True Birds Evolved Before the K-Pg Extinction, Independent of Feathered Dinosaurs

By Lewis Loflin | Published May 17, 2025

Popular media frequently asserts that birds evolved from feathered dinosaurs, such as Archaeopteryx, and are often described as “living dinosaurs.” This perspective is misleading. True birds, characterized by toothless, keratinous beaks, emerged approximately 80 million years ago (Ma) during the Late Cretaceous, well before the K-Pg extinction event at 66 Ma that marked the extinction of most dinosaurs, including toothy theropods. Fossil evidence indicates that true birds, rather than feathered theropods with teeth, are the likely ancestors of modern birds. The notion of a direct bird-dinosaur connection oversimplifies evolutionary relationships, and feathered reptiles are not necessary to explain avian origins. This analysis aims to dispel simplified, often inaccurate wording that distorts the complex conditions surrounding these events, provoke thought, and present alternate viewpoints grounded in physical evidence. Inspired by Robert Bakker’s rigorous approach, this discussion offers a critical perspective on bird evolution and the post-K-Pg environment.

Definitions of Key Terms

For clarity, the following terms are defined as used in this discussion:

True Bird: An organism with a toothless, keratinous beak, as seen in modern birds (e.g., sparrows, ostriches). Example: Hesperornis (~80 Ma).
Proto-Bird: A transitional form with feathers and some avian characteristics but retaining teeth and dinosaurian traits, such as Archaeopteryx (150 Ma) or Ichthyornis (95–85 Ma).
Feathered Reptile: Theropod dinosaurs with feathers, such as Archaeopteryx or Microraptor, often inaccurately labeled as birds.
K-Pg Boundary: The mass extinction event at 66 Ma that led to the extinction of most dinosaurs and toothy theropods, after which modern birds with toothless beaks (Neornithes) are observed in the fossil record.
Neornithes: The clade encompassing all modern birds, characterized by toothless beaks, including Vegavis (~66 Ma).

Emergence of True Birds Before the K-Pg Extinction

True birds, defined by their toothless beaks, are distinct from dinosaurs and proto-birds with teeth. Fossil evidence demonstrates their emergence approximately 80 Ma, coexisting with dinosaurs such as Tyrannosaurus rex during the Late Cretaceous:

Hesperornis (~80 Ma): Fossils from North America reveal a toothless, keratinous beak and a diving lifestyle, analogous to modern loons. It is classified within or near Neornithes, qualifying as a true bird (Marsh, 1880).
Ichthyornis (95–85 Ma): Fossils indicate a beak with small, vestigial teeth in some specimens, positioning it as a proto-bird. The near-toothless condition suggests a transitional phase toward true birds like Hesperornis (Field et al., 2018).
Vegavis (~66 Ma): Fossils from Antarctica confirm a toothless, duck-like bird, solidifying Neornithes’ presence by the K-Pg boundary. However, this does not prove a direct descent from toothy theropods (Clarke et al., 2005).

The 15–30 million-year period from 95 to 80 Ma facilitated the transition from small, vestigial teeth to fully toothless beaks, as evidenced by the progression from Ichthyornis to Hesperornis. True birds, unlike scaly, toothy dinosaurs such as Triceratops, represent a distinct evolutionary lineage.

Feathered Reptiles as Unlikely Ancestors

Popular narratives often portray feathered reptiles like Archaeopteryx as direct bird ancestors. Fossil evidence suggests these theropods are more likely evolutionary dead ends:

Archaeopteryx (150 Ma): Known from 14 specimens, including the recently described Chicago Archaeopteryx, it exhibits feathers, flight-like tertial feathers, toothy jaws, a long bony tail, and scaled feet indicating ground-dwelling habits. Its temporal distance—84 Ma from the K-Pg boundary—and lack of clear linkage to true birds undermine its ancestral role (Bakker, 1986; O’Connor et al., 2025).
Velociraptor (75 Ma): Fossils from Mongolia reveal quill knobs on the ulna, indicating pennaceous feathers, likely for display or insulation, not flight. As a toothy, terrestrial predator, it lacks avian traits like a beak (Turner et al., 2007).
Enantiornithes (e.g., Avisaurus, ~70 Ma): Fossils from North America show asymmetrical feathers and teeth, indicating flight capability but not true bird status due to retained teeth. These proto-birds went extinct at the K-Pg boundary (Longrich et al., 2011).
Confuciusornis (125 Ma): Liaoning fossils reveal small teeth and feathers, classifying it as a proto-bird rather than a true bird.
Other feathered theropods, such as Microraptor, possessed feathers but lack evidence of direct descent to birds, suggesting Archaeopteryx’s lineage may have gone extinct.

