Lloyd, G. T., Bapst, D. W., Friedman, M. & Davis, K. E. Probabilistic divergence time estimation without branch lengths: dating the origins of dinosaurs, avian flight and crown birds. Biol. Lett. 12, 20160609 (2016).
Benson, R. B. J. et al. Rates of dinosaur body mass evolution indicate 170 million years of sustained ecological innovation on the avian stem lineage. PLOS Biol. 12, e1001853 (2014).
Brusatte, S. L., O’Connor, J. K. & Jarvis, E. D. The origin and diversification of birds. Curr. Biol. 25, R888–R898 (2015).
Rauhut, O. W. M. & Foth, C. in The Evolution of Feathers: From Their Origin to the Present (eds Foth, C. & Rauhut, O. W. M.) 27–45 (Springer International Publishing, 2020).
Chen, R. et al. Earliest short-tailed bird from the Late Jurassic of China. Nature 638, 441–448 (2025).
Xu, X. et al. An integrative approach to understanding bird origins. Science 346, 1253293 (2014).
Pei, R. et al. Potential for powered flight neared by most close avialan relatives, but few crossed its thresholds. Curr. Biol. 30, 4033–4046 (2020).
Sullivan, C., Xu, X. & O’Connor, J. K. Complexities and novelties in the early evolution of avian flight, as seen in the Mesozoic Yanliao and Jehol Biotas of Northeast China. Palaeoworld 26, 212–229 (2017).
Xu, L. et al. A new avialan theropod from an emerging Jurassic terrestrial fauna. Nature 621, 336–343 (2023).
Wang, M. et al. Jurassic avialan reveals stepwise evolution of bony tail in birds. Sci. Adv. 12, eaeb5202 (2016).
Makovicky, P. J. & Norell, M. A. in The Dinosauria (eds Weishampel, D. et al.) 184–195 (Univ. California Press, 2004).
Wang, M., Wang, X., Zheng, X. & Zhou, Z. Cranial anatomy of Anchiornis huxleyi (Theropoda: Paraves) sheds new light on bird skull evolution. Vertebr. Palasiat. 63, 20–42 (2025).
Rauhut, O. W., Foth, C. & Tischlinger, H. The oldest Archaeopteryx (Theropoda: Avialiae): a new specimen from the Kimmeridgian/Tithonian boundary of Schamhaupten, Bavaria. PeerJ 6, e4191 (2018).
Wang, M., Stidham, T. A., Li, Z., Xu, X. & Zhou, Z. Cretaceous bird with dinosaur skull sheds light on avian cranial evolution. Nat. Commun. 12, 3890 (2021).
O’Connor, J. K. & Chiappe, L. M. A revision of enantiornithine (Aves: Ornithothoraces) skull morphology. J. Syst. Palaeontol. 9, 135–157 (2011).
Turner, A. H., Makovicky, P. J. & Norell, M. A. A review of dromaeosaurid systematics and paravian phylogeny. Bull. Am. Mus. Nat. Hist. 371, 1–206 (2012).
Xu, X. & Wu, X. Cranial morphology of Sinornithosaurus millenii Xu et al. 1999 (Dinosauria: Theropoda: Dromaeosauridae) from the Yixian Formation of Liaoning, China. Can. J. Earth Sci. 38, 1739–1752 (2001).
Xu, X. et al. The taxonomic status of the Late Cretaceous dromaeosaurid Linheraptor exquisitus and its implications for dromaeosaurid systematics. Vertebr. Palasiat. 53, 29–62 (2015).
Hu, D. et al. A bony-crested Jurassic dinosaur with evidence of iridescent plumage highlights complexity in early paravian evolution. Nat. Commun. 9, 217 (2018).
O’Connor, J. K. et al. Chicago Archaeopteryx informs on the early evolution of the avian bauplan. Nature 641, 1201–1207 (2025).
Currie, P. J. Bird-like characteristics of the jaws and teeth of troodontid theropods (Dinosauria, Saurischia). J. Vertebr. Paleontol. 7, 72–81 (1987).
