Aurornis
From Latin 'aurora' ('dawn', 'daybreak') and Greek 'ornis' ('bird'); meaning 'dawn bird'.
Aurornis is an extinct genus of anchiornithid theropod dinosaurs from the Jurassic Period of China. The genus Aurornis contains a single known species, Aurornis xui. Aurornis xui may be the most basal ("primitive") avialan dinosaur known to date, and it is one of the earliest avialans found to date. The fossil evidence for the animal pre-dates that of Archaeopteryx lithographica, often considered the earliest bird species, by about 10 million years.
Under dispute
Aurornis xui was erected from a complete articulated skeleton and recovered as the basal-most avialan, more basal than Archaeopteryx, with Troodontidae as the sister group of Avialae (Godefroit and colleagues, 2013). Its distinctness has since been challenged: Pei and colleagues (2017), followed by Agnolín and colleagues (2019), regard it as a junior synonym of Anchiornis huxleyi, citing the absence of unambiguous characters separating the two and noting that Aurornis rests on a single specimen from the same beds that have yielded more than two hundred specimens of Anchiornis. That synonymy has not been adopted: Pittman and colleagues (2020), Pei and colleagues (2020) and Xu and colleagues (2023) all continue to score Aurornis as a distinct terminal taxon, the last recovering it in an Anchiornithidae uniting Anchiornis, Aurornis, Xiaotingia and Eosinopteryx with their interrelationships unresolved. It is retained as a valid anchiornithid, and placed at Anchiornithidae rather than at the basal avialan position of the describing paper, which subsequent analyses have not upheld.
Diagnosis
- Manual phalanx I-1 distinctly more robust than the radius
- Robust postacetabular process of ilium not markedly deflected ventrally, with a horizontal dorsal margin
- Distal end of ischium dorsoventrally expanded, formed by a hook-like ventral process delimiting a prominent distal obturator notch and by a longer dorsal distal process
- Metatarsal I gracile and elongate, about 30% of metatarsal III length
Species
Aurornis xui Godefroit et al., 2013
Type species
Honors Xu Xing, for contributions to the understanding of feathered dinosaur evolution and biology.
- Holotype
- YFGP-T5198 , Yizhou Fossil and Geology Park
- Material
- Complete articulated skeleton with associated integumentary structures.
- Horizon
- Tiaojishan Formation, Callovian–Kimmeridgian, Middle Jurassic–Late Jurassic , 165.3–149.2 million years ago The age of the containing rock unit; no finer age has been published.
- Locality
- Yaolugou, Jianchang, Liaoning, China No finer age is published for the Yaolugou horizon, so the stages are the formation's. The Oxfordian that Lefèvre and colleagues (2017) give is for the formation at Daxishan, another locality.
References
-
Godefroit, P.; Cau, A.; Hu, D. Y.; Escuillié, F.; Wu, W.; Dyke, G. (2013). A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Nature 498(7454): 359-362. Springer Science and Business Media LLC. doi:10.1038/nature12168
Erects the genus and species and recovers it as the basal-most avialan, more basal than Archaeopteryx.
godefroit2013b -
Agnolín, F. L.; Motta, M. J.; Brissón Egli, F.; Lo Coco, G.; Novas, F. E. (2019). Paravian Phylogeny and the Dinosaur-Bird Transition: An Overview. Frontiers in Earth Science 6: 252. doi:10.3389/feart.2018.00252
Considers Aurornis xui a junior synonym of Anchiornis huxleyi, following Pei and colleagues (2017), on the absence of unambiguous distinguishing characters.
agnolín2019a -
Pittman, M.; O'Connor, J.; Field, D. J.; Turner, A. H.; Ma, W.; Makovicky, P.; Xu, X. (2020). Pennaraptoran systematics. Pennaraptoran Theropod Dinosaurs: Past Progress and New Frontiers (Pittman, M.; Xu, X., eds.) 440: 7-36. American Museum of Natural History, New York.
Gathers Anchiornis, Aurornis, Eosinopteryx and Xiaotingia into a distinct clade of early-branching avialans.
pittman2020b -
Pei, R.; Pittman, M.; Goloboff, P. A.; Dececchi, T. A.; Habib, M. B.; Kaye, T. G.; Larsson, H. C. E.; Norell, M. A.; Brusatte, S. L.; Xu, X. (2020). Potential for Powered Flight Neared by Most Close Avialan Relatives, but Few Crossed Its Thresholds. Current Biology 30(20): 4033-4046.e8. Elsevier BV. doi:10.1016/j.cub.2020.06.105
Scores Aurornis as a separate terminal and recovers the anchiornithine paravians as the earliest-diverging avialan clade.
pei2020a -
Xu, L.; Wang, M.; Chen, R.; Dong, L.; Lin, M.; Xu, X.; Tang, J.; You, H.; Zhou, G.; Wang, L.; He, W.; Li, Y.; Zhang, C.; Zhou, Z. (2023). A new avialan theropod from an emerging Jurassic terrestrial fauna. Nature 621(7978): 336-343. Springer Science and Business Media LLC. doi:10.1038/s41586-023-06513-7
Recovers an Anchiornithidae uniting Anchiornis, Aurornis, Xiaotingia and Eosinopteryx, with their interrelationships unresolved.
xu2023a -
Hu, D.; Clarke, J. A.; Eliason, C. M.; Qiu, R.; Li, Q.; Shawkey, M. D.; Zhao, C.; D'Alba, L.; Jiang, J.; Xu, X. (2018). A bony-crested Jurassic dinosaur with evidence of iridescent plumage highlights complexity in early paravian evolution. Nature Communications 9(1). Springer Science and Business Media LLC. doi:10.1038/s41467-017-02515-y
Distinguishes Caihong juji from Aurornis xui and the other Yanliao paravians, and reports the integument.
hu2018a -
Lefèvre, U.; Cau, A.; Cincotta, A.; Hu, D.; Chinsamy, A.; Escuillié, F.; Godefroit, P. (2017). A new Jurassic theropod from China documents a transitional step in the macrostructure of feathers. The Science of Nature 104(9-10). Springer Science and Business Media LLC. doi:10.1007/s00114-017-1496-y
Source of the Oxfordian dating of the Tiaojishan Formation, and comparative caudal counts.
lefèvre2017a - Pei, R.; Li, Q.; Meng, Q.; Norell, M. A.; Gao, K. Q. (2017). New specimens of Anchiornis huxleyi (Theropoda: Paraves) from the Late Jurassic of northeastern China. Bulletin of the American Museum of Natural History (411): 1-67. American Museum of Natural History. doi:10.1206/0003-0090-411.1.1 pei2017b