Protopteryx

Protopteryx
Temporal range: Early Cretaceous, 131 Ma
↓
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Clade: †Enantiornithes
Order: †Protopterygiformes
Zhang & Zhou, 2006
Family: †Protopterygidae
Zhang & Zhou, 2006
Genus: †Protopteryx
Zhang & Zhou, 2000
Species: †P. fengningensis
Binomial name
Protopteryx fengningensis
Zhang & Zhou, 2000

Protopteryx is an extinct genus of bird and the most primitive enantiornithine, from the Cretaceous period.[1] The type species is P. fengningensis.[2] It was first discovered in the Sichakou Member of the Yixian Formation of Hebei Province, northern China,[3] dating from 131 Ma ago.[4] Protopteryx has been found in the Daibeigou formation, as well.[5] The name Protopteryx means "primitive feather":[6] "proto-" meaning "the first of" and "-pteryx" meaning "feather" or "wing." The name comes from the fact that Protopteryx feathers have features of modern ones as well as of reptilian scales, such as the two elongated tail feathers that lack barbs and rami.[7]

Description

Protopteryx fossils show that they were roughly the same as a today's starling.[6] The adult body length of the Protopteryx was about 10 centimetres (3.9 in), excluding the tail feathers. Protopteryx teeth were conical and unserrated, and some teeth had a resorption pit similar to those seen in Archaeopteryx. The body of the Protopteryx was covered in three types of feathers: down feathers, flight feathers, and long, ribbon-like tail feathers. The body was mostly covered in feathers of about 12 millimetres (0.47 in). The barbs of the down feathers were laminar instead of hairlike and were frayed at the tips. The most distinctive feature of the Protopteryx is that the tail consisted of two long feathers which only had barbs at their tips. Closer to the body, the long tail feathers were thin and needle-like. The only modern birds to share a feather type similar to the Protopteryx is the red bird-of-paradise. The tail feathers also lack rami on the proximal end of the tail.[8]

Classification

Protopteryx is one of the most primitive known members of the group Enantiornithes. It appeared after Archaeopteryx, one of the most primitive birds, and Confuciusornis.[9] Protopteryx is related to, but is more primitive than, the species Eocathayornis,[1] Paraprotopteryx,[10] and Confuciusornis[11]

Discovery and geography

Protopteryx was discovered in the Sichakou Member of the Hebei province, west of the Liaoning province.[12] The formations where Protopteryx was found were the Yixian and Dageibou formations.[13][14] The Sichakou Basin is part of the Daxinganling-Taihangshan Tectonomagmatic Belt and moves in a north-northeast direction. When Protopteryx was alive, the Sichakou basin was located at the Hongqiangou-Jiecangou.[12]

Paleobiology

Protopteryx lived in the Jehol Biota in the Cretaceous period, which contains many of the terrestrial and freshwater vertebrate clades.[15] The teeth of the Protopteryx are similar to Archaeopteryx, suggesting a similar diet.[8]

Adaptions of feathers

Protopteryx was adapted for flying and had feathers with features similar to modern birds, as shown by their procoracoid, carina of the sternum, external tuberosity of the humerus, and deltoid crest. These features suggest Protopteryx had modern musculus supercoracoideus and pectoralis. Protopteryx also share asymmetric wing flight feathers with flying birds, as well as Archaeopteryx and Confuciusornis.[8] Tail feathers of Protopteryx have different features to their other feathers: lack of barbs and rami close to the body.[8] The lack of barbs suggests the feathers have a use outside of flight, such as display, thermoregulation, or sensory usage.[9]

Evolution of feathers

Feather evolution is believed to have evolved by: elongation of scales, development of central shaft or rachis, differentiation of vanes into barbs, and appearance of barbules and barbicels. Protopteryx fossils show that feathers evolved with aerodynamics first before being adapted for other reasons. However protofeathers in theropod dinosaurs have indicated that feathers were first used in thermoregulation and displays with flight in birds being an exadaptation. The dinosaur endothermic hypothesis, however, has no support for endothermy in early birds.[7] The different type of the tail feathers seen in Protopteryx suggests a specialization of ancestral feathers, evolved after the common type of feather seen in Archaeopteryx.[8] The origin of avian feathers is being researched and still debated.[7]