Xu, X., Norell, M. A., Wang, X., Makovicky, P. J. & Wu, X. A basal troodontid from the Early Cretaceous of China. Nature 415, 780–784 (2002).
Pei, R., Li, Q., Meng, Q., Norell, M. A. & Gao, K. New specimens of Anchiornis huxleyi (Theropoda: Paraves) from the Late Jurassic of northeastern China. Bull. Amer. Mus. Nat. Hist. 411, 1–67 (2017).
Xu, X. et al. Mosaic evolution in an asymmetrically feathered troodontid dinosaur with transitional features. Nat. Commun. 8, 14972 (2017).
Li, Z. et al. Ultramicrostructural reductions in teeth: implications for dietary transition from non-avian dinosaurs to birds. BMC Evol. Biol. 20, 46 (2020).
Norell, M. A. & Makovicky, P. J. in The Dinosauria (eds Weishampel, D. et al.) 196–209 (Univ. California Press, 2004).
Dumont, M. et al. Synchrotron imaging of dentition provides insights into the biology of Hesperornis and Ichthyornis, the ‘last’ toothed birds. BMC Evol. Biol. 16, 178 (2016).
Hu, H. et al. Cranial osteology and palaeobiology of the Early Cretaceous bird Jeholornis prima (Aves: Jeholornithiformes). Zool. J. Linn. Soc. 198, 93–112 (2022).
Barsbold, R. & Osmólska, H. The skull of Velociraptor (Theropoda) from the late Cretaceous of Mongolia. Acta Palaeontol. Polonica 44, 189–219 (1999).
Yin, Y., Pei, R. & Zhou, C. Cranial morphology of Sinovenator changii (Theropoda: Troodontidae) on the new material from the Yixian Formation of western Liaoning, China. PeerJ 6, e4977 (2018).
Elżanowski, A. & Wellnhofer, P. Cranial morphology of Archaeopteryx: evidence from the seventh skeleton. J. Vertebr. Paleontol. 16, 81–94 (1996).
Sullivan, C. & Xu, X. Morphological diversity and evolution of the jugal in dinosaurs. Anat. Rec. 300, 30–48 (2017).
Xu, X., You, H., Du, K. & Han, F. An Archaeopteryx-like theropod from China and the origin of Avialae. Nature 475, 465–470 (2011).
Li, Z., Wang, M., Stidham, T. A. & Zhou, Z. Decoupling the skull and skeleton in a Cretaceous bird with unique appendicular morphologies. Nat. Ecol. Evol. 7, 20–31 (2023).
Wang, M. & Hu, H. A comparative morphological study of the jugal and quadratojugal in early birds and their dinosaurian relatives. Anat. Rec. 300, 62–75 (2017).
Ostrom, J. H. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Bull. Peabody Mus. Nat. Hist. 30, 1–165 (1969).
Chiappe, L. M. & Meng, Q. Birds of Stone: Chinese Avian Fossils from the Age of Dinosaurs (Johns Hopkins Univ. Press, 2016).
Novas, F. E. et al. Comments on the morphology of basal paravian shoulder girdle: new data based on unenlagiid theropods and paleognath birds. Front. Earth Sci. 9, 662167 (2021).
Zhang, C. Selecting and averaging relaxed clock models in Bayesian tip dating of Mesozoic birds. Paleobiology 48, 340–352 (2022).
Wang, M. & Zhou, Z. Low morphological disparity and decelerated rate of limb size evolution close to the origin of birds. Nat. Ecol. Evol. 2, 1257–1266 (2023).
Chiappe, L. M. in Mesozoic Birds: Above the Heads of Dinosaurs (eds Chiappe L. M. & Witmer L. M.) 281–316 (Univ. California Press, 2002).
Mayr, G., Pohl, B., Hartman, S. & Peters, D. S. The tenth skeletal specimen of Archaeopteryx. Zool. J. Linn. Soc. 149, 97–116 (2007).
