Caudipteryx

''Caudipteryx'' (meaning "tail feather") is a genus of small oviraptorosaur dinosaurs that lived in Asia during the Early Cretaceous, around 124.6 million years ago. They were feathered and extremely birdlike in their overall appearance, to the point that some paleontologists suggested it was a bird. Two species have been described: ''C. zoui'' (the type species), in 1998, and ''C. dongi'', in 2000.

It had a stout trunk, long legs and was probably a swift runner. The discovery of ''Caudipteryx'' has led to many intensive studies and debate over the relationship of birds and dinosaurs.

History

In 1997, several well-preserved dinosaur skeletons were recovered from the Jiulongsong Member of the Chaomidianzi Formation (now Jianshangou Bed of the Yixian Formation), at the Sihetun locality of Liaoning province, China. The fossils were later described in 1998 and used as the type specimens for the new dinosaur taxa ''Caudipteryx'' and '' Protarchaeopteryx''. ''Caudipteryx'' was erected with the type species ''C. zoui'' and the holotype is NGMC 97-4-A, a nearly complete individual preserving conspicuous feather impressions and gastroliths. The paratype is NGMC 97-9-A, another relatively complete individual with feather impressions. The generic name, ''Caudipteryx'', means "tail feather", and the specific name, ''zoui'', is in honor of Zou Jiahua for his prominent support to the scientific community as the vice premier of China.

Around the summer of 1988, a partially complete skeleton of ''Caudipteryx'' lacking the skull was found in sediments of the "Layer 6" of the Yixian Formation, at the Zhangjiagou locality, which is set apart from Sihetun. This specimen, IVPP V 12344, was in 2000 described and designed as the holotype for new species ''Caudipteryx dongi'', and in a similar fashion to previous specimens of the genus, it preserves exquisite traces of feather integument. The specific name ''dongi'' honors Zhiming Dong, a Chinese paleontologist.

Additional specimens

During 2000, Zhong-He Zhou and colleagues described two additional specimens of ''Caudipteryx'', BPM 0001 and IVPP V 12430, referred to ''C. zoui'' and ''C.'' sp. respectively. Both individuals preserve nearly complete skulls and have feather impressions. Further analyses to IVPP V 12430 have revealed the preservation of propatagium on its left arm.

In 2021 Xiaoting Zheng and team described STM4-3 representing an articulated individual lacking the skull and tail tip, including abundant integument, gastroliths, but also a cartilage fragment that was reported to preserve chondrocytes. The specimen was collected from outcrops of the Yixian Formation at Dapingfang Town near Chaoyang city, west Liaoning.

Description

Size

''Caudipteryx'' was a small theropod, measuring long and weighing about based on femur length. Like many other maniraptorans, has a mix of reptile- and bird-like anatomical features.Witmer, L.M. (2005). “The Debate on Avian Ancestry; Phylogeny, Function and Fossils”, ''Mesozoic Birds: Above the Heads of Dinosaurs'' : 3–30.

Skull

It had a short, boxy skull with a beak-like snout that retained only a few tapered teeth in the front of the upper jaw.

Postcranial skeleton

Its short tail was stiffened toward the tip, with few vertebrae, like in birds and other oviraptorosaurs. It has a primitive pelvis and shoulder, and primitive skull details in the quadratojugal, squamosal, quadrate, jugal, and mandibular fenestra (in the cheek, jaw, and jaw joint). It has a hand skeleton with a reduced third finger, like that of early birds and the oviraptorid '' Heyuannia''.Osmolska, H., Currie, P.J., and Barsbold, R. (2004). "Oviraptorosauria." In Weishampel, Dodson, Osmolska (eds.) ''The Dinosauria'', second edition. University of California Press, 2004.

''Caudipteryx'' had uncinate processes on the ribs, birdlike teeth, a first toe which may or may not be partially reversed and overall body proportions that are comparable to those of modern flightless birds.PDF
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Feathers

The hands of ''Caudipteryx'' supported symmetrical, pennaceous feathers that had vanes and barbs, measuring between long. The primary feathers were arranged in a wing-like fan along the second finger, just like primary feathers of birds and other maniraptorans. An additional fan of feathers existed on its tail. The body of ''C. zoui'' was covered in black feathers, with a visible banding pattern preserved on tail feathers.

A study on the number of flight feathers has concluded that ''Caudipteryx'' was secondarily flightless.

Classification

The consensus view, based on several cladistic analyses, is that ''Caudipteryx'' is a basal (primitive) member of the Oviraptorosauria, and the oviraptorosaurians are non-avian theropod dinosaurs. '' Incisivosaurus'' is the only oviraptorosaur that is more primitive.

