Sapeornis
| Sapeornis Temporal range:Early Cretaceous,
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| Fossil specimen,National Museum of Natural Science | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | Avialae |
| Order: | †Omnivoropterygiformes |
| Family: | †Omnivoropterygidae |
| Genus: | †Sapeornis Zhou&Zhang,2002 |
| Species: | †S. chaoyangensis
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| Binomial name | |
| †Sapeornis chaoyangensis Zhou & Zhang, 2002
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| Synonyms | |
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Genus synonymy
Species synonymy
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Sapeornisis a monotypic genus ofavialandinosaurswhich lived during the earlyCretaceous period(late Barremianto earlyAptian,roughly 125-120mya).Sapeorniscontains only one species,Sapeornis chaoyangensis.
Description
[edit]
Sapeorniswas large for an early avialan, about 30–33 centimetres (0.98–1.08 ft) long in life, excluding the tail feathers.
The hand ofSapeorniswas far more derived than that ofArchaeopteryx.It had three fingers, the outer ones with two and the middle one with threephalanges,and a well-fusedcarpometacarpus.Its arms were about half again as long as the legs, suggesting a large wing area. On the other hand, its shoulder girdle was apparently ill-adapted to flapping flight and itsfurculawas unusual, with ahypocleidumsimilar to more advanced avialans but a general anatomy even more basal than inArchaeopteryx.[2]Thehumeruswas large and bore holes, apparently to save weight, as in theConfuciusornithidae.
The skull has a handful of teeth in the upper jawtip only.Sapeornishadgastraliabut no (or unossified)uncinate processes.The breastbone (sternum) was either absent or, more likely, made of cartilage rather than bone, as in more basal theropods.[3]Thepygostylewas rod-like as inConfuciusornisandNomingia,but like in the former there was no long bony tail anymore. While thetarsometatarsiwere more fused than inArchaeopteryx,thefibulawas long and reached the distal point of the tarsal joint, not reduced as in more modern birds (and some non-avian theropods likeAvimimus). The first toe pointed backwards. In specimenIVPPV12375, the stomach contained numerous smallgastroliths.Analysis of its skeletal bones suggest that it had anontogenyand slow growth likeArchaeopteryxand small carnivorous dinosaurs, rather than the explosively fast growth seen in modern birds.[4]
In absolute number of features shared with modern birds,S. chaoyangensisis about as derived asConfuciusornis.However, theapomorphieswere largely different fromConfuciusornis,and a character analysis demonstrates that these two were not closely related.[5]The tail plumage ofSapeornisconsisted of rectrices that formed a graded, fan-like structure. The reduced fingers suggest that it might have had analula.Not being well-adapted to flapping flight,Sapeornisprobably was a glider and/or soarer that preferred more open country compared to the Enantiornithes and predominantly woodland birds, although it was able to perch on branches. The small gastroliths, overall large size, and the inferred habitat indicate thatSapeorniswas most likely aherbivore,possibly eating plant seeds and fruits.[6]
Comparisons between thescleral ringsofSapeornisand modern birds and reptiles indicate that it may have beendiurnal,similar to most modern birds.[7]
Discovery and history
[edit]
Sapeornisis known from fossils found inJiufotang FormationandYixian Formationrocks in western Liaoning, China. These rocks formed during thelate Aptianthrough earlyAlbianepochs of the Cretaceous period, and are about 125-120 million years old. Several nearly complete skeletons have been found.[6]
The first known specimen (thetype specimen) ofSapeorniswas an incomplete skeleton dug up from Jiufotang Formation rocks in the area of Shangheshou, nearChaoyang Cityin Liaoning Province, China in the summer of 2000. It was discovered by a team from theInstitute of Vertebrate Paleontology and Paleoanthropology(IVPP), and was reported in 2002 by the scientists Zhonghe Zhou and Fucheng Zhang.[8]They chose the name in honor of SAPE, theSociety of Avian Paleontology and Evolution,which they combined with theAncient Greekwordόρνις(ornis), meaning "bird". The species namechaoyangensisisLatinfor "from Chaoyang".[9]Soon after this, two more, nearly complete specimens were discovered in the Dapingfang area, about 40 kilometres (25 mi) from the original fossil site. None of these first three specimens preserved traces of feathers, but based on the size of their skeletons alone, they were recognized as the largest early Cretaceous avialans known at the time.[9]
In 2008, Yuan named a new specimen related toSapeornisasDidactylornis jii.Yuan concluded thatDidactylornisdiffered fromSapeornisin the proportions of the foot and number of wing and foot bones.[10]However, the relevant portions of the specimen were badly crushed, and later authors concluded that these differences were based on misinterpretation of the poorly preserved specimen. In a 2010 survey of Chinese avialan fossils, Li and colleagues consideredDidactylornisa synonym ofSapeornis chaoyangensis.[11]In a 2012 study, Gaoet al.concluded thatDidactylorniswas indeed a junior synonym ofSapeornis chaoyangensis,as wereShenshiornisand the supposed second species ofSapeornis,S. angustis.[12]Omnivoropteryxis also likely synonymous withSapeornis.[13]
References
[edit]- ^Hu, D.; et al. (2010). "A new sapeornithid bird from China and its implication for early avian evolution".Acta Geologica Sinica.84(3): 472–482.Bibcode:2010AcGlS..84..472H.doi:10.1111/j.1755-6724.2010.00188.x.S2CID86441777.