Hwang, S. H., Norell, M. A., Qiang, J. I. & Keqin, G. A. O. New Specimens of Microraptor zhaoianus (Theropoda: Dromaeosauridae) from Northeastern China. Am. Mus. Novit. 3381, 1–44 (2002).
Xu, X. et al. A new feathered maniraptoran dinosaur fossil that fills a morphological gap in avian origin. Chin. Sci. Bull. 54, 430–435 (2009).
Agnolin, F. L., Motta, M. J., Brissón Egli, F., Lo Coco, G. & Novas, F. E. Paravian phylogeny and the dinosaur-bird transition: an overview. Front. Earth Sci. 6, 252 (2019).
Hutchinson, J. R. The evolution of pelvic osteology and soft tissues on the line to extant birds (Neornithes). Zool. J. Linn. Soc. 131, 123–168 (2001).
Forster, C. A., Sampson, S. D., Chiappe, L. M. & Krause, D. W. The theropod ancestry of birds: new evidence from the Late Cretaceous of Madagascar. Science 279, 1915–1919 (1998).
Botelho, J. F. et al. Molecular development of fibular reduction in birds and its evolution from dinosaurs. Evolution 70, 543–554 (2016).
Botelho, J. F. et al. Greater growth of proximal metatarsals in bird embryos and the evolution of hallux position in the grasping foot. J. Exp. Zool. 328, 106–118 (2017).
Xu, X. & Wang, X. L. Troodontid-like pes in the dromaeosaurid Sinornithosaurus. Paleont. Soc. Korea Spec. Publ. 4, 179–188 (2000).
Zanno, L. E., Varricchio, D. J., O’Connor, P. M., Titus, A. L. & Knell, M. J. A new troodontid theropod, Talos sampsoni gen. et sp. nov., from the Upper Cretaceous western interior basin of North America. PLOS ONE 6, e24487 (2011).
O’Connor, J. K. A Systematic Review of Enantiornithes (Aves: Ornithothoraces) (Univ. Southern California, 2009).
Zhou, Z. & Zhang, F. Two new ornithurine birds from the Early Cretaceous of western Liaoning, China. Chin. Sci. Bull. 46, 1258–1264 (2001).
Zhang, F., Zhou, Z., Hou, L. & Gu, G. Early diversification of birds: evidence from a new opposite bird. Chin. Sci. Bull. 46, 945–949 (2001).
Manning, P. L., Payne, D., Pennicott, J., Barrett, P. M. & Ennos, R. A. Dinosaur killer claws or climbing crampons?. Biol. Lett. 2, 110–112 (2006).
Novas, F. E. & Pol, D. New evidence on deinonychosaurian dinosaurs from the Late Cretaceous of Patagonia. Nature 433, 858–861 (2005).
Middleton, K. M. & Gatesy, S. M. Theropod forelimb design and evolution. Zool. J. Linn. Soc. 128, 149–187 (2000).
Dececchi, T. A. & Larsson, H. C. E. Body and limb size dissociation at the origin of birds: uncoupling allometric constraints across a macroevolutionary transition. Evolution 67, 2741–2752 (2013).
Motta, M. J., Brissón Egli, F. & Novas, F. E. Tail anatomy of Buitreraptor gonzalezorum (Theropoda, Unenlagiidae) and comparisons with other basal paravians. Cretac. Res. 83, 168–181 (2018).
Foth, C. & Rauhut, O. W. M. Re-evaluation of the Haarlem Archaeopteryx and the radiation of maniraptoran theropod dinosaurs. BMC Evol. Biol. 17, 236 (2017).
Gianechini, F. A., Makovicky, P. J., Apesteguía, S. & Cerda, I. Postcranial skeletal anatomy of the holotype and referred specimens of Buitreraptor gonzalezorum Makovicky, Apesteguía and Agnolín 2005 (Theropoda, Dromaeosauridae), from the Late Cretaceous of Patagonia. PeerJ 6, e4558 (2018).
