Bird Evolution Across the K–Pg Boundary and the Basal Neornithine Diversification

Atmospheric conditions are critical for a range of biological functions-locomotion among others-and long-term changes in these conditions have been identified as causal for different macroevolutionary patterns. Here we examine the influence of variations in atmospheric O2 concentration (AOC), temperature (Tair), and air density (ρair) on the power efficiency, as it relates to locomotion, during the evolutionary history of birds. Specifically, our study centers on four key evolutionary events: (1) the body mass reduction of non-avian theropods prior to the rise of birds; (2) the emergence of flapping flight in the earliest birds; (3) the divergence of basal pygostylians; and (4) the diversification of modern birds. Our results suggest that a marked increase in AOC and ρair during the Middle Jurassic-coeval with a trend in miniaturization-improved the power efficiency of the dinosaurian predecessors of birds. Likewise, an increase in these conditions is hypothesized as having played a major role in the diversification of early pygostylians during the Early Cretaceous. However, our analyses do not identify any significant paleoatmospheric effects on either the emergence of flapping flight or the early cladogenesis of modern birds. Extinct birds flew within the range of atmospheric conditions in which modern birds fly but varying past conditions influenced their flight performance. Our study thus highlights the importance of considering paleoatmospheric conditions when reconstructing the flight efficiency of the forerunners of modern birds.

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“…extinction (Penny and Phillips, 2004;Lindow, 2011)-and the development of their aerial strategies were not supported by atmospheric variation.…”

Section: Accepted Manuscriptmentioning

confidence: 88%

The effect of long-term atmospheric changes on the macroevolution of birds

et al. 2019

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A North American stem turaco, and the complex biogeographic history of modern birds

Field

Hsiang

2018

BMC Evol Biol

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BackgroundEarth’s lower latitudes boast the majority of extant avian species-level and higher-order diversity, with many deeply diverging clades restricted to vestiges of Gondwana. However, palaeontological analyses reveal that many avian crown clades with restricted extant distributions had stem group relatives in very different parts of the world.ResultsOur phylogenetic analyses support the enigmatic fossil bird Foro panarium Olson 1992 from the early Eocene (Wasatchian) of Wyoming as a stem turaco (Neornithes: Pan-Musophagidae), a clade that is presently endemic to sub-Saharan Africa. Our analyses offer the first well-supported evidence for a stem musophagid (and therefore a useful fossil calibration for avian molecular divergence analyses), and reveal surprising new information on the early morphology and biogeography of this clade. Total-clade Musophagidae is identified as a potential participant in dispersal via the recently proposed ‘North American Gateway’ during the Palaeogene, and new biogeographic analyses illustrate the importance of the fossil record in revealing the complex historical biogeography of crown birds across geological timescales.ConclusionsIn the Palaeogene, total-clade Musophagidae was distributed well outside the range of crown Musophagidae in the present day. This observation is consistent with similar biogeographic observations for numerous other modern bird clades, illustrating shortcomings of historical biogeographic analyses that do not incorporate information from the avian fossil record.Electronic supplementary materialThe online version of this article (10.1186/s12862-018-1212-3) contains supplementary material, which is available to authorized users.

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Bird Evolution Across the K–Pg Boundary and the Basal Neornithine Diversification

Cited by 2 publications

References 110 publications

The effect of long-term atmospheric changes on the macroevolution of birds

The effect of long-term atmospheric changes on the macroevolution of birds

A North American stem turaco, and the complex biogeographic history of modern birds

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