- ^Senter, Phil (2006)."Scapular orientation in theropods and basal birds, and the origin of flapping flight"(PDF).Acta Palaeontologica Polonica.51(2): 305–313.
- ^Foth, C. (2014). Comment on the absence of ossified sternal elements in basal paravian dinosaurs.Proceedings of the National Academy of Sciences,111(50): E5334-E5334.doi:10.1073/pnas.1419023111
- ^Erickson, Gregory M.; Rauhut, Oliver W. M.; Zhou, Zhonghe; Turner, Alan H.; Inouye, Brian D.; Hu, Dongyu; Norell, Mark A. (2009)."Was Dinosaurian Physiology Inherited by Birds? Reconciling Slow Growth inArchaeopteryx".PLOS ONE.4(10): e7390.Bibcode:2009PLoSO...4.7390E.doi:10.1371/journal.pone.0007390.PMC2756958.PMID19816582.
- ^Zhou, Zhonghe; Zhang, Fucheng (2006). "A beaked basal ornithurine bird (Aves, Ornithurae) from the Lower Cretaceous of China".Zool. Scripta.35(4): 363–373.doi:10.1111/j.1463-6409.2006.00234.x.S2CID85222311.
- ^abZhou, Zhonghe & Zhang, Fucheng (2003): Anatomy of the primitive birdSapeornis chaoyangensisfrom the Early Cretaceous of Liaoning, China.Canadian Journal of Earth Sciences40(5): 731–747.doi:10.1139/E03-011(HTML abstract)
- ^Schmitz, L.; Motani, R. (2011). "Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology".Science.332(6030): 705–8.Bibcode:2011Sci...332..705S.doi:10.1126/science.1200043.PMID21493820.S2CID33253407.
- ^Zhou, Z.; Zhang, F. (2002). "Largest Bird from the Early Cretaceous and Its Implications for the Earliest Avian Ecological Diversification".Naturwissenschaften.89(1): 34–38.Bibcode:2002NW.....89...34Z.doi:10.1007/s00114-001-0276-9.PMID12008971.S2CID1116829.
- ^abZhou, Z., & Zhang, F. (2003). Anatomy of the primitive birdSapeornis chaoyangensisfrom the Early Cretaceous of Liaoning, China.Canadian Journal of Earth Sciences,40(5): 731-747.doi:10.1139/E03-011
- ^Yuan, C. (2008). "A new genus and species of Sapeornithidae from Lower Cretaceous in western Liaoning, China".Acta Geologica Sinica.82(1): 48–55.Bibcode:2008AcGlS..82...48Y.doi:10.1111/j.1755-6724.2008.tb00323.x.S2CID86691693.
- ^Li, D.; Sullivan, C.; Zhou, Z.; Zhang, Z. (2010). "Basal birds from China: a brief review".Chinese Birds.1(2): 83–96.doi:10.5122/cbirds.2010.0002.S2CID84976296.
- ^Gao, C.; Chiappe, L.M.; Zhang, F.; Pomeroy, D.L.; Shen, C.; Chinsamy, A.; Walsh, M.O. (2012). "A subadult specimen of the Early Cretaceous birdSapeornis chaoyangensisand a taxonomic reassessment of sapeornithids ".Journal of Vertebrate Paleontology.32(5): 1103–1112.Bibcode:2012JVPal..32.1103G.doi:10.1080/02724634.2012.693865.S2CID86195304.
- ^Holtz, Thomas R. Jr. (2011)Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,Winter 2010 Appendix.