The physiology of feathered theropods, particularly whether they were warm-blooded, remains debated. Evidence such as rapid growth rates and feathers for insulation suggests a high metabolism, potentially indicating endothermy (Erickson et al., 2009; Xu et al., 2012). However, some studies propose an intermediate metabolism, and the absence of definitive markers leaves this question unresolved (Amiot et al., 2011). Regardless, warm-bloodedness does not equate to bird ancestry, as true birds are defined by their toothless beaks, a trait absent in these theropods.

Feathered reptiles are not essential to avian origins. Hesperornis and numerous unknown ancestors, obscured by the scarcity of fossils, are more plausible candidates for modern bird ancestry.

Illustration of Archaeopteryx, a feathered theropod with toothy jaws and a long bony tail, from 150 million years ago

Archaeopteryx: Proof of evolutionary rigor lost in DEI-driven science education.

Creature	Traits	Time (Ma)
Archaeopteryx	Feathers, teeth, dinosaur-like	150
Ichthyornis	Beak, small teeth, bird-like	95–85
Hesperornis	Toothless beak, diving bird	80
Vegavis	Toothless beak, duck-like	66

Post-K-Pg Environment and Survival Patterns

The K-Pg extinction event at 66 Ma, triggered by the Chicxulub impact, transformed the global environment. Dust, soot, and sulfates blocked up to 90% of sunlight for 6–12 months, halting photosynthesis and causing an “impact winter” with 10–20°C cooling (Robertson et al., 2013; Vellekoop et al., 2014).

This darkness, comparable to the 6-month polar night in modern Arctic regions, allowed adapted species to survive through dormancy, scavenging, or low energy needs (Billings, 1987). Wildfires, sparked by re-entering ejecta, produced soot that worsened the darkness but varied by region—humid tropical wetlands saw fewer fires (Kaiho et al., 2016).

Heavy rainstorms, driven by sulfate aerosols, doused flames and washed soot from the atmosphere, speeding sunlight recovery in some areas (Schulte et al., 2010). Acid rain from vaporized sulfur, with a pH of 2.0–4.0 for months, lowered ocean and soil pH, with surface ocean pH dropping by ~0.2–0.3 units (Pierazzo et al., 2003; Henehan et al., 2019).

Deep oceans were less affected due to buffering, and coastal refugia or deep-sea vents saw milder changes (Schulte et al., 2010). On land, a “fern spike” and paleosols show soil pH temporarily dropped to 4.0–5.0 in non-carbonate regions, though ferns adapted well (Vajda & McLoughlin, 2004).

Carbonate rocks in some areas neutralized acid rain, raising pH faster, while silicate-rich regions faced longer effects (Pierazzo et al., 2010). Acid rain leached nutrients like calcium and potassium from soils but also mobilized toxic metals like aluminum and nickel, stressing ecosystems (Schulte et al., 2010).

Equatorial areas, deep oceans, and geothermal springs experienced less severe darkness and cold, serving as refugia for small species (Schulte et al., 2010). Despite the harsh conditions, small reptiles (e.g., lizards, turtles, crocodilians), amphibians (e.g., frogs, salamanders), mammals (e.g., proto-primates), and true birds like Vegavis survived (Longrich et al., 2012; Markwick, 1998).

Their survival hinged on small size, low energy needs, burrowing or aquatic habits, and dietary flexibility, such as scavenging or omnivory (Schulte et al., 2010). Toothy proto-birds like Enantiornithes and Ichthyornis went extinct, unable to adapt to the collapsed ecosystem.

The survival of diverse small species shows post-impact survival was driven by ecological adaptability, not a single lineage. This challenges the idea that true birds emerged directly from dinosaurs (Longrich et al., 2012).

Earth’s Resilience and Rapid Recovery

The K-Pg extinction, though catastrophic, underscores Earth’s resilience. Diverse species, including fish, insects, plants, reptiles, amphibians, mammals, and true birds, survived in less severe refugia (Schulte et al., 2010).

Recovery began within a year as atmospheric particulates settled and sunlight returned. Marine productivity resumed within ~1 year, as shown by carbon isotope records (D’Hondt et al., 1998).

On land, ferns and pioneer plants recolonized within months, with angiosperms recovering in 1–2 years (Vajda & McLoughlin, 2004). Opportunistic marine species like diatoms proliferated, and small vertebrates began rebounding soon after (Alegret et al., 2012; Wilson, 2014).

