holotype specimen shows eleven long tail feathers on the left side of the tail, which were probably paired with eleven other springs on the other side of the tail. The springs were just like the contour and flight feathers of modern birds from a spindle, a spring shaft and a spring flag from interlocked beams and hooks. In contrast to the secondaries of Archaeopteryx and modern flying birds the wing feathers of Caudipteryx show no asymmetry.

Paleobiology

Due to the largely toothless beak is suspected of Caudipteryx and other Oviraptorosauriern that it was omnivorous. In two instances ( NGMC 97 4 A and NGMC 97 9 A) gastroliths were found - stones, which swallowed the animals to crush the food in the gizzard. It is rounded, polished pebbles in the stomach region of the specimens, which have a diameter of up to 4.5 mm.

System

Since the initial description by Ji et al. in 1998 the systematic affiliation of Caudipteryx is controversial. Since the fossils unique imprints of feathers show and several cladistic analyzes came to the conclusion that it was a non- avian theropod from the group of Oviraptorosauria, he was at least at the time of description as the clearest indication of a lineage of birds of the dinosaurs. Thus, the paleontologist Lawrence Witmer says: "The presence of unambiguous feathers in to unambiguously nonavian theropod Has the rhetorical impact of an atomic bomb, rendering any doubt about the theropod relationships of birds ludicrous " ( in German as: " The presence of unambiguous feathers in an unequivocal non-avian theropod has the rhetorical impact - a nuclear bomb that can appear any doubt about the relationship of the theropod ridiculous with birds ").

Other paleontologists disagree with that consensus. As suspect Jones et al. (2000) based on mathematical comparison of the body proportions of flightless birds and theropods that Caudipteryx was a flightless bird and a descendant airworthy ancestors. Dyke and Norell (2005 ) found this result, however, in question and pointed to errors in the mathematical methods, and came with their own analysis to the conclusion that Caudipteryx was actually a non-avian theropod -. The view that not only Caudipteryx was a dinosaur -like flightless bird, but even the whole group of Oviraptorosaurier and Deinonychosaurier the offspring earlier ( already airworthy ) were ancient birds and thus belonged even to the group of birds will, among other things, Feduccia et al. (2005) represented. These researchers are of the opinion that the birds are not descended from theropods, but from earlier archosaurs. Osmólska et al. (2004) also came to the conclusion that the Oviraptorosauria including Caudipteryx must be filed within the birds. Unlike them, however, Feduccia, believe that birds and thus the Oviraptorosauria descendants were more primitive theropods.

Caudipteryx is considered a basal ( primitive ) Representatives of Oviraptorosauria. The first description of the species Caudipteryx dongi in 2000, Zhou and Wang presented a new family, the Caudipteridae, which should contain only the genus Caudipteryx with the two species. A definition of this new taxon remained, and then the family contains only one species, that is mono typically, it is considered by many researchers to be redundant and not be accepted. In 2008, He et al described. However, the new genus Similicaudipteryx and they arranged a within the Caudipteridae.