Gobipteryx

Gobipteryx
Temporal range: Late Cretaceous, 75Ma
↓
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subclass: †Enantiornithes
Order: †Gobipterygiformes
Family: †Gobipterygidae
Genus: †Gobipteryx
Elżanowski, 1974
Species: † G. minuta
Binomial name
Gobipteryx minuta
Elżanowski, 1974
Synonyms

Gobipteryx (from Gobi [referring to the Gobi Desert where it was first discovered], Greek pteron “wing”) is a genus of prehistoric bird from the Campanian Age of the Late Cretaceous Period.[1] It is not known to have any direct descendants.[1] Like the rest of the enantiornithes clade, Gobipteryx is thought to have gone extinct near the end of the Cretaceous.[2]

Description

Based on a skull length of 45 millimeters, Gobipteryx has been estimated to be approximately the size of a partridge.[3] Its bones are fibrolamellar.[4]

Skull

The skull’s general shape is gradually tapering toward the front.[1] Gobipteryx has a toothless beak[1] formed from the fusion of the premaxillae bones.[5] The skull is characterized as being rhynchokinetic[1] with the pterygoid bones articulating with both the vomers[3][6] and the palatine.[1][3] The nares are tear shaped and the choana is located below them, more rosteral than in most modern birds.[7] The nares are smaller than the antorbital fenestrae, a primitive feature for ornithurae birds.[7] In addition, Gobipteryx's skull has an articulated rostrum.[7] The jaw hinge is associated with the articulation of the quadrate with the pterygoid processes.[1] The articular region of the mandible contains internal and retroarticular processes and has uniform symphysis.[1] This animal has a large, uniform, and sutureless braincase.[1]

Vetebral Column

The vertebral column consists of at least 19 presacral vertebrae, the last 6 of these being dorsals.[8] The neural spines of the twelfth and thirteenth vertebrae form the nuchal blade, which represents the point of greatest elevation in the vertebral column.[8]

Shoulder Girdle

The scapula contains a prominent glenoid labrum and tapers backward, ending as thin rods.[8] The coracoids are slightly concave anteriorly and are separate from the scapulae dorsally. They also stick out from the neck on either side.[8] Gobipteryx's clavicles curve in a way that is consistent with that of other birds.[8]

Limbs

The humerus is posteriorly convex (a normal trait for birds) and the head is comma-shaped.[8] Gobipteryx's ulna is about twice as thick as the radius.[8] Metacarpals II and III have been found in embryonic fossils and are observed to be about equal size and are in close contact with each other.[8]

Paleobiology

Flight

Gobipteryx is believed to have been capable of flight.[4][8] The scapula is long, and therefore, well suited for flight by having more area for muscle attachment.[8] In addition, the forelimb of Gobipteryx is more than twice the length of the thorax, falling within the acceptable range observed in flying birds.[8]

Development

Gobipteryx, along with other enantiornithes, is thought to have superprecocial development, in which it was capable of flying upon hatching.[4][8] Evidence for this comes from the fact that the forelimbs and shoulders of advanced embryos are almost completely ossified.[8] In addition, the growth of G. minuta has been shown to slow down immediately following hatching.[4] This suggests that it was highly mobile in its life, since locomotion has been shown to slow the growth of young birds by focusing energy and resources elsewhere.[4] This onset of flight so early in life is not seen in most modern birds, which begin flying when they have reached or are close to full size.[4]

History

The first specimens were two damaged skulls discovered as part of the 1971 Polish-Mongolian Paleontological Expedition to the Gobi Desert byt Dr. Teresa Maryańska,[1] however, at the time, it was not immediately recognized that both of these skulls belonged to Gobipteryx.[3][6] It was first found in the sandstones of the Lower Nemegt Beds of the Barun Goyot Formation of the Nemegt Basin.[1] The holotype specimen is housed at the Institute of Paleobiology of the Polish Academy of Sciences[8] in Warsaw, Poland and was first described by Dr. Andrzej Elżanowski using a single damaged skull.[1] Initially, Gobipteryx was classified as a member of the clade Palaeognathae on the basis of its jaw and palate.[1] However, in 1981, Dr. Cyril Walker defined the clade enantiornithes[9] and Gobipteryx was reclassified as an enantiornithes bird.

In 1996, Evgeny Kurochkin described a new bird known as Nanantius valifanovi also from the Barun Goyot Formation.[10] However, it was later discovered that N. valifanoi was actually a new misidentified specimen of Gobipteryx minuta.[7] The mistake was, at least in part, due to a misidentification of the maxilla and dentary bones of the skull.[7]

In 1994, an expedition to the Gobi Desert was conducted by the American Museum of Natural History and the Mongolian Academy of Sciences, where a well preserved Gobiptetyx minuta skull was found in the Nemegt Basin.[7] This new specimen provided further evidence for the placement of Gobipteryx into enantiornithes.[7] In addition, it allowed for the reconstruction of the palate, which was poorly understood in Mesozoic birds.[7]

Also during the 1971 Polish-Mongolian Paleontological Expedition to the Gobi Desert, in which the first specimens were found, advanced embryos of Gobipteryx minuta were found.[8] Seven specimens in total were found, including two skeletons in the redbeds of Khermeen Tsav in Mongolia's Gobi Desert.[8] These embryos made up the second confirmed embryonic fossils from before the Quaternary Period as well as the first confirmed postcranial fossils of G. minuta found.[8]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 Elżanowski, A. (1974): Preliminary note on the Palaeognthous bird from the Upper Cretaceous of Mongolia Palaeontologia Polonica 30.
  2. ↑ Padian, K. (2004). "Basal Avialae". chptr 11, in Weishampel, D.B., Dodson, P. and Osmólska, H. (eds.): The Dinosauria 2nd Edition. University of California Press, Berkeley ISBN 978-0-520-25408-4.
  3. ↑ 3.0 3.1 3.2 3.3 Elżanowski, A. (1976): Palaeognathous bird from the Cretaceous of Central Asia Nature 264: 51-53. doi:10.1038/264051a0
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Chinsamy, A., Elżanowski, A. (2001): Bone histology: Evolution of growth pattern in birds Nature 412.
  5. ↑ Chatterjee, S. (1997): The Rise of Birds: 225 Million Years of Evolution The Johs Hopkins University Press ISBN 978-0801856150.
  6. ↑ 6.0 6.1 Elżanowski, A. (1977): Skulls of Gobipteryx (Aves) from the Upper Cretaceous of Mongolia Palaeontologia Polonica 37 p. 153-166.
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 Chiappe, Luis M.; Norell, Mark and Clark, James (2001): A New Skull of Gobipteryx minuta (Aves: Enantiornithes) from the Cretaceous of the Gobi Desert. American Museum Novitates 3346: 1–15.
  8. ↑ 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12 8.13 8.14 8.15 8.16 Elżanowski, A. (1981): Embryonic Bird Skeletons from the Late Cretaceous of Mongolia. Palaeontologica Polonica 42, 147-179.
  9. ↑ Walker, C. A. (1981): New subclass of birds from the Cretaceous of South America Nature 292 p. 51-53.
  10. ↑ Kurochkin, E. (1996): A new enantiornithid of the Mongolian Late Cretaceous, and the general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, Palaeontological Institute, Special Issue: 1-50.