References

  1. 1 2 Zhou, Zhonghe. (2002). "A new and primitive enantiornithine bird from the Early Cretaceous of China." Journal of Vertebrate Paleontology, 22(1): 49-57.
  2. ↑ Zhang, Fucheng; Zhou, Zhonghe (2000). "A Primitive Enantiornithine Bird and the Origin of Feathers". Science. 290 (5498): 1955–1959. Bibcode:2000Sci...290.1955Z. doi:10.1126/science.290.5498.1955. PMID 11110660.
  3. ↑ Jin, F.; Zhang, F.C.; Li, Z.H.; Zhang, J.Y.; Li, C.; Zhou, Z.H. (2008). "On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota". Chinese Science Bulletin. 53 (18): 2820–2827. doi:10.1007/s11434-008-0209-5.
  4. ↑ O'Connor, J.K., Zhou Z. and Zhang F. (In press). "A reappraisal of Boluochia zhengi (Aves: Enantiornithes) and a discussion of intraclade diversity in the Jehol avifauna, China." Journal of Systematic Palaeontology, (published online before print 16 December 2010). doi:10.1080/14772019.2010.512614
  5. ↑ Zhiheng Li, Zhonghe Zhou, Min Wang, Julia A. Clarke, (2014). "A New Specimen of Large-Bodied Basal Enantiornithine Bohaiornis from the Early Cretaceous of China and the Inference of Feeding Ecology in Mesozoic Birds." Journal of Paleontology, 88: 99-108.
  6. 1 2 A Primitive Enantiornithine Bird and the Origin of Feathers Fucheng Zhang and Zhonghe Zhou Science 8 December 2000: 290 (5498), 1955-1959. [DOI:10.1126/science.290.5498.1955]
  7. 1 2 3 Zhou, Zhonghe, and Fucheng Zhang. "Origin of feathers–perspectives from fossil evidence." Science Progress 84, no. 2 (2001): 87-104.
  8. 1 2 3 4 5 "A Primitive Enantiornithine Bird and the Origin of Feathers Fucheng Zhang and Zhonghe Zhou". Science 8 December 2000: 290 (5498), 1955-1959. [DOI:10.1126/science.290.5498.1955]
  9. 1 2 Fucheng, Z., Zhonghe, Z. and Dyke, G. (2006), Feathers and ‘feather-like’ integumentary structures in Liaoning birds and dinosaurs. Geol. J., 41: 395–404. doi: 10.1002/gj.1057
  10. ↑ Xiaoting, Z., Zihui, Z. and Lianhai, H. (2007), A New Enantiornitine Bird with Four Long Rectrices from the Early Cretaceous of Northern Hebei, China. Acta Geologica Sinica, 81: 703–708. doi: 10.1111/j.1755-6724.2007.tb00995.x
  11. ↑ Early Adaptive Radiation of Birds: Evidence from Fossils from Northeastern China Lianhai Hou, Larry D. Martin, Zhonghe Zhou, and Alan Feduccia Science 15 November 1996: 274 (5290), 1164-1167. [DOI:10.1126/science.274.5290.1164]
  12. 1 2 Jin, F.; Zhang, F.C.; Li, Z.H.; Zhang, J.Y.; Li, C.; Zhou, Z.H. (2008). "On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota". Chinese Science Bulletin 53 (18): 2820–2827. doi:10.1007/s11434-008-0209-5.
  13. ↑ Zhonghe, Z. (2006), "Evolutionary radiation of the Jehol Biota: chronological and ecological perspectives". Geol. J., 41: 377–393. doi: 10.1002/gj.1045
  14. ↑ O’Connor, Jingmai K., Zhonghe Zhou, and Fucheng Zhang. "A reappraisal of Boluochia zhengi (Aves: Enantiornithes) and a discussion of intraclade diversity in the Jehol avifauna, China." Journal of Systematic Palaeontology 9, no. 1 (2011): 51-63.
  15. ↑ He, H. Y., X. L. Wang, F. Jin, Z. H. Zhou, F. Wang, L. K. Yang, X. Ding, A. Boven, and R. X. Zhu (2006), "The 40Ar/39Ar dating of the early Jehol Biota from Fengning, Hebei Province, northern China", Geochem. Geophys. Geosyst., 7, Q04001, doi:10.1029/2005GC001083.

Sources

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