Halszka Osmólska ''et al.'' (2004) ran a cladistic analysis that came to a different conclusion. They found that the most birdlike features of oviraptorids actually place the whole clade within Aves itself, meaning that ''Caudipteryx'' is both an oviraptorid and a bird. In their analysis, birds evolved from more primitive theropods, and one lineage of birds became flightless, re-evolved some primitive features, and gave rise to the oviraptorids. This analysis was persuasive enough to be included in paleontological textbooks like Benton's ''Vertebrate Paleontology'' (2005).Osmólska, Halszka, Currie, Philip J., Barsbold, Rinchen (2004) ''The Dinosauria'' Weishampel, Dodson, Osmolska. "Chapter 8 Oviraptorosauria" University of California Press.
The view that ''Caudipteryx'' was secondarily flightless is also preferred by Gregory S. Paul,Paul, G.S. (2002). ''Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds.'' Johns Hopkins University Press, Baltimore. Lü ''et al.'',Lü, J., Dong, Z., Azuma, Y., Barsbold, R., and Tomida, Y. (2002). "Oviraptorosaurs compared to birds." In Zhou, Z., and Zhang, F. (eds.), ''Proceedings of the 5th Symposium of the Society of Avian Paleontology and Evolution'', 175–189. Beijing Science Press. and Maryańska ''et al.''

Others, such as Stephen Czerkas and Larry Martin have concluded that ''Caudipteryx'' is not a theropod dinosaur at all. They believe that ''Caudipteryx'', like all maniraptorans, is a flightless bird, and that birds evolved from non-dinosaurian archosaurs.

A weighted cladogram from 2014, using TNT, is shown below.

Relationship with birds

Because ''Caudipteryx'' has clear and unambiguously pennaceous feathers, like modern birds, and because several cladistic analyses have consistently recovered it as a non-avian oviraptorid dinosaur, it provided, at the time of its description, the clearest and most succinct evidence that birds evolved from dinosaurs. Lawrence Witmer stated:
“The presence of unambiguous feathers in an unambiguously non-avian theropod has the rhetorical impact of an atomic bomb, rendering any doubt about the theropod relationships of birds ludicrous.”

However, not all scientists agreed that ''Caudipteryx'' was unambiguously non-avian, and some of them continued to doubt that general consensus. Paleornithologist Alan Feduccia sees ''Caudipteryx'' as a flightless bird evolving from earlier archosaurian dinosaurs rather than from late theropods.Feduccia, A. (1999). ''The Origin and Evolution of Birds''. 420 pp. Yale University Press, New Haven. . Jones ''et al.'' (2000) found that ''Caudipteryx'' was a bird based on a mathematical comparison of the body proportions of flightless birds and non-avian theropods. Dyke and Norell (2005) criticized this result for flaws in their mathematical methods, and produced results of their own which supported the opposite conclusion. Other researchers not normally involved in the debate over bird origins, such as Zhou, acknowledged that the true affinities of ''Caudipteryx'' were debatable.

Paleobiology

Diet

''Caudipteryx'' is thought to have been an omnivore. In at least two specimens of ''Caudipteryx'' (NGMC 97 4 A and NGMC 97 9 A), gastroliths are preserved. As in some herbivorous dinosaurs, the avialan '' Sapeornis'', and modern birds, these gastroliths remain in the position where the animals' gizzards would have been.

Paleoenvironment

All ''Caudipteryx'' fossils were recovered from the Yixian Formation in Liaoning, China. Specifically, they come from a small area of the Jianshangou bed, near the town of Zhangjiakou. They appear to have been fairly common, though isolated to this small region. The specific region in which ''Caudipteryx'' lived was home to the other feathered dinosaurs '' Dilong'' and ''Sinornithosaurus''.

See also

* Dinosaur coloration
* Timeline of oviraptorosaur research

References

External links

*
*
* Australian Museum
Chinese Dinosaurs: ''Caudipteryx zoui''
Retrieved 2007-FEB-19.
* Natural History Museum of Los Angeles County

Retrieved 2007-FEB-19.
* Research Casting International
Life-size model of ''Caudipteryx zoui''
Retrieved 2007-FEB-19.
* CNN
Scientists: Fossils prove that birds evolved from dinosaurs
Retrieved 2007-AUG-10

{{Taxonbar, from=Q131069

Oviraptorosauria
Dinosaur genera
Barremian dinosaurs
Yixian Formation
Fossil taxa described in 1998
Taxa named by Philip J. Currie
Taxa named by Mark Norell
Dinosaurs of China
Feathered dinosaurs