Hu, D., Hou, L., Zhang, L. & Xu, X. A pre-Archaeopteryx troodontid theropod from China with long feathers on the metatarsus. Nature 461, 640–643 (2009).
Field, D. J. et al. Complete Ichthyornis skull illuminates mosaic assembly of the avian head. Nature 557, 96–100 (2018).
Clarke, J. A. & Middleton, K. M. Mosaicism, modules, and the evolution of birds: results from a Bayesian approach to the study of morphological evolution using discrete character data. Syst. Biol. 57, 185–201 (2008).
Francillon-Vieillot, H. et al. in Skeletal Biomineralization: Patterns, Processes and Evolutionary Trends Vol. 1 (ed. Carter J. G.) 175–234 (American Geophysical Union, 1990).
Brusatte, S. L., Lloyd, G. T., Wang, S. C. & Norell, M. A. Gradual assembly of avian body plan culminated in rapid rates of evolution across the dinosaur–bird transition. Curr. Biol. 24, 2386–2392 (2014).
Turner, A. H., Montanari, S. & Norell, M. A. A new dromaeosaurid from the Late Cretaceous Khulsan locality of Mongolia. Am. Mus. Novit. 2020, 3965 (2021).
Goloboff, P. A. & Catalano, S. A. TNT version 1.5, including a full implementation of phylogenetic morphometrics. Cladistics 32, 221–238 (2016).
Ezcurra, M. D. Exploring the effects of weighting against homoplasy in genealogies of palaeontological phylogenetic matrices. Cladistics 40, 242–281 (2024).
Ronquist, F. et al. MrBayes 3.2: efficient Bayesian phylogenetic inference and model choice across a large model space. Syst. Biol. 61, 539–542 (2012).
Yang, Z. Maximum likelihood phylogenetic estimation from DNA sequences with variable rates over sites: approximate methods. J. Mol. Evol. 39, 306–314 (1994).
Zhang, C., Stadler, T., Klopfstein, S., Heath, T. A. & Ronquist, F. Total-evidence dating under the fossilized birth–death process. Syst. Biol. 65, 228–249 (2015).
Bell, A. & Chiappe, L. M. Statistical approach for inferring ecology of Mesozoic birds. J. Syst. Palaeontol. 9, 119–133 (2011).
Gatesy, S. M. Hind limb scaling in birds and other theropods: implications for terrestrial locomotion. J. Morphol. 209, 83–96 (1991).
Gatesy, S. M. & Middleton, K. M. Bipedalism, flight, and the evolution of theropod locomotor diversity. J. Vertebr. Paleontol. 17, 308–329 (1997).
Brusatte, S. L. in Computational Paleontology (ed. Elewa A. M. T.) 53–74 (Springer-Verlag, 2011).
Revell, L. J. phytools 2.0: an updated R ecosystem for phylogenetic comparative methods (and other things). PeerJ 12, e16505 (2024).
Rohlf, F. TpsDig2. v.2.1 https://tpsdig2.software.informer.com (2009).
Zelditch, M. L., Swiderski, D. L. & Sheets, H. D. Geometric Morphometrics for Biologists: a Primer (Academic, 2012).
Adams, D. C. & Otárola-Castillo, E. geomorph: an R package for the collection and analysis of geometric morphometric shape data. Methods Ecol. Evol. 4, 393–399 (2013).
Stefan, S. Morpho: calculations and visualisations related to geometric morphometrics, version 2.13. https://cran.r-project.org/web/packages/Morpho/Morpho.pdf (2026).
Palci, A., Hutchinson, M. N., Caldwell, M. W. & Lee, M. S. The morphology of the inner ear of squamate reptiles and its bearing on the origin of snakes. R. Soc. Open Sci. 4, 170685 (2017).
Xu, L. et al. Jurassic flightless bird reveals early ecological diversity of avialans. figshare https://doi.org/10.6084/m9.figshare.31228414 (2026).