This rapid recovery highlights the planet’s ability to rebound from extreme disruptions. It supports the view that survival and recovery depended on ecological adaptability, not a specific lineage (Schulte et al., 2010).

Conclusion

The assertion that birds are direct descendants of dinosaurs is misleading. True birds, characterized by toothless beaks, emerged approximately 80 Ma with Hesperornis, prior to the K-Pg extinction, independent of feathered dinosaurs like Archaeopteryx. The scarcity of fossils likely conceals numerous beaked ancestors, rendering toothy theropods unnecessary for explaining avian origins. Analogous to how platypuses are not reptiles despite egg-laying, or T. rex is not a bird despite being a theropod, true birds constitute a distinct lineage. Paleontological evidence, rather than popular narratives, provides the most reliable foundation for understanding bird evolution.

A Deist Viewpoint

References

Alegret, L., Thomas, E., & Lohmann, K. C. (2012). End-Cretaceous marine mass extinction not caused by productivity collapse. Proceedings of the National Academy of Sciences, 109(3), 728–732.
Amiot, R., Lécuyer, C., Buffetaut, E., Fluteau, F., Legendre, S., & Martineau, F. (2011). Oxygen isotope evidence for semi-aquatic habits among spinosaurid dinosaurs. Geology, 39(2), 139–142.
Bakker, R. T. (1986). The Dinosaur Heresies: New Theories Unlocking the Mystery of the Dinosaurs and Their Extinction. William Morrow.
Billings, W. D. (1987). Constraints to plant growth, reproduction, and establishment in Arctic environments. Arctic and Alpine Research, 19(4), 357–365.
Caldeira, K., & Wickett, M. E. (2003). Anthropogenic carbon and ocean pH. Nature, 425(6956), 365.
Chen, P.-J., Dong, Z.-M., & Zhen, S.-N. (1998). An exceptionally well-preserved theropod dinosaur from the Yixian Formation of China. Nature, 391(6663), 147–152.
Clarke, J. A., Tambussi, C. P., Noriega, J. I., Erickson, G. M., & Ketcham, R. A. (2005). Definitive fossil evidence for the extant avian radiation in the Cretaceous. Nature, 433(7023), 305–308.
D’Hondt, S., Donaghay, P., Zachos, J. C., Luttenberg, D., & Lindinger, M. (1998). Organic carbon fluxes and ecological recovery from the Cretaceous-Tertiary mass extinction. Science, 282(5387), 276–279.
DePalma, R. A., Burnham, D. A., Martin, L. D., Larson, P. L., & Bakker, R. T. (2015). The first giant raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation. Paleontological Contributions, 14, 1–16.
Erickson, G. M., Rauhut, O. W., Zhou, Z., Turner, A. H., Inouye, B. D., Hu, D., & Norell, M. A. (2009). Was dinosaurian physiology inherited by birds? Reconciling slow growth in Archaeopteryx. PLoS ONE, 4(10), e7390.
Erickson, G. M., Rogers, R. R., & Yerby, S. A. (2001). Dinosaurian growth patterns and rapid avian growth rates. Nature, 412(6845), 429–433.
Field, D. J., Hanson, M., Burnham, D., Wilson, L. E., Super, K., Ehret, D., ... & Bhullar, B.-A. S. (2018). Complete Ichthyornis skull illuminates mosaic assembly of the avian head. Nature, 557(7703), 96–100.
Grady, J. M., Enquist, B. J., Dettweiler-Robinson, E., Wright, N. A., & Smith, F. A. (2014). Evidence for mesothermy in dinosaurs. Science, 344(6189), 1268–1272.
Henehan, M. J., Ridgwell, A., Thomas, E., Zhang, S., Alegret, L., Schmidt, D. N., ... & Pearson, P. N. (2019). Rapid ocean acidification and protracted Earth system recovery followed the end-Cretaceous Chicxulub impact. Proceedings of the National Academy of Sciences, 116(43), 22500–22504.
Ji, Q., Currie, P. J., Norell, M. A., & Ji, S.-A. (1998). Two feathered dinosaurs from northeastern China. Nature, 393(6687), 753–761.
Kaiho, K., Oshima, N., Adachi, K., Adachi, Y., Mizukami, T., Fujibayashi, M., & Saito, R. (2016). Global climate change driven by soot at the K-Pg boundary as the cause of the mass extinction. Scientific Reports, 6, 28427.
Kring, D. A. (2007). The Chicxulub impact event and its environmental consequences at the Cretaceous–Tertiary boundary. Palaeogeography, Palaeoclimatology, Palaeoecology, 255(1-2), 4–21.
Li, Q., Gao, K.-Q., Vinther, J., Shawkey, M. D., Clarke, J. A., D’Alba, L., ... & Prum, R. O. (2012). Plumage color patterns of an extinct dinosaur. Science, 335(6073), 1365–1368.
Longrich, N. R., Tokaryk, T., & Field, D. J. (2011). Mass extinction of birds at the Cretaceous–Paleogene (K–Pg) boundary. Proceedings of the National Academy of Sciences, 108(37), 15253–15257.
Longrich, N. R., Bhullar, B.-A. S., & Gauthier, J. A. (2012). Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary. Proceedings of the National Academy of Sciences, 109(52), 21396–21401.
Markwick, P. J. (1998). Crocodilian diversity in space and time: The role of climate in paleoecology and its implication for understanding K/T extinctions. Paleobiology, 24(4), 470–497.
Marsh, O. C. (1880). Odontornithes: A Monograph on the Extinct Toothed Birds of North America. United States Geological Exploration of the Fortieth Parallel.
O’Connor, J., et al. (2025). Chicago Archaeopteryx informs on the early evolution of the avian bauplan. Nature.
Pierazzo, E., Garcia, R. R., Kinnison, D. E., Marsh, D. R., Lee-Taylor, J., & Crutzen, P. J. (2003). Ozone perturbation from medium-size asteroid impacts in the ocean. Earth and Planetary Science Letters, 214(1-2), 163–178.
Robertson, D. S., Lewis, W. M., Sheehan, P. M., & Toon, O. B. (2013). K-Pg extinction: Reevaluation of the heat-fire hypothesis. Journal of Geophysical Research: Biogeosciences, 118(1), 329–336.
Roček, Z. (1997). The early history of frogs after the Cretaceous–Tertiary boundary. Acta Palaeontologica Polonica, 42(4), 561–576.
Schulte, P., Alegret, L., Arenillas, I., Arz, J. A., Barton, P. J., Bown, P. R., ... & Willumsen, P. S. (2010). The Chicxulub asteroid impact and mass extinction at the Cretaceous–Paleogene boundary. Science, 327(5970), 1214–1218.
Soden, B. J., Wetherald, R. T., Stenchikov, G. L., & Robock, A. (2002). Global cooling after the eruption of Mount Pinatubo: A test of climate feedback by water vapor. Science, 296(5568), 727–730.
Toon, O. B., Zahnle, K., Morrison, D., Turco, R. P., & Covey, C. (1997). Environmental perturbations caused by the impacts of asteroids and comets. Reviews of Geophysics, 35(1), 41–78.
Turner, A. H., Makovicky, P. J., & Norell, M. A. (2007). Feather quill knobs in the dinosaur Velociraptor. Science, 317(5845), 1721.
Vajda, V., & McLoughlin, S. (2004). Fungal proliferation at the Cretaceous-Tertiary boundary. Science, 303(5663), 1489.
Vellekoop, J., Sluijs, A., Smit, J., Schouten, S., Weijers, J. W. H., Sinninghe Damsté, J. S., & Brinkhuis, H. (2014). Rapid short-term cooling following the Chicxulub impact at the Cretaceous–Paleogene boundary. Proceedings of the National Academy of Sciences, 111(21), 7537–7541.
Wilson, G. P. (2014). Mammalian extinction, survival, and recovery dynamics across the Cretaceous-Paleogene boundary in northeastern Montana, USA. Geological Society of America Special Papers, 503, 365–392.
Wolbach, W. S., Lewis, R. S., & Anders, E. (1985). Cretaceous extinctions: Evidence for wildfires and search for meteoritic material. Science, 230(4722), 167–170.
Xu, X., & Norell, M. A. (2004). A new troodontid dinosaur from China with avian-like sleeping posture. Nature, 431(7010), 838–841.
Xu, X., Zhou, Z., Wang, X., Kuang, X., Zhang, F., & Du, X. (2003). Four-winged dinosaurs from China. Nature, 421(6921), 335–340.
Xu, X., Currie, P., Pittman, M., Xing, L., Meng, Q., Lü, J., ... & Briggs, D. E. G. (2012). A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature, 484(7392), 92–95.
Zhang, F., Kearns, S. L., Orr, P. J., Benton, M. J., Zhou, Z., Johnson, D., ... & Zhou, Z. (2010). Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature, 463(7284), 1075–1078.
Zhou, Z., & Hou, L. (2002). The discovery and study of Mesozoic birds in China. In Chiappe, L. M., & Witmer, L. M. (Eds.), Mesozoic Birds: Above the Heads of Dinosaurs (pp. 160–183). University of California Press.